WT/DS381/AB/RW  
 
20 November 2015  
(15-6148)  Page: 1/144  
  Original: English  
 
 UNITED STATES – MEASURES CONCERNING THE IMPORTATION, 
MARKETING AND SALE OF TUNA AND TUNA PRODUCTS 
RECOURSE TO ARTICLE 21.5 OF THE DSU BY MEXICO  
AB-2015-6 
Report of the Appellate Body 
 
 
 
 WT/DS381/AB/RW 
 
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 Table of Contents 
1  INTRODUC TION ......................................................................................................... 12  
2  ARGUMENTS OF TH E PARTICIPANTS ......................................................................... 18  
3  ARGUMENTS OF THE TH IRD PARTICIPANTS .............................................................. 18  
4  ISSUES RAISED IN  THIS APPEAL ............................................................................... 18  
5  PRELIMINAR Y ISSUES ............................................................................................... 20  
5.1   Business confiden tial information ......................................................................... 20  
5.2   The scope of Arti cle 21.5 proc eedings ................................................................... 22  
6  BACKGROUND AND OVERVIEW OF THE MEASURE AT ISSUE ...................................... 24  
6.1   The amended tuna measure .................................................................................. 26  
6.1.1   The ETP large purse-seine fishery .......................................................................... 29 
6.1.2   The non-ETP purse-seine fishery ........................................................................... 31 
6.1.3   "All othe r fisheries" ............................................................................................. 32 
6.2   Principal modifications und er the amended tu na measure .................................... 32  
7  ANALYSIS OF THE APPELLATE BODY ......................................................................... 33  
7.1   Mexico's claim regarding the amended tuna measur e as a whole ......................... 33  
7.2   Article 2.1 of the TBT Agre ement .......................................................................... 40  
7.2.1  "Treatment no less favourable" und er Article 2.1 of the TBT Agreement ...................... 41 
7.2.2  Less favourable treatment – Detrimental impact ...................................................... 45 
7.2.2.1  The findings of detrimental impact in the original proceedings ................................... 47 
7.2.2.2  The Panel's findings ............................................................................................. 49 
7.2.2.3  Whether the Panel erred in its an alysis of the detrimental impact of the 
amended tuna  measure ....................................................................................... 52 
7.2.3   Less favourable treatment – Stems exclusively from a legitimate regulatory 
distinction .......................................................................................................... 58 
7.2.3.1  Whether the Panel erred in its interpretation of Article 2.1 and its articulation of 
the legal standard for determining whether the detrimental impact on imported 
products stems exclusively from a le gitimate regulato ry distinction ............................ 58 
7.2.3.2  Whether the Panel erred in its asse ssment of whether the detrimental impact of 
the amended tuna measure on Mexican tuna products stems exclusively from a legitimate regulato ry distin ction ............................................................................ 66
 
7.2.3.2.1  Preliminary observations .................................................................................. 66 
7.2.3.2.2  The eligibility criteria ....................................................................................... 70 
7.2.3.2.2.1 The Panel's findings ........................................................................................ 70 
7.2.3.2.2.2 Whether the Panel erred by misreading the findings of the Appellate Body in 
the original proceedings ................................................................................... 71 
7.2.3.2.3   The certification and trac king and verificati on requirements .................................. 74 
7.2.3.2.3.1 The Panel's findings ........................................................................................ 75 
7.2.3.2.3.2 Whether the Panel erred by failing to examine whether the different 
certification and tracking and verification requirements are "calibrated" to the risks to dolphins arising from diffe rent fishing methods in different areas 
of the oceans ................................................................................................. 78
 WT/DS381/AB/RW 
 
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 7.2.3.2.3.3 Whether the Panel erred in finding that, by virtue of the determination 
provisions, the detrimental impact does not stem exclusively from a legitimate regulato ry distin ction ........................................................................ 86
 
7.2.3.3  Whether the Panel acted inconsistently with Article 11 of the DSU .............................. 92 
7.2.3.4  Overall conclusions on the Panel's analysis under Article 2.1 of the 
TBT Agreement ................................................................................................. 102  
7.2.4   Completion of the legal analysis .......................................................................... 103  
7.3   Articles I, III, and XX of the GATT 1994 .............................................................. 116  
7.3.1   Articles I:1 and III:4 of the GA TT 1994  ................................................................ 116  
7.3.2   The chapeau of Ar ticle XX of th e GATT 1994  ......................................................... 120  
7.3.2.1  The Panel's findings ........................................................................................... 120  
7.3.2.2  Whether the Panel erred in its analysis under the chapeau of Article XX of the 
GATT 1994 ....................................................................................................... 123  
7.3.2.2.1   Discrimination between countries  where the same cond itions prevail .................... 124  
7.3.2.2.2   Arbitrary or unjustifiable discrimination ............................................................ 127  
7.3.2.2.3   Conclusion ................................................................................................... 133  
7.3.3   Completion of the legal analysis .......................................................................... 134  
7.3.3.1  Articles I:1 and III:4 of the GA TT 1994  ................................................................ 134  
7.3.3.2  Article XX of the GATT 1994 ............................................................................... 135  
8  FINDINGS AND CONCLUSI ONS ................................................................................ 142  
 WT/DS381/AB/RW 
 
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 ABBREVIATIONS USED IN THIS REPORT 
Abbreviation Description 
2013 Final Rule USDOC, National Oceanic and Atmospheric Administration (NOAA), 
Enhanced Document Requirements to Support Use of the Dolphin 
Safe Label on Tuna Products, United States Federal Register , Vol. 78, 
No. 131 (9 July 2013), pp. 40997-41004 (Panel Exhibit MEX-7) 
AIDCP Agreement on the International Dolphin Conservation Program 
(Original Panel Exhibits US-23a and MEX-11; Panel Exhibit MEX-30) 
AIDCP Tracking and 
Verification System AIDCP, Resolution to Adopt the Mo dified System for Tracking and 
Verification of Tuna (20 June 2001) (Original Panel Exhibit MEX-55; 
Panel Exhibit MEX-36) 
amended tuna measure The United States' dolphin-safe labelling regime for tuna products, 
comprising: (i) the DPCIA; (ii) Subpart H of Part 216 of CFR Title 50 
as amended by the 2013 Final Rule (implementing regulations); 
(iii) the Hogarth ruling; and (iv) any implementing guidance, 
directives, policy announcements, or any other document issued in 
relation to instruments (i) through (iii), including any modifications or 
amendments in relation to those instruments 
BCI business confidential information 
CFR United States Code of Federal Regulations  
DML dolphin mortality limits  
DPCIA Dolphin Protection Consumer Information Act of 1990, codified in USC 
Title 16, Section 1385 (Original Panel Exhibit US-5; Panel Exhibit 
MEX-8) 
DSB Dispute Settlement Body  
DSU Understanding on Rules and Procedures Governing the Settlement of 
Disputes  
ETP Eastern Tropical Pacific Ocean 
FAD(s) fish aggregating device(s) 
Form 370 NOAA, Fisheries Certificate of Origin (Panel Exhibit MEX-22) 
GATT 1994 General Agreement on Tariffs and Trade 1994 
Hogarth ruling United States Court of Appeals for the Ninth Circuit, Earth Island 
Institute et al. v. William T. Hogarth , 494 F.3d 757 (9th Cir. 2007) 
(Original Panel Exhibit MEX-31; Panel Exhibit MEX-16) 
IATTC Inter-American Tropical Tuna Commission  
IDCP International Dolphin Conservation Program 
implementing regulations USDOC, National Marine Fisheries Service/NOAA, Dolphin Safe Tuna 
Labeling,  CFR Title 50, Part 216, Subpart H (Sections 216.90-216.95) 
(Panel Exhibit US-2) 
Mexico's panel request Request for the Establishment of a Panel by Mexico pursuant to 
Article 21.5 of the DSU, WT/DS381/20 
MMPA Marine Mammal Protection Act of 1972, as amended 
NMFS National Marine Fisheries Service 
NOAA  National Oceanic and Atmospheric Administration 
original implementing regulations CFR Title 50, Sections 216.91 and 216.92 (Original Panel Exhibit 
US-6) WT/DS381/AB/RW 
 
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 Abbreviation Description 
PBR potential biological removal 
TBT Agreement Agreement on Technical Barriers to Trade 
TTFs Tuna Tracking Forms 
TTVP NMFS Tuna Tracking and Verification Program 
USC United States Code 
USDOC United States Department of Commerce 
WIO Western Indian Ocean 
Working Procedures Working Procedures for Appellate Review, WT/AB/WP/6, 
16 August 2010 
WTO World Trade Organization WT/DS381/AB/RW 
 
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 PANEL EXHIBITS CITED IN THIS REPORT 
Panel 
Exhibit Original 
Panel 
Exhibit Short Title 
(if any) Description 
 MEX-2  National Research Council, Dolphins and the 
Tuna Industry  (National Academy Press: 
Washington, D.C., 1992) 
MEX-4 MEX-91  IDCP, Scientific Advisory Board, "Updated 
Estimates of Nmin and Stock Mortality Limits", 
7th Meeting (30 October 2009), Document 
SAB-07-05 
MEX-5 MEX-117  AIDCP, 22nd Meeting of the Parties, Minutes 
(30 October 2009)  
MEX-7  2013 Final 
Rule USDOC, National Oceanic and Atmospheric 
Administration (NOAA), Enhanced Document 
Requirements to Support Use of the Dolphin 
Safe Label on Tuna Products, United States 
Federal Register , Vol. 78, No. 131 
(9 July 2013), pp. 40997-41004  
MEX-8 US-5 DPCIA Dolphin Protection Consumer Information Act of 
1990, codified in USC Title 16, Section 1385  
MEX-16 MEX-31 Hogarth ruling United States Court of Appeals for the Ninth 
Circuit, Earth Island Institute et al. v. William 
T. Hogarth , 494 F.3d 757 (9th Cir. 2007)  
MEX-20   CFR Title 50, Section 216 
MEX-30 US-23a and 
MEX-11 AIDCP Agreement on the International Dolphin 
Conservation Program  
MEX-22  Form 370 NOAA, Fisheries Certificate of Origin  
MEX-36 MEX-55 AIDCP 
Tracking and 
Verification 
System AIDCP, Resolution to Adopt the Modified System 
for Tracking and Verification of Tuna 
(20 June 2001)  
MEX-40 US-10  National Marine Fisheries Service, An Annotated 
Bibliography of Available Literature Regarding 
Cetacean Interactions with Tuna Purse-Seine Fisheries Outside of the Eastern Tropical Pacific 
Ocean , Administrative Report LJ-96-20 
(November 1996) 
MEX-81   M.N. Maunder, "Evaluating recent trends in EPO 
dolphin stocks", IATTC draft paper 
MEX-82   V.R. Restrepo, Chair's Report of the ISSF Tuna 
Dolphin Workshop held on 25-26 October 2012 
MEX-84   Programa Nacional de Aprovechamiento del 
Atún y Protección de Delfines  (National Program 
for the Utilization of Tuna and Protection of 
Dolphins), Statement of Dr Michael Dreyfus, 
Chief Researcher (28 March 2014)  WT/DS381/AB/RW 
 
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 Panel 
Exhibit Original 
Panel 
Exhibit Short Title 
(if any) Description 
MEX-115 MEX-56 AIDCP Dolphin 
Safe Certification 
Resolution AIDCP, Resolution to Establish Procedures for 
AIDCP Dolphin Safe Tuna Certification (20 June 2001)  
MEX-132   Food and Agriculture Organization, Fisheries 
Glossary, available at: 
<http://www.fao.org/fi/glossary/>  
MEX-161  Anderson, 
Cetaceans and Tuna 
Fisheries  R.C. Anderson, Cetaceans and Tuna Fisheries in 
the Western and Central Indian Ocean , 
International Pole and Line Foundation, 
Technical Report No. 2 (London, 2014) 
US-2  implementing 
regulations USDOC, National Marine Fisheries 
Service/NOAA, Dolphin Safe Tuna Labeling,  CFR 
Title 50, Part 216, Subpart H 
(Sections 216.90-216.95)  
 US-6 original 
implementing 
regulations CFR Title 50, Sections 216.91 and 216.92  
US-26 
(corrected)   IATTC, EPO Dataset 2009-2013  
US-27   IDCP, 34th Meeting of the International Review 
Panel held on 9-10 October 2003, "Effectiveness of Technical Guidelines to Prevent High Mortality 
During Sets on Large Dolphin Herds", Document 
IRP-34-10 (revised) 
US-28 US-19  B. Reilly et al., Report of the Scientific Research 
Program Under the International Dolphin 
Conservation Program Act  (2005) 
US-29   T. Gerrodette, "The Tuna-Dolphin Issue", in 
Encyclopedia of Marine Mammals , 2nd edn, 
W.F. Perrin, B. Würsig, J.G.M. Thewissen (eds.) 
(Oxford, 2009), p. 1192 
US-48 US-11  A.C. Myrick, Jr. and P.C. Perkins, 
"Adrenocortical color darkness and correlates as 
indicators of continuous acute premortem stress 
in chased and purse-seine captured male 
dolphins" (1995) 2 Pathophysiology  
US-49   IATTC, Initial assignment of DMLs for 2008 (21 
November 2007) 
US-127   Tables Summarizing Fishery-by-Fishery 
Evidence on the Record WT/DS381/AB/RW 
 
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 CASES CITED IN THIS REPORT 
Short Title Full Case Title and Citation 
Argentina – Hides and 
Leather  Panel Report, Argentina – Measures Affecting th e Export of Bovine Hides and 
Import of Finished Leather , WT/DS155/R and Corr.1, adopted 16 February 
2001, DSR 2001:V, p. 1779 
Australia – Salmon  Appellate Body Report, Australia – Measures Affecting Importation of Salmon , 
WT/DS18/AB/R, adopted 6 November 1998, DSR 1998:VIII, p. 3327 
Brazil – Retreaded Tyres  Appellate Body Report, Brazil – Measures Affecting Imports of Retreaded 
Tyres , WT/DS332/AB/R, adopted 17 December 2007, DSR 2007:IV, p. 1527 
Canada – Aircraft  Appellate Body Report, Canada – Measures Affecting the Export of Civilian 
Aircraft , WT/DS70/AB/R, adopted 20 Augu st 1999, DSR 1999:III, p. 1377 
Canada – Aircraft 
(Article 21.5 – Brazil)  Appellate Body Report, Canada – Measures Affecting the Export of Civilian 
Aircraft – Recourse by Brazil to Article 21.5 of the DSU , WT/DS70/AB/RW, 
adopted 4 August 2000, DSR 2000:IX, p. 4299 
Canada – Renewable Energy 
/ Canada – Feed-in Tariff 
Program  Appellate Body Reports, Canada – Certain Measures Affecting the Renewable 
Energy Generation Sector / Canada – Me asures Relating to the Feed-in Tariff 
Program , WT/DS412/AB/R / WT/DS426/AB/R, adopted 24 May 2013, DSR 
2013:I, p. 7 
Chile – Price Band System  Appellate Body Report, Chile – Price Band System and Safeguard Measures 
Relating to Certain Agricultural Products , WT/DS207/AB/R, adopted 23 October 
2002, DSR 2002:VIII, p. 3045 (Corr. 1, DSR 2006:XII, p. 5473) 
Chile – Price Band System 
(Article 21.5 – Argentina)  Appellate Body Report, Chile – Price Band System and Safeguard Measures 
Relating to Certain Agricultural Products  – Recourse to Article 21.5 of the DSU 
by Argentina , WT/DS207/AB/RW, adopted 22 May 2007, DSR 2007:II, p. 513 
China – HP-SSST (Japan) / 
China – HP-SSST (EU)  Appellate Body Reports, China – Measures Imposing Anti-Dumping Duties on 
High-Performance Stainless Steel Seamless Tubes ("HP-SSST") from Japan / China – Measures Imposing Anti-Dum ping Duties on High-Performance 
Stainless Steel Seamle ss Tubes ("HP-SSST") from the European Union , 
WT/DS454/AB/R and Add.1 / WT/DS460/AB /R and Add.1, adopted 28 October 
2015 
China – Publications and 
Audiovisual Products  Appellate Body Report, China –  Measures Affecting Trading Rights and 
Distribution Services for Certain Publ ications and Audiovisual Entertainment 
Products , WT/DS363/AB/R, adopted 19 January 2010, DSR 2010:I, p. 3 
China – Rare Earths  Appellate Body Reports, China – Measures Related to the Exportation of Rare 
Earths, Tungsten, and Molybdenum , WT/DS431/AB/R / WT/DS432/AB/R / 
WT/DS433/AB/R, adopted 29 August 2014 
China – Raw Materials  Appellate Body Reports, China – Measures Related to the Exportation of 
Various Raw Materials , WT/DS394/AB/R / WT/DS 395/AB/R / WT/DS398/AB/R, 
adopted 22 February 2012, DSR 2012:VII, p. 3295 
Colombia – Ports of Entry  Panel Report, Colombia – Indicative Prices and Restrictions on Ports of Entry , 
WT/DS366/R and Corr.1, adopted 20 May 2009, DSR 2009:VI, p. 2535 
Dominican Republic – Import 
and Sale of Cigarettes  Appellate Body Report, Dominican Republic – Measures Affecting the 
Importation and Internal Sale of Cigarettes , WT/DS302/AB/R, adopted 19 May 
2005, DSR 2005:XV, p. 7367 
EC – Asbestos  Appellate Body Report, European Communities – Meas ures Affecting Asbestos 
and Asbestos-Containing Products , WT/DS135/AB/R, adopted 5 April 2001, 
DSR 2001:VII, p. 3243 
EC – Bananas III  Appellate Body Report, European Communities – Regime for the Importation, 
Sale and Distribution of Bananas , WT/DS27/AB/R, adopted 25 September 
1997, DSR 1997:II, p. 591 
EC – Bed Linen 
(Article 21.5 – India)  Appellate Body Report, European Communities – An ti-Dumping Duties on 
Imports of Cotton-Type Bed Linen from In dia – Recourse to Article 21.5 of the 
DSU by India , WT/DS141/AB/RW, adopted 24 April 2003, DSR 2003:III, 
p. 965 WT/DS381/AB/RW 
 
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 Short Title Full Case Title and Citation 
EC – Fasteners (China)  Appellate Body Report, European Communities – Definitive Anti-Dumping 
Measures on Certain Iron or  Steel Fasteners from China , WT/DS397/AB/R, 
adopted 28 July 2011, DSR 2 011:VII, p. 3995 
EC – Fasteners (China)  Panel Report, European Communities – Definiti ve Anti-Dumping Measures on 
Certain Iron or Stee l Fasteners from China , WT/DS397/R and Corr.1, adopted 
28 July 2011, as modified by Appellate Body Report WT/DS397/AB/R, DSR 2011:VIII, p. 4289 
EC – Hormones  Appellate Body Report, EC Measures Concerning Meat and Meat Products 
(Hormones) , WT/DS26/AB/R, WT/DS48/AB/R, adopted 13 February 1998, 
DSR 1998:I, p. 135 
EC – Sardines  Appellate Body Report, European Communities – Trade Description of 
Sardines , WT/DS231/AB/R, adopted 23 Octo ber 2002, DSR 2002:VIII, p. 3359 
EC – Seal Products  Appellate Body Reports, European Communities – Measures Prohibiting the 
Importation and Marketing of Seal Products , WT/DS400/AB/R / 
WT/DS401/AB/R, adopted 18 June 2014 
EC – Selected Customs 
Matters  Appellate Body Report, European Communities – Selected Customs Matters , 
WT/DS315/AB/R, adopted 11 December 2006, DSR 2006:IX, p. 3791 
EC – Tariff Preferences  Appellate Body Report, European Communities – Conditions for the Granting of 
Tariff Preferences to Developing Countries , WT/DS246/AB/R, adopted 20 April 
2004, DSR 2004:III, p. 925 
EC – Tube or Pipe Fittings  Appellate Body Report, European Communities – An ti-Dumping Duties on 
Malleable Cast Iron Tube or  Pipe Fittings from Brazil , WT/DS219/AB/R, 
adopted 18 August 2003, DSR 2003:VI, p. 2613 
EC and certain member 
States – Large Civil Aircraft  Panel Report, European Communities and Certai n Member States – Measures 
Affecting Trade in Large Civil Aircraft , WT/DS316/R, adopted 1 June 2011, as 
modified by Appellate Body Report, WT/DS316/AB/R, DSR 2011:II, p. 685 
Japan – Agricultural 
Products II  Appellate Body Report, Japan – Measures Affecting Agricultural Products , 
WT/DS76/AB/R, adopted 19 March 1999, DSR 1999:I, p. 277 
Japan – Alcoholic 
Beverages II  Appellate Body Report, Japan – Taxes on Alcoholic Beverages , WT/DS8/AB/R, 
WT/DS10/AB/R, WT/DS11/AB/R, adopted 1 November 1996, DSR 1996:I, 
p. 97 
Japan – Apples  Appellate Body Report, Japan – Measures Affecting the Importation of Apples , 
WT/DS245/AB/R, adopted 10 December 2003, DSR 2003:IX, p. 4391 
Japan – DRAMs (Korea)  Appellate Body Report, Japan – Countervailing Duties on Dynamic Random 
Access Memories from Korea , WT/DS336/AB/R and Corr.1, adopted 
17 December 2007, DSR 2007:VII, p. 2703 
Korea – Alcoholic Beverages  Appellate Body Report, Korea – Taxes on Alcoholic Beverages , WT/DS75/AB/R, 
WT/DS84/AB/R, adopted 17 February 1999, DSR 1999:I, p. 3 
Korea – Dairy  Appellate Body Report, Korea – Definitive Safeguar d Measure on Imports of 
Certain Dairy Products , WT/DS98/AB/R, adopted 12 January 2000, 
DSR 2000:I, p. 3 
Korea – Various Measures on 
Beef Appellate Body Report, Korea – Measures Affecting Imports of Fresh, Chilled 
and Frozen Beef , WT/DS161/AB/R, WT/DS169/AB/R, adopted 10 January 
2001, DSR 2001:I, p. 5 
Mexico – Anti-Dumping 
Measures on Rice  Appellate Body Report, Mexico – Definitive Anti-Dumping Measures on Beef 
and Rice, Complaint with Respect to Rice , WT/DS295/AB/R, adopted 
20 December 2005, DSR 2005:XXII, p. 10853 
Mexico – Corn Syrup 
(Article 21.5 – US)  Appellate Body Report, Mexico – Anti-Dumping Investigation of High Fructose 
Corn Syrup (HFCS) from the United Stat es – Recourse to Article 21.5 of the 
DSU by the United States , WT/DS132/AB/RW, adopted 21 November 2001, 
DSR 2001:XIII, p. 6675 
Mexico – Taxes on Soft 
Drinks Panel Report, Mexico – Tax Measures on Soft  Drinks and Other Beverages , 
WT/DS308/R, adopted 24 March 2006, as modified by Appellate Body Report 
WT/DS308/AB/R, DSR 2006:I, p. 43 WT/DS381/AB/RW 
 
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 Short Title Full Case Title and Citation 
Thailand – Cigarettes 
(Philippines)  Appellate Body Report, Thailand – Customs and Fiscal  Measures on Cigarettes 
from the Philippines , WT/DS371/AB/R, adopted 15 July 2011, DSR 2011:IV, 
p. 2203 
Thailand – H-Beams Appellate Body Report, Thailand – Anti-Dumping Duties on Angles, Shapes and 
Sections of Iron or Non-Alloy Steel and H-Beams from Poland , 
WT/DS122/AB/R, adopted 5 April 2001, DSR 2001:VII, p. 2701 
US – Carbon Steel  Appellate Body Report, United States – Countervai ling Duties on Certain 
Corrosion-Resistant Carbon Stee l Flat Products from Germany , 
WT/DS213/AB/R and Corr.1, adopted 19 December 2002, DSR 2002:IX, p. 3779 
US – Clove Cigarettes  Appellate Body Report, United States – Measures Affecting the Production and 
Sale of Clove Cigarettes , WT/DS406/AB/R, adopted 24 April 2012, DSR 2012: 
XI, p. 5751 
US – Continued Zeroing  Appellate Body Report, United States – Continued Ex istence and Application of 
Zeroing Methodology , WT/DS350/AB/R, adopted 19 February 2009, 
DSR 2009:III, p. 1291 
US – COOL  Appellate Body Reports, United States – Certain Country of Origin Labelling 
(COOL) Requirements , WT/DS384/AB/R / WT/DS386/AB/R, adopted 23 July 
2012, DSR 2012:V, p. 2449 
US – COOL  Panel Reports, United States – Certain Country of Origin Labelling (COOL) 
Requirements , WT/DS384/R / WT/DS386/R, adopted 23 July 2012, as modified 
by Appellate Body Reports WT/DS 384/AB/R / WT/DS386/AB/R, DSR 2012:VI, 
p. 2745 
US – COOL 
(Article 21.5 – Canada and 
Mexico)  Appellate Body Reports, United States – Certain Country of Origin Labelling 
(COOL) Requirements – Recourse to Article 21.5 of the DSU by Canada and 
Mexico , WT/DS384/AB/RW / WT/DS386/AB/RW, adopted 29 May 2015 
US – COOL 
(Article 21.5 – Canada and Mexico)  Panel Reports, United States – Certain Country of Origin Labelling (COOL) 
Requirements – Recourse to Article 21.5 of the DSU by Canada and Mexico , 
WT/DS384/RW and Add.1 / WT/DS386/RW and Add.1, adopted 29 May 2015, as modified by Appellate Body Reports WT/DS384/AB/RW / WT/DS386/AB/RW 
US – FSC 
(Article 21.5 – EC)  Appellate Body Report, United States – Tax Treatment for "Foreign Sales 
Corporations" – Recourse to Article 21.5 of the DSU by the European 
Communities , WT/DS108/AB/RW, adopted 29 January 2002, DSR 2002:I, 
p. 55 
US – FSC 
(Article 21.5 – EC II)  Appellate Body Report, United States – Tax Treatment for "Foreign Sales 
Corporations" – Second Recourse to Ar ticle 21.5 of the DSU by the European 
Communities , WT/DS108/AB/RW2, adopted 14 March 2006, DSR 2006:XI, 
p. 4721 
US – Gambling  Appellate Body Report, United States – Measures Affecting the Cross-Border 
Supply of Gambling and Betting Services , WT/DS285/AB/R, adopted 20 April 
2005, DSR 2005:XII, p. 5663 (Corr.1, DSR 2006:XII, p. 5475) 
US – Gasoline  Appellate Body Report, United States – Standards for Reformulated and 
Conventional Gasoline , WT/DS2/AB/R, adopted 20 May 1996, DSR 1996:I, p. 3 
US – Large Civil Aircraft 
(2nd complaint)  Appellate Body Report, United States – Measures Affecting Trade in Large Civil 
Aircraft (Second Complaint) , WT/DS353/AB/R, adopted 23 March 2012, DSR 
2012:I, p. 7 
US – Oil Country Tubular 
Goods Sunset Reviews  Appellate Body Report, United States – Sunset Reviews of Anti-Dumping 
Measures on Oil Country Tubular Goods from Argentina , WT/DS268/AB/R, 
adopted 17 December 2004, DSR 2004:VII, p. 3257 
US – Oil Country Tubular 
Goods Sunset Reviews 
(Article 21.5 – Argentina)  Appellate Body Report, United States – Sunset Reviews of Anti-Dumping 
Measures on Oil Country Tubular G oods from Argentina – Recourse to 
Article 21.5 of the DSU by Argentina , WT/DS268/AB/RW, adopted 11 May 
2007, DSR 2007:IX, p. 3523 
US – Section 337 Tariff Act  GATT Panel Report, United States Section 337 of the Tariff Act of 1930 , 
L/6439, adopted 7 November 1989, BISD 36S, p. 345 WT/DS381/AB/RW 
 
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 Short Title Full Case Title and Citation 
US – Shrimp  Appellate Body Report, United States – Import Proh ibition of Certain Shrimp 
and Shrimp Products , WT/DS58/AB/R, adopted 6 November 1998, 
DSR 1998:VII, p. 2755 
US – Shrimp 
(Article 21.5 – Malaysia)  Appellate Body Report, United States – Import Proh ibition of Certain Shrimp 
and Shrimp Products – Recourse to Article 21.5 of the DSU by Malaysia , 
WT/DS58/AB/RW, adopted 21 November 2001, DSR 2001:XIII, p. 6481 
US – Softwood Lumber IV 
(Article 21.5 – Canada)  Appellate Body Report, United States – Final Countervailing Duty 
Determination with Respect to Cert ain Softwood Lumber from Canada  
– Recourse by Canada to Article 21.5 of the DSU , WT/DS257/AB/RW, adopted 
20 December 2005, DSR 2005:XXIII, p. 11357 
US – Softwood Lumber VI 
(Article 21.5 – Canada)  Appellate Body Report, United States – Investigation of the International Trade 
Commission in Softwood Lumber from Ca nada – Recourse to Article 21.5 of 
the DSU by Canada , WT/DS277/AB/RW, adopted 9 May 2006, and Corr.1, 
DSR 2006:XI, p. 4865 
US – Tuna (EEC) GATT Panel Report, United States – Restrict ions on Imports of Tuna , DS29/R, 
16 June 1994, unadopted 
US – Tuna (Mexico)  GATT Panel Report, United States – Restrict ions on Imports of Tuna , DS21/R, 
3 September 1991, unadopted, BISD 39S, p. 155 
US – Tuna II (Mexico)  Appellate Body Report, United States – Measures Concerning the Importation, 
Marketing and Sale of Tuna and Tuna Products , WT/DS381/AB/R, adopted 
13 June 2012, DSR 2012:IV, p. 1837 
US – Tuna II (Mexico)  Panel Report, United States – Measures Concerning the Importation, Marketing 
and Sale of Tuna and Tuna Products , WT/DS381/R, adopted 13 June 2012, as 
modified by Appellate Body Report WT/DS381/AB/R, DSR 2012:IV, p. 2013 
US – Upland Cotton 
(Article 21.5 – Brazil)  Appellate Body Report, United States – Subsidies on Upland Cotton – Recourse 
to Article 21.5 of the DSU by Brazil , WT/DS267/AB/RW, adopted 20 June 
2008, DSR 2008:III, p. 809 
US – Wheat Gluten  Appellate Body Report, United States – Definitive  Safeguard Measures on 
Imports of Wheat Gluten fro m the European Communities , WT/DS166/AB/R, 
adopted 19 January 2001, DSR 2001:II, p. 717 
US – Wool Shirts and 
Blouses  Appellate Body Report, United States – Measure A ffecting Imports of Woven 
Wool Shirts and Blouses from India , WT/DS33/AB/R, adopted 23 May 1997, 
and Corr.1, DSR 1997:I, p. 323 
US – Zeroing (EC)  
(Article 21.5 – EC)  Appellate Body Report, United States – Laws, Regulations and Methodology for 
Calculating Dumping Margins ("Zeroing") – Recourse to Article 21.5 of the DSU by the European Communities , WT/DS294/AB/RW and Corr.1, adopted 
11 June 2009, DSR 2009:VII, p. 2911 WT/DS381/AB/RW 
 
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 WORLD TRADE ORGANIZATION  
APPELLATE BODY 
  
United States – Measures Concerning the 
Importation, Marketing and Sale of Tuna and Tuna Products 
 
Recourse to Article 21.5 of the DSU by Mexico  
 
United States, Appellant/Appellee  
Mexico, Other Appellant/Appellee  
 
Australia, Third Participant  
Canada, Third Participant  
China, Third Participant  
European Union, Third Participant  
Guatemala, Third Participant  
Japan, Third Participant  
Korea, Third Participant  
New Zealand, Third Participant  
Norway, Third Participant  
Thailand, Third Participant  AB-2015-6 
 Appellate Body Division:  
 
Servansing, Presiding Member Bhatia, Member 
Zhang, Member 
 
 
 1  INTRODUCTION 
1.1.  The United States and Mexico each appeals certain issues of law and legal interpretations 
developed in the Panel Report, United States – Measures Concerning the Importation, Marketing 
and Sale of Tuna and Tuna Products – Recourse to Article 21.5 of the DSU by Mexico .
1 The Panel 
was established pursuant to Article 21.5 of the Understanding on Rules and Procedures Governing 
the Settlement of Disputes (DSU) to consider a complaint by Mexico2 concerning the alleged failure 
of the United States to comply with the recommendations and rulings of the Dispute 
Settlement Body (DSB) in the original proceedings in United States – Measures Concerning the 
Importation, Marketing and Sale of Tuna and Tuna Products .3 
1.2.  This dispute concerns the United States' labe lling regime for "dolphin-safe" tuna products. In 
the original proceedings, Mexico raised claims under the General Agreement on Tariffs and 
Trade 1994 (GATT 1994) and the Agreement on Te chnical Barriers to Trade (TBT Agreement) 
challenging the consistency with these Agreements of certain measures imposed by the United States on the importation, marketing, and sale of tuna and tuna products.
4 Specifically, 
Mexico challenged: the Dolphin Protection Consumer Information Act of 1990, codified in 
United States Code , Title 16, Section 13855 (DPCIA); United States Code of Federal Regulations 
(CFR), Title 50, Sections 216.91 and 216.92 (original implementing regulations)6; and a ruling by 
a US Federal Appeals Court in Earth Island Institute v. Hogarth7 (Hogarth ruling).8 The original 
                                               
1 WT/DS381/RW, 14 April 2015. 
2 Request for the Establishment of a Panel by Mexico pursuant to Article 21.5 of the DSU, WT/DS381/20 
(Mexico's panel request). 
3 The recommendations and rulings of the DSB resu lted from the adoption, on 13 June 2012, by the 
DSB of the Appellate Body report (WT/DS381/ AB/R) and the panel repo rt (WT/DS381/R) in US – Tuna II 
(Mexico) . In this Report, we refer to the panel that considered the original complaint brought by Mexico as the 
"original panel" and to its report  as the "original panel report". 
4 In the course of the original proceedings, Mexico cl arified that its claims unde r Articles I:1 and III:4 of 
the GATT 1994 and Article 2.1 of the TBT Agreement were made only in relation to tuna products, and not 
tuna. For that reason, the original panel limited its findings in this respect to tuna products. (Original Panel Report, para. 6.10) 
5 Original Panel Exhibit US-5; Panel Exhibit MEX-8. 
6 Original Panel Exhibit US-6. 
7 United States Court of A ppeals for the Ninth Circuit, Earth Island Institute et al. v. William T. Hogarth , 
494 F.3d 757 (9th Cir. 2007) (Original Panel Exhibit MEX-31; Panel Exhibit MEX-16). 
8 Panel Report, para. 1.10 (referri ng to Appellate Body Report, US – Tuna II (Mexico) , para. 172). WT/DS381/AB/RW 
 
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 panel and the Appellate Body referred to these measures, collectively9, as the "measure at issue" 
or the "US dolphin-safe labelling provisions".10 In these compliance proceedings, we refer to them 
as the "original tuna measure". 
1.3.  The original tuna measure specified the conditions to be fulfilled in order for tuna products 
sold in the United States to be labelled "dolphin-safe" or to make similar claims on their labels.11 
The specific conditions varied depending on the fishing method by which tuna contained in the tuna product was harvested, the area of the oc ean where the tuna was caught, and the type of 
vessel used.
12 The original tuna measure did not make the use of a dolphin-safe label obligatory 
for the importation or sale of tuna products in the United States13, although the preferences of 
retailers and consumers are such that the dolphin-safe label has "significant commercial value", and access to that label constitutes an "advantage" on the US market for tuna products.
14  
1.4.  The original panel found that the US "d olphin-safe" labelling provisions constituted a 
"technical regulation" within the meaning of Annex 1.1 to the TBT Agreement.15 With respect to 
Mexico's claim that the original tuna measure was inconsistent with Article 2.1 of the 
TBT Agreement, the original panel found that Mexico had failed to establish that the measure 
accorded treatment less favourable to Mexican tuna products than to US tuna products and tuna products originating in other countries.
16 The panel therefore concluded that the measure was not 
inconsistent with the United States' obligations under Article 2.1.17 The original panel found, 
however, that the original tuna measure was more trade restrictive than necessary to fulfil its legitimate objectives, taking account of the risks non-fulfilment would create, and concluded for that reason that the measure was inconsistent with Article 2.2 of the TBT Agreement.
18 With 
respect to Mexico's claim under Article 2.4 of the TBT Agreement, the original panel found that the 
Agreement on the International Dolphin Conservation Program19 (AIDCP) dolphin- safe definition 
and certification were a relevant international standard20, but that Mexico had failed to prove that 
this standard was an effective and appropriate mean s to fulfil the United States' objectives at its 
chosen level of protection.21 Therefore, the panel found that the original tuna measure was not 
inconsistent with Article 2.4.22 The original panel decided to exercise judicial economy with respect 
to Mexico's claims under Articles I:1 and III:4 of the GATT 1994.23  
1.5.  On appeal, the Appellate Body found that the original panel did not err in characterizing the 
original tuna measure as a "technical regulation" within the meaning of Annex 1.1 to the TBT Agreement.
24 The Appellate Body found, however, that the original panel had erred in its 
interpretation and application of the phrase "treatment no less favourable" in Article 2.1 of the 
TBT Agreement. The Appellate Body reversed the panel's finding that the US dolphin-safe labelling provisions were not inconsistent with Article 2. 1 of the TBT Agreement, and found, instead, that 
the dolphin-safe labelling provisions were inconsistent with that provision.
25 Furthermore, the 
                                               
9 The original panel and the Appellate Body considered  it appropriate to treat these legal instruments as 
a single measure for purposes of analysin g Mexico's claims and reaching findings. 
10 Panel Report, para. 3.1. See also Appellate Body Report, US – Tuna II (Mexico) , paras. 2 and 172 and 
fn 357 thereto. 
11 Appellate Body Report, US – Tuna II (Mexico) , para. 172; Original Panel Report, para. 2.2. Under the 
original tuna measure, only tuna products meeting the specified conditions could be labelled as "dolphin-safe", and use of this term, as well as any reference to dolp hins, porpoises, or marine mammals on the label of a 
tuna product, was prohibited if the tuna contained therein did not comply with the applicable labelling 
conditions. (Appellate Body Report, US – Tuna II (Mexico) , paras. 172, 180, and 193; Original Panel Report, 
paras. 7.124 and 7.143-7.144) 
12 Original Panel Report, paras. 2.7-2.8; Appellate Body Report, US – Tuna II (Mexico) , para. 172. 
13 Appellate Body Report, US – Tuna II (Mexico) , para. 172. 
14 Appellate Body Report, US – Tuna II (Mexico) , para. 233 (referring to Original Panel Report, 
paras. 7.289-7.291). The factual aspects of the original proceedings are set forth in greater detail in paragraphs 2.1-2.41 of the original panel report, and paragraphs 172-177 of the Appellate Body report. 
15 Original Panel Report, paras. 7.62, 7.78, and 7.145. 
16 Original Panel Report, para. 7.374. 
17 Original Panel Report, para. 8.1(a). 
18 Original Panel Report, paras. 7.620 and 8.1(b). 
19 Original Panel Exhibits US-23a and MEX-11; Panel Exhibit MEX-30. 
20 Original Panel Report, para. 7.707. 
21 Original Panel Report, para. 7.740. 
22 Original Panel Report, para. 8.1(c). 
23 Original Panel Report, paras. 7.748 and 8.2. 
24 Appellate Body Report, US – Tuna II (Mexico) , paras. 199 and 407(a). 
25 Appellate Body Report, US – Tuna II (Mexico) , paras. 299 and 407(b). WT/DS381/AB/RW 
 
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 Appellate Body found that the original panel had erred in concluding that the original tuna measure 
was more trade restrictive than necessary to fulfil the United States' legitimate objectives, taking account of the risks non-fulfilment would create . Therefore, the Appellate Body reversed the 
panel's finding that the original tuna measure was inconsistent with Article 2.2 of the 
TBT Agreement.
26 The Appellate Body also reversed the panel's finding that the AIDCP 
dolphin-safe definition and certification constituted a relevant international standard within the meaning of Article 2.4 of the TBT Agreement, whil e leaving undisturbed the panel's finding that the 
original tuna measure was not inconsistent with Article 2.4 of the TBT Agreement.
27 Finally, the 
Appellate Body found that the original panel acte d inconsistently with Article 11 of the DSU in 
deciding to exercise judicial economy with respect to Mexico's claims under Articles I:1 and III:4 of the GATT 1994.
28 The Appellate Body recommended that the DSB request the United States to 
bring its measure into conformity with its obligations under the TBT Agreement.29 
1.6.  On 13 June 2012, the DSB adopted the original panel and Appellate Body reports. 
On 2 August 2012, Mexico and the United States informed the DSB that additional time was 
required to discuss a mutually agreed reasonable period of time for the United States to implement 
the recommendations and rulings of the DSB.30 On 17 September 2012, Mexico and the 
United States informed the DSB that they had agreed on a reasonable period of time of 13 months 
from 13 June 2012. The reasonable period of time expired on 13 July 2013.31 
1.7.  On 9 July 2013, the United States published in its Federal Register  a legal instrument entitled 
"Enhanced Document Requirements to Support Use of the Dolphin Safe Label on Tuna Products"32 
(2013 Final Rule).33 The 2013 Final Rule made certain changes to Sections 216.91 and 216.93 of 
CFR Title 50.34 Both the DPCIA and the Hogarth ruling remained unchanged.35 According to the 
United States, the 2013 Final Rule constitutes the measure taken to comply with the DSB's recommendations and rulings pursuant to Article 21.5 of the DSU.
36 
1.8.  Mexico considers that the United States has not brought its labelling regime for 
"dolphin-safe" tuna products into compliance with the DSB's recommendations and rulings, and that the regime remains inconsistent with the United States' obligations under the covered 
agreements.
37 On 2 August 2013, Mexico and the United States informed the DSB of their Agreed 
Procedures under Articles 21 and 22 of the DSU38 and, on 14 November 2013, Mexico requested 
the establishment of a panel under Articles 6 and 21.5 of the DSU, Article 14 of the TBT Agreement, and Article XXIII of the GATT 1994.
39  
                                               
26 Appellate Body Report, US – Tuna II (Mexico) , paras. 331 and 407(c). The Appellate Body, however, 
upheld the original panel's conclusion that the United States' objective of "contributing to the protection of 
dolphins, by ensuring that the US mark et is not used to encourage fishing fl eets to catch tuna in a manner that 
adversely affects dolphins", was a legi timate objective within the meaning of Article 2.2 of the TBT Agreement. 
Furthermore, the Appellate Body rejected  Mexico's request to find the origin al tuna measure to be inconsistent 
with Article 2.2 of the TBT Agreement based on the original panel's finding that the measure did not entirely fulfil its objectives. (Ibid., paras. 342 and 407(d)-(e)) 
27 Appellate Body Report, US – Tuna II (Mexico) , paras. 401 and 407(f). 
28 Appellate Body Report, US – Tuna II (Mexico) , paras. 405 and 407(g). 
29 Appellate Body Report, US – Tuna II (Mexico) , para. 408. 
30 Panel Report, para. 1.12 (referring  to Communication from Mexico and the United States concerning 
Article 21.3(c) of the DSU, WT/DS381/16). 
31 Panel Report, para. 1.12 (referring to Agreemen t under Article 21.3(b) of the DSU, WT/DS381/17). 
32 US Department of Commerce (USDOC), National  Oceanic and Atmospheric Administration (NOAA), 
Enhanced Document Requirements to Support Use of the Dolphin Safe Label on Tuna Products, United States 
Federal Register , Vol. 78, No. 131 (9 July 2013), pp. 40997-41004 (Panel Exhibit MEX-7). 
33 Panel Report, para. 1.13 (referring to United States' first written submission to the Panel, para. 10). 
34 Section 216.92 of the original implementing regulations was not amended by the 2013 Final Rule. 
(Panel Report, paras. 3.32 and 3.39) 
35 Panel Report, para. 3.32. 
36 Panel Report, para. 1.13. 
37 Mexico's panel request, p. 2. 
38 WT/DS381/19. The parties agreed, inter alia , that, in the event that the DSB, following a proceeding 
under Article 21.5 of the DSU, rules that a measure taken to comply does not exist or is inconsistent with a WTO covered agreement, Mexico may request authorizatio n to suspend the application of concessions or other 
obligations under the covered agreements to the United States pursuant to Article 22 of the DSU and that the 
United States will not assert that Mexico is precluded from obtaining such authorization on the ground that the 
request was made outside the 30-day time period specified in Article 22.6 of the DSU. 
39 WT/DS381/20. WT/DS381/AB/RW 
 
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 1.9.  In its panel request, Mexico indicated that the "measure taken to comply with the 
recommendations and rulings" of the DSB, he reinafter referred to as the "amended tuna 
measure", comprises: (i) the DPCIA; (ii) Subpart H of Part 216 of CFR Title 50 as amended by the 2013 Final Rule
40 (implementing regulations); (iii) the Hogarth ruling; and (iv) any implementing 
guidance, directives, policy announcements, or any other document issued in relation to 
instruments (i) through (iii), including any modifications or amendments in relation to those instruments.
41 Mexico claimed that the amended tuna measure is still inconsistent with Article 2.1 
of the TBT Agreement, and with Articles I:1 and III:4 of the GATT 1994.42 On this basis, Mexico 
requested the Panel to find that the United States has failed to comply with the recommendations and rulings adopted by the DSB.
43 
1.10.  The Panel Report was circulated to Members of the World Trade Organization (WTO) 
on 14 April 2015. Before proceeding to the merits of the case, the Panel addressed several 
preliminary issues.44 The Panel rejected two arguments made by the United States relating to the 
scope of the Panel's jurisdiction in these Article 21.5 proceedings, namely: (i) that the scope of the 
Panel's review was limited to the measure taken to comply – the 2013 Final Rule – rather than 
extending to the amended tuna measure as a whole; and (ii) that the Panel could not entertain Mexico's claims relating to three elements of the amended tuna measure – the eligibility criteria 
for the dolphin-safe label, the different tracking and verification requirements, and the different 
observer or certification requirements – because these elements were unchanged from the original tuna measure, and were not found by the Appellate  Body to be WTO-inconsistent in the original 
proceedings. The Panel considered that the legal question before it was whether the amended tuna 
measure, including the 2013 Final Rule, brought the United States into compliance with 
WTO law
45, and that it had jurisdiction to consider all of Mexico's claims, including as they related 
to the eligibility criteria, the certification requirements, and the tracking and verification 
requirements.46 In addition, at the outset of its analysis of Mexico's claim under Article 2.1 of the 
TBT Agreement, in the light of the findings made in the original proceedings, as well as the agreement of both parties, the Panel accepted that the US dolphin-safe labelling regime is a 
"technical regulation" for purposes of the TBT Agreement, and that the relevant tuna products are 
"like".
47  
                                               
40 USDOC, National Marine Fisheries Service/NOAA, Dolphin Safe Tuna Labeling,  CFR Title 50, Part 216, 
Subpart H (Sections 216.90-216.95) as amended (Panel Exhibit US-2). 
41 Panel Report, para. 2.1. 
42 Panel Report, para. 2.2. Mexico also claimed that the amended t una measure nullifies or impairs 
benefits that accrue to Mexico under the GATT 1994 with in the meaning of Article XXIII:1(b) of the GATT 1994. 
43 Panel Report, para. 2.3 (referring to Mexico's first written submission to the Panel, para. 331). 
44 One procedural issue addressed by the Panel was the European Union's request for enhanced 
third-party rights. After considering the request and consulting with the parties, the Panel decided to decline the request. (Panel Report, para. 1.8) 
45 Panel Report, paras. 7.24 and 7.43. The Panel stated  that such a task necessarily required it to 
consider not only the contents of the 2013 Final Rule itself, but also to examine how the 2013 Final Rule interacts (or does not interact) with the other elemen ts that make up the amended tuna measure. (Ibid., 
para. 7.23) 
46 Panel Report, para. 7.43. The Panel disagreed with the United States that the 2013 Final Rule is 
"separable from the rest of the tuna measure". The Pa nel instead expressed the view that the 2013 Final Rule 
is "an integral component of the amended tuna measure" and "the fact that it adds  new requirements rather 
than changing pre-existing re quirements … does not have the effect of removing the rest of the tuna measure, 
which was the object of the DSB's rulings and recommendations, from [the Panel's] jurisdiction." (Ibid., para. 7.41 (fn omitted)) 
47 Panel Report, para. 7.71 (referring to Original Panel Report, para. 7.251; Appellate Body Report,  
US – Tuna II  (Mexico) , para. 202; Mexico's first written submission to the Panel, paras. 205 and 208; 
United States' first written submission to the Panel, para. 181; and second written submission to the Panel, para. 181). WT/DS381/AB/RW 
 
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 1.11.  In its Report, the Panel made the following findings with respect to the "eligibility criteria", 
the "certification requirements", and the "trackin g and verification requirements" in the amended 
tuna measure48: 
a. with respect to Mexico's claims under Article 2.1 of the TBT Agreement: 
i. the eligibility criteria in the amended tuna measure do not accord less favourable 
treatment to Mexican tuna and tuna products than that accorded to like products from the United States and to like products originating in any other country, and are 
thus consistent with Article 2.1 of the TBT Agreement
49;  
ii. the different certification requirements in the amended tuna measure accord less 
favourable treatment to Mexican tuna and tuna products than that accorded to like products from the United States and to like products originating in any other country, 
in violation of Article 2.1 of the TBT Agreement
50; and  
iii. the different tracking and verification requirements in the amended tuna measure 
accord less favourable treatment to Mexican tuna and tuna products than that 
accorded to like products from the United States and to like products originating in 
any other country, in violation of Article 2.1 of the TBT Agreement51; 
b. with respect to Mexico's claims under the GATT 1994: 
i. the eligibility criteria in the amended tuna measure accord less favourable treatment 
t o  M e x i c a n  t u n a  a n d  t u n a  p r o d u c t s  t h a n  t h a t  a c c o r d e d  t o  l i k e  p r o d u c t s  f r o m  t h e  United States and to like products originating in any other country, in violation of Articles I:1 and III:4 of the GATT 1994
52; 
ii. the different certification requirements in the amended tuna measure accord less 
favourable treatment to Mexican tuna and tuna products than that accorded to like products from the United States and to like products originating in any other country, 
in violation of Articles I:1 and III:4 of the GATT 1994
53; and 
iii. the different tracking and verification requirements in the amended tuna measure 
accord less favourable treatment to Mexican tuna and tuna products than that 
accorded to like products from the United States and to like products originating in 
any other country, in violation of Articles I:1 and III:4 of the GATT 199454; 
c. with respect to the United States' defence under Article XX(g) of the GATT 1994, the 
eligibility criteria, the different certification requirements, and the different tracking and 
verification requirements in the amended tuna measure are provisionally justified under 
Article XX(g)55; and 
d. with regard to whether the challenged aspects of the amended tuna measure satisfy the 
requirements of the chapeau of Article XX of the GATT 1994, the eligibility criteria in the 
amended tuna measure are applied in a ma nner that meets the requirements of the 
chapeau of Article XX, whereas the different certification requirements and the different 
tracking and verification requirements are applied in a manner that does not meet the 
requirements of the chapeau of Article XX of the GATT 1994.56 
                                               
48 The "eligibility criteria", the "certification requirements", and the "tracking and verification 
requirements" in the amended tuna measure are explained infra, paras. 6.8-6.14 and 7.5. 
49 Panel Report, paras. 7.135 and 8.2.a. 
50 Panel Report, paras. 7.233, 7.263, and 8.2.b. 
51 Panel Report, paras. 7.402 and 8.2.c. 
52 Panel Report, paras. 7.451, 7.499, and 8.3.a. 
53 Panel Report, paras. 7.456, 7.501, and 8.3.b. 
54 Panel Report, paras. 7.465, 7.503, and 8.3.c. 
55 Panel Report, paras. 7.541 and 8.4. 
56 Panel Report, paras. 7.585, 7.605, 7.611, and 8.5. WT/DS381/AB/RW 
 
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 1.12.  The Panel recommended, pursuant to Article 19.1 of the DSU, that the DSB request the 
United States to bring its measure into conformi ty with its obligations under the TBT Agreement 
and the GATT 1994.57 
1.13.  On 5 June 2015, the United States notified the DSB, pursuant to Articles 16.4 and 17 of the 
DSU, of its intention to appeal certain issues of law covered in the Panel Report, and certain legal 
interpretations developed by the Panel, and fi led a Notice of Appeal and an appellant's 
submission.58 On 10 June 2015, Mexico notified the DSB, pursuant to Articles 16.4 and 17 of the 
DSU, of its intention to appeal certain issues of law covered in the Panel Report, and certain legal 
interpretations developed by the Panel, and filed a Notice of Other Appeal and an other appellant's submission.
59 On 23 June 2015, Mexico and the United States each filed an appellee's 
submission.60 On 26 June 2015, Canada, the European Union, Japan, and New Zealand each filed a 
third participant's submission.61 On the same day, Australia, China, Guatemala, Korea, and 
Norway each notified its intention to appear at the oral hearing as a third participant.62 
On 17 September 2015, Thailand also notified its intention to appear at the oral hearing as a 
third participant.63 
1.14.  On 13 July 2015, the Appellate Body Division  hearing this appeal informed the participants 
and the third participants that the oral hearing would take place on 7-8 September 2015. 
On 15 July 2015, the Division received a letter from Mexico requesting that the oral hearing not be 
held as scheduled because a key member of Mexico's litigation team would not be available on those dates. Mexico submitted that attending the hearing with a reduced legal team would have an 
impact on its ability to present adequately its arguments before the Appellate Body. Mexico 
requested the Division to modify the date of the oral hearing to a date either before, or after, 
7-8 September 2015, and proposed 3-4 September or 21-22 September as possible alternative dates. The Division wrote to the United States and to the third participants soliciting their views on 
Mexico's request. Neither the United States nor any of the third participants objected to Mexico's 
request, at least with respect to the proposed alternative dates of 21-22 September 2015. On 21 July 2015, the Division issued a Procedural Ruling finding that Mexico had identified 
"exceptional circumstances", within the meaning of Rule 16(2) of the Working Procedures for 
Appellate Review
64, warranting modification of the dates for the oral hearing, and deciding to hold 
the oral hearing on 21-22 September 2015.65 In reaching its conclusion, the Division took into 
account Mexico's right to defend properly its case, as well as the high level of activity experienced 
currently by the WTO dispute settlement system, which can impair a Member's ability to engage 
effectively in multiple, parallel proceedings.66  
1.15.  By letter dated 3 August 201567, the Chair of the Appellate Body notified the Chair of the 
DSB that the Appellate Body would not be able to circulate its Report within the 60-day period 
pursuant to Article 17.5 of the DSU, or within th e 90-day period pursuant to the same provision. 
The Chair of the Appellate Body explained that th is was due to a number of factors, including the 
substantial workload of the Appellate Body, scheduling difficulties arising from overlap in the 
composition of Divisions hearing appeals concurrently pending before the Appellate Body, the rescheduling of the oral hearing in this appeal, the number and complexity of the issues raised in these and concurrent appellate proceedings, and the shortage of staff in the Appellate Body 
                                               
57 Panel Report, para. 8.6. 
58 Pursuant to Rules 20 and 21, respectively, of  the Working Procedures for Appellate Review, 
WT/AB/WP/6, 16 August 2010 (Working Procedures). 
59 Pursuant to Rule 23 of the Working Procedures. 
60 Pursuant to Rules 22 and 23(4) of the Working Procedures. 
61 Pursuant to Rule 24(1) of the Working Procedures. 
62 Pursuant to Rule 24(2) of the Working Procedures. 
63 On 17 September 2015, Thailand submitted its delegation list for the oral hearing to the 
Appellate Body Secretariat and the participants and third participants in this disput e. For purposes of this 
appeal, we have interpreted this action as a notificati on expressing Thailand's intention to attend the oral 
hearing pursuant to Rule 24(4)  of the Working Procedures. 
64 WT/AB/WP/6, 16 August 2010. 
65 The Procedural Ruling is contained in Annex D of the Addendum to this Report, 
WT/DS381/AB/RW/Add.1. 
66 The Appellate Body noted, in part icular, that at least some members of the legal teams representing 
the United States and Mexico in this appeal were also representing those Members in the arbitration 
proceedings in US – COOL (Article 22.6 – US) , and that an oral hearing in those proceedings was scheduled 
for 15-16 September 2015. 
67 WT/DS381/26. WT/DS381/AB/RW 
 
- 18 - 
 
 Secretariat. The Chair of the Appellate Body esti mated that the Report in this appeal would be 
circulated to WTO Members no later than Friday, 20 November 2015.  
1.16.  The oral hearing in this appeal was held on 21-22 September 2015. The participants and 
five of the third participants (Australia, Canada, Japan, New Zealand, and Norway) made opening 
oral statements. The participants and third part icipants responded to questions posed by the 
Members of the Appellate Body Division hearing the appeal.68 
2  ARGUMENTS OF THE PARTICIPANTS 
2.1.  The claims and arguments of the participan ts are reflected in the executive summaries of 
their written submissions provided to the Appellate Body.69 The Notices of Appeal and 
Other Appeal, and the executive summaries of the participants' claims and arguments, are contained in Annexes A and B of the Addendum to this Report, WT/DS381/AB/RW/Add.1. 
3  ARGUMENTS OF THE THIRD PARTICIPANTS 
3.1.  The arguments of those third participants th at submitted written submissions are reflected in 
the executive summaries of their written submissions provided to the Appellate Body
70, and are 
contained in Annex C of the Addendum to this Report, WT/DS381/AB/RW/Add.1. 
4  ISSUES RAISED IN THIS APPEAL 4.1.  The following issues are raised in this appeal: 
a. whether the Panel erred in its application of Article 2.1 of the TBT Agreement and 
Articles I:1, III:4, and XX of the GATT 1994 by  making discrete findings regarding each 
of the three different sets of requir ements under the amended tuna measure
71, rather 
than making findings under those provisions in respect of the amended tuna measure as 
a whole (raised by Mexico); 
b. with respect to Article 2.1 of the TBT Agreement: 
i. with respect to the detrimental impact of the amended tuna measure, whether the 
Panel erred by finding that the different certification requirements and the different 
tracking and verification requirements modify the conditions of competition to the detriment of Mexican tuna products in the US market on the basis that such 
requirements impose a lesser burden on tuna products derived from tuna caught 
outside the ETP large purse-seine fishery than on tuna products derived from tuna caught within that fishery (raised by the United States); 
ii. with respect to the Panel's analysis of whether the detrimental impact of the 
amended tuna measure stems exclusively from  a legitimate regulatory distinction: 
- whether the Panel erred in its interpretation of Article 2.1 by articulating an 
incorrect legal standard (raised by the United States); 
- with respect to the "eligibility criteria" (raised by Mexico): 
                                               
68 On 29 June 2015, the Appellate Body received one unsolicited amicus curiae  brief from a professor of 
law. The Division hearing this appeal did not find it necessary to rely on this amicus curiae  brief in rendering its 
decision. 
69 Pursuant to the Appellate Body's communication on "Executive Summaries of Written Submissions in 
Appellate Proceedings" and "Guidelines in Respect of Executive Summaries of Written Submissions in Appellate 
Proceedings". (WT/AB/23, 11 March 2015) 
70 Pursuant to the Appellate Body's communication on "Executive Summaries of Written Submissions in 
Appellate Proceedings" and "Guidelines in Respect of Executive Summaries of Written Submissions in Appellate 
Proceedings". (WT/AB/23, 11 March 2015) 
71 The three different sets of requirements – the "eligi bility criteria", the "certification requirements", 
and the "tracking and verificati on requirements" – in the amended tuna measure are explained infra, 
paras. 6.8-6.14 and 7.5.  WT/DS381/AB/RW 
 
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  whether the Panel erred in its application of Article 2.1 by misreading the 
Appellate Body's findings in the original proceedings; and 
 whether the Panel acted inconsistently with its duty to conduct an objective 
assessment of the matter pursuant to Article 11 of the DSU in reaching its 
findings: (i) regarding the unobserved adverse effects on dolphins of the 
fishing method of "setting on" dolphins; (ii) regarding the unobserved adverse effects on dolphins of tuna fishing methods other than setting on 
dolphins; and (iii) that the Appellate Body had made a finding in the 
original proceedings that setting on dolphins is more harmful to dolphins than other fishing methods; and 
- with respect to the "certification requirements" and the "tracking and 
verification requirements": 
 whether the Panel erred in its application of Article 2.1 by not taking into 
account: (i) the different levels of risk to dolphins inside and outside the 
ETP large purse-seine fishery; or (ii) the fact that the certification 
requirements and the tracking and verification requirements that apply to the ETP large purse-seine fishery reflect international obligations under 
the AIDCP (raised by the United States);  
 whether the Panel disregarded evidence on the record and thereby acted 
inconsistently with its duty to conduct an objective assessment of the matter pursuant to Article 11 of the DSU by failing to find that: (i) captains 
in some cases have an economic incentive to under-report dolphin injury 
and mortality; and (ii) tuna-dolphin association and setting on dolphins occur in certain ocean regions outside the ETP (raised by Mexico); and 
 whether, with respect to the "determination provisions"
72 (raised by the 
United States): 
o  the Panel erred in its application of Article 2.1 by: (i) improperly making 
the case for Mexico; and (ii) making its findings based solely on the 
design of the determination provisions and not on their application; 
o  the Panel acted inconsistently with its duty to conduct an objective 
assessment of the matter pursuant to Article 11 of the DSU by failing to 
base its findings on a sufficient evidentiary basis; and 
c. whether the Panel erred in its application of Article I:1 of the GATT 1994 to the amended 
tuna measure by finding that the certification requirements and the tracking and 
verification requirements under the amen ded tuna measure provide an "advantage, 
favour, privilege, or immunity" to tuna products from other Members that is not "accorded immediately and unconditionally" to like products from Mexico because they 
impose a lesser burden on tuna products derived from tuna caught outside the ETP large 
purse-seine fishery than on tuna products derived from tuna caught within that fishery (raised by the United States); 
d. whether the Panel erred in its application of Article III:4 of the GATT 1994 to the 
amended tuna measure by finding that the certification requirements and the tracking 
and verification requirements under the amended tuna measure accord "treatment less favourable" to Mexican tuna products than that accorded to like domestic products 
because they impose a lesser burden on tuna products derived from tuna caught outside 
the ETP large purse-seine fishery than on tuna products derived from tuna caught within that fishery (raised by the United States); and 
                                               
72 The "determination provisions" in the amended tuna measure are explained infra, para. 6.11. WT/DS381/AB/RW 
 
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 e. with respect to the chapeau of Article XX of the GATT 1994: 
i. whether, in assessing "countries where the same conditions prevail", the Panel erred 
in its application of the chapeau of Article XX by finding that:  
- the conditions are not the same in respect of the eligibility criteria (raised by 
Mexico); or  
- the conditions are the same in respect of  the certification requirements and the 
tracking and verification requirements (raised by the United States); 
ii. whether, in assessing "arbitrary or unjustifiable discrimination": 
- the Panel erred in its interpretation of the chapeau of Article XX by articulating 
an incorrect legal standard and improperly relying on its analysis under Article 2.1 of the TBT Agreement (raised by the United States);  
- the Panel erred in its application of the chapeau of Article XX by finding that the 
eligibility criteria are not applied in a manner that constitutes a means of arbitrary or unjustifiable discrimination (raised by Mexico);  
- the Panel erred in its application of the chapeau of Article XX by finding that the 
certification requirements and the tracking and verification requirements are applied in a manner that constitutes a means of arbitrary or unjustifiable 
discrimination and, more specifically, whether the Panel erred (raised by the 
United States): 
 by not taking into account the different levels of risk to dolphins inside and 
outside the ETP large purse-seine fishery;  
 by not taking into account the fact that the certification requirements and 
the tracking and verification requirements that apply to the ETP large purse-seine fishery reflect international obligations under the AIDCP; and  
 in finding that, due to the determination provisions, the certification 
requirements constitute a means of arbitrary and unjustifiable discrimination. 
5  PRELIMINARY ISSUES 
5.1  Business confidential information 5.1.  The cover page of Mexico's appellee's submission indicates that it "[c]ontains business 
confidential information (BCI) on page 13".
73 Mexico also indicates in the cover letter to its 
appellee's submission that it has served a "non-BCI version" of that submission on the 
third participants.  
5.2.  Neither participant has requested that we adopt special procedures for handling information 
designated as BCI in these appellate proceedings, although the European Union, in its 
third participant's submission, requests that the issue of BCI be addressed in this Report. The 
European Union does not, however, refer to Mexico's appellee's submission. Rather, the 
European Union asserts that, in these proceedings, its ability to comment upon the Panel Report is 
                                               
73 On page 13 of that submission, two sentences of paragraph 29, and four sent ences of footnote 50 to 
paragraph 29 are enclosed within double square br ackets, indicating that these sentences are BCI. WT/DS381/AB/RW 
 
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 impaired by the extensive redaction of text said to contain BCI from the Panel's reasoning with 
respect to the tracking and verification re quirements under the amended tuna measure.74 
5.3.  In disputes raising issues relating to BCI, the Appellate Body has highlighted the need to 
distinguish between "the general layer of confidentiality that applies in WTO dispute settlement 
proceedings, as foreseen in Articles 18.2 and 13.1 of the DSU", and "the additional layer of 
protection of sensitive business information that a panel may choose to adopt, usually at the request of a party".
75 It is for the parties to request and justify the need for additional protection 
of BCI.76 It is for the panel and/or the Appellate Body, relying upon objective criteria, to determine 
whether particular information deserves additional  protection, as well as the degree of protection 
that is warranted.77 When additional procedures to protect BCI are adopted, the panel and/or 
Appellate Body must also "adjudicate any disagreement or dispute that may arise under those 
procedures regarding the designation or the trea tment of information as business confidential".78 It 
is, moreover, for the adjudicator to ensure that an  appropriate balance is struck between the need 
to guard against the risk of harm that could resu lt from the disclosure of particularly sensitive 
information, on the one hand, and the integrity of the adjudication process, the participation rights 
of third participants, and the rights and systemic interests of the WTO membership at large, on the other hand.
79 That same balance must be struck by a panel in applying any additional procedures 
adopted. This means, among other things, that, when considering whether to redact information 
from its report, a panel "should bear in mind the rights of third parties and other WTO Members under various provisions of the DSU"
80 and "ensure that the public version of its report circulated 
to all Members of the WTO is understandable."81  
5.4.  In these proceedings, while the cover page of the Panel Report does not mention BCI, the 
Panel redacted, in part or in full, 17 paragraphs and 3 footnotes of its Report, in each case replacing the redacted text with the following designation: " [[BCI]] ".
82 We see no indication in 
the Panel record suggesting that either Mexico or the United States requested the adoption of 
special procedures to protect BCI. Nor does the record show that the Panel adopted such special 
procedures either as part of its Working Procedures or on an ad hoc  basis.83 The Panel Report also 
lacks an indication of the criteria used to identify the information considered to constitute BCI. We 
are therefore surprised by the fact that the Pane l redacted portions of its reasoning from its 
Report, and uncertain of the legal basis on which it did so.  
                                               
74 The European Union contends that its ability to comment on the Panel's analysis of the tracking and 
verification requiremen ts is "hampered" by the Pa nel Report circulated to Members, which "contains many 
instances in which allegedly confidential information has been extensively deleted". The European Union notes that some of this information was described by the Pa nel as "crucial" to its assessment. (European Union's 
third participant's submission, para. 52 (quoting Panel Report, para. 7.561)) The Eu ropean Union remarks that 
its ability to participate as a third participant has been si gnificantly curtailed, and, re ferring to Article 18.2 of 
the DSU, considers that "the Panel Report should have contained an indication of the extent of the redactions and a non-confidential summary of the re dacted information." (Ibid., para. 52)  
75 Appellate Body Reports, China – HP-SSST (Japan)/China – HP-SSST (EU) , para. 5.315. 
76 In EC and certain member States – Large Civil Aircraft , the Appellate Body explained that the "burden 
of justification will increase the more the proposed arra ngements affect the exercise by the Appellate Body of 
its adjudicative duties, the exercise by the participants of their rights to due process and to have the dispute 
adjudicated, the exercise by the thir d participants of their participatory rights, and the rights and systemic 
interests of the WTO membership at  large." (Appellate Body Report, EC and certain member States – Large 
Civil Aircraft , Annex III, Procedural Ruling of 10 August 2010,  para. 10. See also Appellate Body Reports, 
China – HP-SSST (Japan)/China – HP-SSST (EU) , para. 5.311) 
77 Appellate Body Report, EC and certain member States – Large Civil Aircraft , Annex III, Procedural 
Ruling of 10 August 2010, para. 15. 
78 Appellate Body Reports, China – HP-SSST (Japan)/China – HP-SSST (EU) , para. 5.311. 
79 Appellate Body Report, EC and certain member States – Large Civil Aircraft , Annex III, Procedural 
Ruling of 10 August 2010, para. 15. 
80 For example, Articles 12.7 and 16 of the DSU. See Appellate Body Report, Japan – DRAMS (Korea) , 
para. 279. 
81 Appellate Body Report, Japan – DRAMS (Korea) , para. 279. 
82 See Panel Report, paras. 6.15-6.16, 6.18, 7.309-7.311, 7.319-7.322, 7.356-7.359, 7.361-7.362, 
and 7.370, and fns 79, 515, and 579 thereto. We note th at the Panel record that was transmitted to the 
Appellate Body contains a version of  the Panel Report that states " [BCI VERSION] " on its cover page; carries 
the symbol "WT/DS381/BCI/RW" on each page; and in cludes all the text that was redacted from the 
Panel Report circulated to Members on 14 April 2015, which carries the symbol "WT/DS381/RW" on each page. 
83 The participants confirmed our understanding in this regard in response  to questioning at the 
oral hearing. WT/DS381/AB/RW 
 
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 5.5.  We also observe that, absent any request from the participants, procedures for additional 
protection of BCI do not apply in these appellate proceedings.  
5.2  The scope of Article 21.5 proceedings 5.6.  A second preliminary issue relates to the scope of these proceedings under Article 21.5 of the 
DSU. We note that neither Mexico nor the United States claims on appeal that the Panel erred in 
interpreting Article 21.5, or in understanding th e scope and nature of proceedings conducted under 
that provision.
84 Nonetheless, we find it useful to recall certain observations that the 
Appellate Body has previously made in this regard. 
5.7.  The task of a panel operating pursuant to Article 21.5 of the DSU is to resolve disagreements 
"as to the existence or consistency with a covered agreement of a measure taken to comply with the recommendations and rulings" of the DSB.
85 Article 21.5 proceedings involve "a new and 
different measure which was not before the original panel"86, such that "the claims, arguments and 
factual circumstances which are pertinent to the 'measure taken to comply' will not, necessarily, be the same as those which were pertinent in the original dispute."
87 When a Member revises a 
measure found to be WTO-inconsistent in the original proceedings by modifying only certain 
aspects and leaving others unchanged, such revision, in principle, turns the original measure "in its totality"
88 into a "new and different measure".89 Indeed, even when certain elements of a 
compliance measure remain unchanged from an original measure, the legal import and 
significance of such elements may be altered as a result of the modifications introduced in other 
parts of the compliance measure.90 
5.8.  In reviewing the WTO-consistency of a measure "taken to comply", compliance panels should 
be mindful of the principle of prompt settlement of disputes embodied in Article 3.3 of the DSU.91 
Accordingly, compliance proceedings cannot be used "to 're-open' issues decided in substance in 
                                               
84 However, the United States did argue before the Panel that the 2013 Final Rule is the sole instrument 
constituting the "measure taken to comply" with the recommendations and rulings of the DSB, and that the Panel should limit the scope of its review to this le gal instrument. (Panel Report , para. 7.17 (referring to 
United States' first written submission to the Panel, para. 13; and second written submission to the Panel, 
para. 4)) The United States further argued that the three elements of the amended tuna measure on which Mexico based its claims – i.e. the eligibility criteria, the certification requirements, and the tracking and verification requirements – are all unchanged from the original measure, and that therefore Mexico could not 
raise claims relating to these elements in these compliance proceedings. (Ibid., para. 7.27) The Panel rejected the United States' arguments. It reasoned, inter alia , that a compliance measure is, in principle, a "new and 
different measure" even when it co ntains aspects that remain unchange d from the original measure. (Ibid., 
para. 7.39 (quoting Appe llate Body Reports, US – Zeroing (EC) (Article 21.5 – EC) , para. 432; and  
Canada – Aircraft (Article 21.5 – Brazil) , para. 36)) Thus, the Panel stated that its mandate was to examine 
"whether the amended tuna measure, including  the 2013 Final Rule, brings the United States into compliance" 
with the WTO Agreement. (Ibid., pa ras. 7.24 and 7.43 (emphasis added)) 
85 Appellate Body Report, US – Softwood Lumber VI (Article 21.5 – Canada) , para. 102. See also Panel 
Report, EC – Fasteners (China) (Article 21.5 – China) , paras. 7.22-7.23. 
86 Appellate Body Report, Canada – Aircraft (A rticle 21.5 – Brazil) , para. 41. 
87 Appellate Body Report, Canada – Aircraft (A rticle 21.5 – Brazil) , para. 41. 
88 Appellate Body Report, US – Shrimp (Article 21.5 – Malaysia) , para. 87. 
89 Appellate Body Reports, US – Zeroing (EC) (Article 21.5 – EC) , para. 432; Canada – Aircraft 
(Article 21.5 – Brazil) , para. 41. 
90 See Appellate Body Report, EC – Bed Linen (Article 21.5 – India) , fn 101 to para. 86. The 
Appellate Body reasoned that a change  in one element of the anti-dumping determination made to comply with 
the DSB's recommendations and rulings – i.e. the volume  of "dumped imports" – ma y affect another element 
of that determination that remained unchanged from the original measure – i.e. the injury caused by "other 
factors". 
91 Appellate Body Report, EC – Bed Linen (Article 21.5 – India) , para. 94. See also Appellate Body 
Reports, US – Shrimp (Article 21.5 – Malaysia) , para. 97; and Chile – Price Band System (Article 21.5 – 
Argentina) , para. 236. WT/DS381/AB/RW 
 
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 the original proceedings".92 At the same time, if certain claims  against aspects of a measure were 
not decided on the merits in the original proceedings, "they are not covered by the recommendations and rulings of the DSB" and, ther efore, "a Member should not be entitled to 
assume that those aspects of the measure are consistent with the covered agreements."
93 In  
US – Upland Cotton (Article 21.5 – Brazil) , the Appellate Body stated that "[a] complaining 
Member ordinarily would not be allowed to raise claims in an Article 21.5 proceeding that it could have pursued in the original proceedings, but did not."
94 In US – Zeroing (EC) (Article 21.5 – EC) , 
the Appellate Body clarified, however, that this is not the case for "new claims against a measure 
taken to comply" when such measure "incorporates components of the original measure that are unchanged, but are not separable from other aspects of the measure taken to comply".
95 Thus, the 
possibility to challenge an element of the measure at issue for the first time in compliance 
proceedings, even if that element may not have changed, hinges on the "critical question" of 
whether such an element forms "an integral part of the measure taken to comply".96 
5.9.  The Appellate Body has also explained that "Article 21.5 proceedings do not occur in isolation 
from the original proceedings, but that both pr oceedings form part of a continuum of events."97 
Since Article 21.5 of the DSU expressly links the "measures taken to comply" with the recommendations and rulings of the DSB concerning the original measure, a panel's examination 
of a measure taken to comply "cannot … be undertaken in abstraction from the findings by the 
original panel and the Appellate Body adopted by the DSB"
98, but must rather be conducted "with 
due cognizance of this background".99 Indeed, "doubts could arise about the objective nature of an 
Article 21.5 panel's assessment" if, on a specific issue, that panel were to "deviate from the 
reasoning" in the original report "in the absence of any change in the underlying evidence in the 
record".100 In other words, a compliance panel should take due account of the relevant reasoning 
that led to the original measure being found to be WTO-inconsistent in its examination of whether 
the measure taken to comply redresses such WTO-inconsistencies. The relevance of the original 
reasoning and findings to a compliance panel's analysis must be ascertained on a case-by-case basis, and may vary depending on factors such as the degree of similarity between the measure 
taken to comply with the original measure, or the extent to which the features of the relevant 
market have changed. 
                                               
92 Panel Reports, US – COOL (Article 21.5 – Canada and Mexico) , para. 7.47 (quoting Appellate Body 
Report, US – Zeroing (EC) , para. 427; and referring to Appellate Body Report, EC – Bed Linen (Article 21.5 – 
India) , paras. 96-98). Thus, for instance, a co mplainant that failed to make out a prima facie  case in the 
original proceedings regarding an element of the me asure that remained unchanged since the original 
proceedings "may not re-litigate the same claim with respect to the unchanged element of the measure in the Article 21.5 proceedings." (Appellate Body Report, US – Upland Cotton (Article 21.5 – Brazil) , para. 210 
(referring to Appellate Body Report, EC – Bed Linen (Article 21.5 – India) , para. 93)) Similarly, "a complainant 
may not reassert the same claim against an unchanged aspect of the measure that had been found to be 
WTO-consistent  in the original proceeding s." (Appellate Body Report, US – Upland Cotton (Article 21.5 – 
Brazil) , para. 210 (referring to Appellate Body Report, US – Shrimp (Article 21.5 – Malaysia) , para. 96) 
(emphasis original)) 
93 Appellate Body Report, US – Zeroing (EC) (Article 21.5 – EC) , para. 424. 
94 Appellate Body Report, US – Upland Cotton (Article 21.5 – Brazil) , para. 211. 
95 Appellate Body Report, US – Zeroing (EC) (Article 21.5 – EC) , para. 432. 
96 Appellate Body Report, US – Zeroing (EC) (Article 21.5 – EC) , para. 434. See also Panel Report,  
EC – Fasteners (China) (Article 21.5 – China) , para. 7.65. 
97 Appellate Body Report, Chile – Price Band System (Article 21.5 – Argentina) , para. 136 (referring to 
Appellate Body Report, Mexico – Corn Syrup (Article 21.5 – US) , para. 121). See also Appellate Body Report, 
US – Upland Cotton (Article 21.5 – Brazil) , para. 386. 
98 Appellate Body Report, Chile – Price Band System (Article 21.5 – Argentina) , para. 136 (referring to 
Appellate Body Reports, US – Softwood Lumber VI (Article 21.5 – Canada) , para. 102; and US – Softwood 
Lumber IV (Article 21.5 – Canada) , para. 77). 
99 Appellate Body Report, Chile – Price Band System (Article 21.5 – Argentina) , para. 136 (referring to 
Appellate Body Report, Mexico – Corn Syrup (Article 21.5 – US) , para. 121). 
100 Appellate Body Report, US – Softwood Lumber VI (Article 21.5 – Canada) , para. 103. See also 
Appellate Body Report, US – Upland Cotton (Article 21.5 – Brazil) , para. 386. WT/DS381/AB/RW 
 
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 6  BACKGROUND AND OVERVIEW OF THE MEASURE AT ISSUE 
6.1.  These proceedings under Article 21.5 of the DSU concern a labelling regime for tuna 
products101 maintained by the United States. 
6.2.  Commercial tuna fishing can have harmful effects on marine mammals, including dolphins, 
and these may vary depending on factors such as the method of fishing used, the size of the 
fishing vessel, and the area of the ocean in which the vessel engages in tuna fishing. Since the 1970s
102, the United States has undertaken certain domestic measures, and participated in 
certain multilateral initiatives, aimed at reducing the adverse effects on dolphins associated with 
commercial fishing operations.  
6.3.  In 1990, the United States put in place a domestic regime for labelling tuna products as 
"dolphin-safe" through the enactment of the DPCIA.103 As explained below, this instrument, as 
subsequently amended, together with its implemen ting regulations and a court decision, constitute 
the "amended tuna measure", the measure at issue in these compliance proceedings. Together, these instruments aim to: (i) ensure that consumers are not misled or deceived about whether 
tuna products contain tuna caught in a manner that adversely affects dolphins; and (ii) contribute 
to the protection of dolphins by ensuring that the US market is not used to encourage fishing fleets to catch tuna in a manner that adversely affects dolphins.
104 The amended tuna measure defines 
what constitutes dolphin-safe tuna products for purposes of the US market, and establishes certain 
requirements and conditions that must be satisfied in order for a tuna product sold in the United States to bear a label indicating that it  is dolphin-safe. The preferences of consumers and 
retailers in the United States are such that a dolphin-safe label has "significant commercial value" 
in the US market for tuna products.
105 
6.4.  At the international level, both the United States and Mexico are parties to the AIDCP, an 
agreement among 14 countries that entered into force in February 1999.106 The AIDCP, 
administered by the Inter-American Tropical T una Commission (IATTC), addresses a particular 
tuna fishing method (purse-seine fishing) in a specific area of the ocean, namely, the Eastern Tropical Pacific Ocean (ETP).
107  
                                               
101 The DPCIA defines "tuna product" in Section 1385( c)(5) as a "food item which contains tuna and 
which has been processed for retail sale, except perishab le sandwiches, salads, or other products with a shelf 
life of less than 3 days". In addition, for purposes of CFR Title 50, Section 216, "tuna product" means "any food 
product processed for retail sale and intended for human or animal consumption" containing one of the species 
of tuna listed in CFR Title 50, Section 216.24(f)(2)(i) and (ii), and not including "perishable items with a shelf life of less than 3 days". (Original Panel Report, paras. 7.60-7.61) 
102 In the original proceedings, Mexico commented that "[t]he principal US law relating to the overall 
issue of the protection of dolphins and other marine mammals is the Marine Mammal Protection Act of 1972, as amended (the 'MMPA')". (Origi nal Panel Report, para. 4.17) 
103 Aspects of the MMPA and the DPCIA were challe nged by Mexico and the European Economic 
Communities in disputes brought under the General Agreement on Tariffs and Trade 1947, but the panel 
reports in those disputes were never adop ted. These reports are GATT Panel Reports, US – Tuna (Mexico) ; and 
US – Tuna (EEC) . 
104 Panel Report, para. 7.523. See also Appellate Body Report,  US – Tuna II (Mexico) , para. 302; and 
Original Panel Report, paras. 7.401 and 7.425. 
105 Appellate Body Report, US – Tuna II (Mexico) , para. 233 (referring to Original Panel Report, 
paras. 7.289-7.290). Following public campaigning by the environmental organization Earth Island Institute in 
the late 1980s, tuna processors responded to pressure to stop purchasing tuna caught in conditions that were harmful to dolphins. (Original Panel Report, para. 7.288) 
106 Belize, Colombia, Costa Rica, Ecuador, El Salv ador, the European Union, Guatemala, Honduras, 
Mexico, Nicaragua, Panama, Peru, the United States, and Venezuela are parties to the AIDCP. Bolivia and 
Vanuatu apply the AIDCP provisionally. (See United States' appellant's submis sion, fn 47 to para. 60) 
107 Original Panel Report, para. 2.35. In 1976, the IATTC  began multilateral endeavours that led to the 
creation of the International Dolphin Conservation Program (IDCP). The effo rts were reflected in a series of 
multilateral agreements. These agreements were the La  Jolla Agreement (1992) and the Panama Declaration 
(1995), which were succeeded by the AIDCP (1999). (Ibid.) WT/DS381/AB/RW 
 
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 6.5.  Within this area of the ocean108, there is a regular association between tuna and dolphins, 
meaning that schools of tuna tend to aggregate and swim beneath certain species of dolphins.109 
Certain vessels operating in this area thus employ the fishing technique known as "setting on" dolphins, which takes advantage of this association, and involves chasing and encircling the 
dolphins with a purse-seine net in order to catch the tuna swimming beneath the dolphins.
110 The 
ETP is a "traditional fishing ground" for Mexico, and its tuna fleet operates almost exclusively therein using the method of setting on dolphins.
111 
6.6.  The AIDCP was negotiated in response to ev idence that many dolphins were dying in the ETP 
each year112 and, together with the instruments that have been adopted thereunder113, establishes 
a programme of monitoring, tracking, verification, and certification of particular tuna fishing practices in the ETP.
114 The AIDCP is recognized to have made an important contribution to dolphin 
protection and to the dramatic reduction of observed dolphin mortality in the ETP.115 The AIDCP 
regulates the fishing methods of purse-seine vessels in the ETP according to the size of the vessel, by prohibiting small purse-seine vessels from setting on dolphins and permitting large purse-seine 
vessels to set on dolphins only within specified dolphin mortality limits (DMLs).
116 Under the 
AIDCP, large purse-seine vessels are also subject to a number of requirements in respect of the 
fishing gear that they must carry and certain procedures that they must perform, so as to reduce 
the risks to dolphins arising from setting on dolphins. The AIDCP has established certain 
mechanisms to enforce these requirements and mo rtality limits. In addition to mandating the 
presence of independent observers on board larg e purse-seine vessels fishing in the ETP, each 
party must also establish its own tracking and verification programme, implemented and operated 
by a designated national authority, and ensure that  it includes periodic audits and spot checks for 
tuna products.117 Finally, voluntary procedures are put in place to enable tuna caught and tracked 
in accordance with this programme to receive an "AIDCP dolphin-safe certification".118 As 
                                               
108 The ETP, as defined under US law, extends westwa rd from the west coast of the Americas to include 
most of the tropical Pacific east of the Hawaiian Islands,  and includes high seas areas as well as the exclusive 
economic zones and territorial seas of Chile, Colombia, Costa Rica, Ecuador, El Salvador, France (due to the 
French overseas possession, Clipperton Island), Guat emala, Honduras, Mexico, Nicaragua, Panama, Peru, and 
the United States. More specifically, the DPCIA defines the ETP as "the area of the Pacific Ocean bounded by 
40 degrees north latitude, 40 degrees south latitude, 160 degrees west longitude, and the western coastlines of North, Central, and South Am erica". (Appellate Body Report, US – Tuna II (Mexico) , fn 356 to para. 172 
(quoting Section 1385(c)(2) of the DPCIA)) 
109 Original Panel Report, paras. 4.6 and 7.306; Appellate Body Report, US – Tuna II (Mexico) , fn 355 to 
para. 172.  
110 Appellate Body Report, US – Tuna II (Mexico) , fn 355 to para. 172. The original panel found that 
setting on dolphins occurs especially  in the ETP because of the regular association observed between tuna and 
dolphins in that area. (Original Panel Report,  para. 7.306. See also Appellate Body Report, US – Tuna II 
(Mexico) , para. 248) 
111 Appellate Body Report, US – Tuna II (Mexico) , para. 234. See also Original Panel Report, para. 7.308 
(referring to Mexico's first written submission to the original panel, paras. 165, 167, 186, and 188). 
112 Original Panel Report, para. 2.35. 
113 In particular, AIDCP, Resolution to Adopt the Modi fied System for Tracking and Verification of Tuna 
(AIDCP Tracking and Verification System) (Original Panel Exhibit MEX-55; Panel Exhibit MEX-36) (see Panel 
Report, para. 7.296; and Original Panel Report, para. 2.40) ; and AIDCP, Resolution to Establish Procedures for 
AIDCP Dolphin Safe Tuna Certification (Original Panel Exhibit MEX-56; Panel Exhibit MEX-115) (see Original 
Panel Report, para. 2.41). Both resolutions were adop ted by the parties to the AIDCP on 20 June 2001. 
114 Original Panel Report, para. 2.39. The objectiv es of the AIDCP are threefold: (i) to reduce 
progressively incidental dolphin mortalities in the tuna  purse-seine fishery in the Agreement Area to levels 
approaching zero, through the setting of annual limits; (ii)  with the goal of eliminating dolphin mortality in this 
fishery, to seek ecologically sound means of capturing large yellowfin tunas not in association with dolphins; and (iii) to ensure the long-term sustainability of the tu na stocks in the Agreement Area, as well as that of the 
marine resources related to this fishery, taking into consideration the interrelationship among species in the ecosystem, with special emphasis on, inter alia , avoiding, reducing, and minimi zing bycatch and discards of 
juvenile tuna and non-target specie s. (Article II of the AIDCP (Origina l Panel Exhibits US-23a and MEX-11; 
Panel Exhibit MEX-30)) 
115 Original Panel Report, paras. 2.39 and 7.609. 
116 Large purse-seine vessels are defi ned as vessels with a carrying capacity greater than 363 metric 
tons. The AIDCP does not apply to other fishing vessels in the ETP, such as longline vessels, and pole and line 
vessels. According to the United States, this is because such vessels are not capable of setting on dolphins. (United States' appellant's submission, fn 61 to para. 65; Annexes I,  IV(I)(3)(c), and VII(6) to the AIDCP 
(Original Panel Exhibits US-23a and MEX-11; Panel Exhibit MEX-30)) 
117 Original Panel Report, para. 7.611. 
118 Original Panel Report, para. 2.41; Article 2.1 of the AIDCP Dolphin Safe Certification Resolution 
(Original Panel Exhibit MEX-56; Panel Exhibit MEX-115). WT/DS381/AB/RW 
 
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 discussed below, the AIDCP's definition of "dolphin safe" is not coextensive with the definition of 
"dolphin safe" under the US measure at issue in this dispute.119  
6.1  The amended tuna measure 6.7.  Mexico challenges the United States' regulatory regime establishing the conditions for the use 
of a dolphin-safe label on tuna products sold in the US market. As discussed above
120, in its 
request for the establishment of an Article 21.5 panel, Mexico asserted that the US regime comprises the following three legal instruments: (i) the DPCIA
121; (ii) the implementing 
regulations122; and (iii) the Hogarth ruling.123 
6.8.  Taken together, the DPCIA, the implementing  regulations, and the Hogarth ruling constitute 
the "amended tuna measure"124 and condition access to a dolphin-safe label upon certain 
requirements that vary depending on the fishing method by which tuna contained in the tuna 
product is harvested, the ocean area where it is  caught, and the type of vessel used. The DPCIA 
and the implementing regulations also prohibit any reference to dolphins, porpoises, or marine mammals on the label of a tuna product if the tuna contained in the product does not comply with 
the labelling conditions spelled out in these instruments.
125  
6.9.  The amended tuna measure sets out several substantive conditions for access to the 
dolphin-safe label. First, the measure disqualifies from access to that label all tuna products 
containing tuna harvested by two methods of fishing: (i) large-scale driftnet fishing on the high 
s e a s ;  a n d  ( i i )  v e s s e l s  u s i n g  p u r s e - s e i n e  n e t s  t o  e n c i r c l e  o r  " s e t  o n "  d o l p h i n s  a n y w h e r e  i n  t h e  world.
126 Although the DPCIA's disqualification of tuna products derived from tuna caught by 
setting on dolphins was suspended in 2002 by virtue of administrative action127, the Hogarth ruling 
overturned that action shortly thereafter128, thereby restoring this condition of access to the 
US dolphin-safe labelling regime. The disqualification of tuna products containing tuna caught by setting on dolphins thus formed part of, and is unchanged as compared to, the original tuna 
measure. Second, all other tuna products, that is, those containing tuna harvested by all other 
fishing methods, are eligible for the dolphin-safe label only if no dolphins were killed or seriously injured in the sets or other gear deployment in which the tuna were caught. The amended tuna 
                                               
119 Under the AIDCP Dolphin Safe Certification Resolution, "dolphin-safe tuna" is defined as "tuna 
captured in sets in which there is no mortality or seri ous injury of dolphins", and "non-dolphin-safe tuna" is 
defined as "tuna captured in sets in  which mortality or serious injury of  dolphins occurs". (Original Panel 
Report, para. 2.40) 
120 See supra , para. 1.9. 
121 Original Panel Exhibit US-5; Panel Exhibit MEX-8. 
122 Panel Exhibit US-2. 
123 Original Panel Exhibit MEX-31; Panel Exhibit MEX- 16. Mexico further challe nged any implementing 
guidance, directives, policy announcements or any other document issued in relation to instruments (i) through (iii), including any modifications or amendmen ts in relation to those in struments. (Panel Report, 
para. 2.1 (referring to Mexico's panel request; and first written submission to the Panel, para. 11)) 
124 The US dolphin-safe labelling provisions do not make the use of a dolphin-safe label obligatory for 
the importation or sale of tuna products in the United States. (Appellate Body Report, US – Tuna II (Mexico) , 
para. 196) 
125 Section 1385(d)(3)(B) of the DPCIA; Section 216.90 of the implementing regulations. See also 
Appellate Body Report, US – Tuna II (Mexico) , para. 172. 
126 Panel Report, paras. 3.35-3. 36; Appellate Body Report, US – Tuna II (Mexico) , para. 174. 
127 According to Section 1385(h) of the DPCIA, the type of certification required for tuna products 
containing tuna harvested by large purse-seine vessels in  the ETP was subject to a finding by the US Secretary 
of Commerce on whether the intentional deployment on or  encirclement of dolphins with purse-seine nets was 
having a significant adverse impact on any depleted dolphin stock in the ETP. The US Secretary of Commerce initially found that setting on dolphins was not having a significant adverse effect on  any depleted dolphin stock 
in the ETP. The effect of this findin g was that tuna products containing tuna caught by setting on dolphins 
could be labelled dolphin-safe provided that the other cond itions for access to the label were satisfied. (Original 
Panel Report, para. 2.18; Appellate Body Report, US – Tuna II (Mexico) , para. 176) 
128 The finding of the US Secretar y of Commerce was overruled in Earth Island Institute v. Evans , on the 
basis that the Secretary failed to conduct statutorily ma ndated studies and that the best available scientific 
evidence did not support the Secretary's finding. The ruli ng was affirmed on appeal in the Hogarth ruling. As a 
result, Section 1385(h) requires that tuna products derived from tuna harvested by large purse-seine vessels in the ETP may be labelled dolphin safe only if the ca ptain and an IDCP-approved observer certify both that 
there was "no setting on dolphins" and that there were "n o dolphins killed or seriously injured". (Panel Report, 
para. 3.19. See also Original Panel Report, paras. 2.15-2.20; and A ppellate Body Report, US – Tuna II 
(Mexico) , paras. 175-176) WT/DS381/AB/RW 
 
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 measure also prescribes a number of certification requirements and tracking and verification 
requirements relating to the substantive conditions.  
6.10.  Apart from large-scale driftnet fishing on the high seas129, the amended tuna measure 
distinguishes among three general categories of fisheries130: (i) large purse-seine131 vessels in the 
ETP132 (the ETP large purse-seine fishery); (ii) purse-seine vessels outside the ETP133 (the non-ETP 
purse-seine fishery); and (iii) other fisheries, which include non-purse-seine vessels in any ocean area and small purse-seine vessels in the ETP ("all other fisheries").
134 Access to the dolphin-safe 
label for all fisheries requires certification that no dolphins were killed or seriously injured in the 
sets or other gear deployment in which the tuna were caught ("no dolphins killed or seriously 
injured" certification). For tuna caught by purse-seine vessels falling within the first two categories, certification that no purse-seine net was intentionally deployed on or used to encircle 
dolphins during the particular trip on which the tuna were caught ("no setting on dolphins" 
certification) is also a condition of access to the label. The relevant certification(s) must be made by a vessel's captain. The relevant certification(s) may also need to be made by an observer in 
certain defined circumstances. 
6.11.  More specifically, for tuna products derive d from tuna caught in the ETP large purse-seine 
fishery, both of the above certifications have to be provided by both the captain and an 
International Dolphin Conservation Program (IDCP )-approved observer. For tuna products derived 
from tuna caught in any fishery other than the ETP large purse-seine fishery, these certifications have to be provided, in principle, only by the vessel captain.
135 For such tuna products, it is only 
where the National Marine Fisheries Service (NMFS)136 Assistant Administrator has made certain 
determinations that the amended tuna measure also conditions access to the label upon the 
provision of the above certifications by a qualified and approved observer. This additional requirement to provide observer certification(s) is triggered when the NMFS Assistant 
Administrator makes a determination with respect to a specific fishery: (i) within the non-ETP 
purse-seine fishery, that there is a regular and significant association between dolphins and tuna, similar to the association between dolphins and tuna in the ETP; or (ii) within "all other fisheries", 
that there is a regular and significant mortality or serious injury of dolphins.
137 The Panel referred 
to this aspect of the amended tuna measure as the "determination provisions".138 
6.12.  Furthermore, under the amended tuna measure, access to the dolphin-safe label requires 
the segregation of dolphin-safe and non-dolphin-safe tuna from the moment of the catch through 
the entire processing chain. In order to track and verify the dolphin-safe status of tuna, the NMFS 
                                               
129 Section 1385(d)(1)(A) of the DPCIA; and Section 216.91(a)(3) of the implementing regulations. 
130 For purposes of this dispute, th e term "fishery" may be defined by the geographic region in which the 
fishing occurs, the vessel and fishing method used, and the target species. (See Mexico's response to Panel question No. 52, para. 139 (referring to Food and Agri culture Organization, Fisheries Glossary, available at: 
<http://www.fao.org/fi/glossary/> (Panel Exhibit MEX-132)); and United States' response to Panel question No. 21, para. 135) 
131 The Panel indicated that, consistent with the AI DCP, US law, and the reports in the original 
proceedings, it would use the term "lar ge purse-seine vessel" to  refer to purse-seine vessels in the ETP with a 
carrying capacity greater than 363 metric tons, and the te rm "small purse-seine vessel" to refer to purse-seine 
vessels in the ETP with a carrying capacity of 363 metric tons or less. (Panel Report, fn 28 to para. 3.12) 
132 Section 1385(d)(1)(C), in conjunction with Section 1385(d)(2) of the DPCIA; Section 216.91(a)(1) of 
the implementing regulations. 
133 Section 1385(d)(1)(B) of the DPCIA; Section 216.91(a)(2) of the implementing regulations. 
134 Section 1385(d)(1)(D) of the DPCIA; Section 216.91(a)(4) of the implementing regulations. 
135 Only the "no dolphins killed or seriously injured" ce rtification has to be provided by the vessel captain 
for tuna products derived from tuna caught in "all other fisheries". 
136 The NMFS is part of the USDOC. 
137 Under the amended tuna measure,  the requirement to provide obse rver certification(s) is also 
triggered where the NMFS Assistant Administrator has de termined that observers are qualified and authorized 
to make the necessary certification(s), and such ob servers are already on board the vessel. The NMFS 
Assistant Administrator has the authority to make such determinations with respect to all fisheries other than 
the ETP large purse-seine fishery. (Sections 216.91(a)(2)(iii)(B) and 216.91(a)(4)(ii) of the implementing 
regulations) 
138 Panel Report, paras. 7.249 and 7.256. WT/DS381/AB/RW 
 
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 has established the Tuna Tracking and Verification Program (TTVP).139 The basic requirement to 
segregate dolphin-safe from non-dolphin-safe tuna from the time it was caught through unloading and processing applies irrespective of the area of  the ocean in which the tuna was caught and the 
type of vessel that harvested it.
140 More detailed segregation requirements apply, however, to 
tuna products derived from tuna caught in the ETP large purse-seine fishery, given that the 
tracking and verification of tuna caught in this fishery should be conducted consistent with the AIDCP Resolution to Adopt the Modified Syst em for Tracking and Verification of Tuna
141 
(AIDCP Tracking and Verification System).142 
6.13.  Certain documentation requirements pertain to the segregation that is to be conducted by 
persons and entities involved in the catch and processing of tuna. First, all tuna products imported into the United States, regardless of where the tuna is caught and whether the dolphin-safe label 
is used, must be accompanied by a Fisheries Certificate of Origin
143 (Form 370) of the National 
Oceanic and Atmospheric Administration (NOAA).144 Form 370 requires the importer to indicate 
whether it seeks to declare the status of the tuna product as "dolphin-safe", and, if so, to attach 
the certification(s) identified as necessary to establish the dolphin-safe status of the relevant 
category.145 Second, tuna caught by US-flagged large purse-seine vessels fishing in the ETP must 
be accompanied by Tuna Tracking Forms (TTFs), which record certain information regarding each 
tuna set made on a particular fishing trip. One TTF is used to record dolphin-safe sets and another 
one to record non-dolphin-safe sets. For non-US-flagged large purse-seine vessels in the ETP, the TTF numbers must be listed in a certification attached to the Form 370.
146  
6.14.  Tracking and verification requirements also apply regarding the oversight exercised by 
US authorities on importers and US-based persons and entities involved in the catch and 
                                               
139 Panel Report, paras. 3.26 and 3.28; Section 1385(f) of the DPCIA; Section 216.93 of the 
implementing regulations. The provisions establishi ng the TTVP are mainly contained in CFR Title 50, 
Section 216.24, and Sections 216.91-216.93 of the implem enting regulations. Through the use of the TTVP, 
information is collected from domestic tuna processors, US tuna vessels, and importers of tuna products to 
verify whether tuna products  labelled dolphin-safe meet the applicab le conditions. (Panel Report, para. 3.26 
(referring to Original Panel Report, para. 2.31)) 
140 Panel Report, paras. 3.50-3.51. T hus, for all fisheries, during fishing trips, tuna caught in sets 
designated as "dolphin-safe" must be  stored separately from tuna caught  in non-dolphin-safe sets from the 
time of capture through unloading. The vessel captai n or the observer, where applicable, should designate 
separate wells, and any comm ingling of dolphin-safe and non-dolphin-sa fe tuna in any given well disqualifies 
the entire contents of that well from access to the label. (Panel Report, paras. 3.28, 3.31, and 3.51; Sections 216.93(c)(1)(i), 216.93(c)(2)(i), and 216.93(c)(3)(i) of the implementing regulations. See also Section 4 of the AIDCP Tracking and Verification System for tuna caught by a large purse-seine vessel in the 
ETP) Furthermore, tuna offloaded to tr ucks, storage facilities, or carrier ve ssels must be loaded or stored in 
such a way as to maintain and safeguard the identification  of the dolphin-safe or non-dolphin-safe status of the 
tuna as it left the fishing vessel. (Panel Report, paras. 3.31 and 3.51; Sections 216.93(c)(1)(iv), 
216.93(c)(2)(ii), and 216.93(c)(3)(ii) of the implementi ng regulations. See also Section 5 of the AIDCP 
Tracking and Verification System, for tuna caught by a large purse-seine vessel in the ETP) Finally, during 
canning activities of US canneries, non-dolphin-safe tuna may not be mixed in any manner or at any time 
during processing with any dolphin-sa fe tuna or tuna products and may not share the same storage containers, 
cookers, conveyers, tables, or other canning and labe lling machinery. (Panel Report, paras. 3.31 and 3.51; 
Section 216.93(d)(4) of the implementing regulations. See also Section 6(b) of the AIDCP Tracking and Verification System, for tuna caught by a large purse-seine vessel in the ETP) 
141 Adopted on 20 June 2001. (Original Pane l Exhibit MEX-55; Panel Exhibit MEX-36) 
142 Section 216.93(c)(v) of the implementing regulations. 
143 Panel Exhibit MEX-22. 
144 Panel Report, para. 3.49. CFR Title 50, Section 216.24(f)(2), and Sections 216.92(b)(2)(ii) 
and 216.93(f) of the implementing regulations, refer to the need for tuna products imported into the 
United States to be accompanied by a properly completed Form 370. Form 370 requires information regarding, inter alia , the dolphin-safe conditions of the tuna caught duri ng the trip, the ocean area in which the trip took 
place, the fishing gear used, and the vessel's name and flag. (CFR Title 50, Section 216.24(f)(4); see Panel Exhibit MEX-20) 
145 In this respect, Form 370 lists 5 categories for which specific certifications have to be attached: 
(i) tuna caught without using a purse-seine net in a fi shery where no determination of regular and significant 
mortality or serious injury of dolphins has been made; (ii) tuna caught outside the ETP using a purse-seine net 
in a fishery where no determination of  regular and significant association between dolphins and tuna has been 
made; (iii) tuna caught outside the ETP using a purse-se ine net in a fishery where a determination of regular 
and significant association between dolphins and tuna ha s been made; (iv) tuna caught in the ETP by a small 
purse-seine vessel; or (v) tuna caught in  the ETP by a large purse-seine vessel. 
146 Panel Report, paras. 3.28-3.29; Sections 216.92(a)(1) and 216.92(b)(2)(iii) of the implementing 
regulations. The content of the TTFs is described in more detail in section 6.1.1 below. WT/DS381/AB/RW 
 
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 processing of tuna for sale in the US market. The relevant provisions provide for checks to be 
performed on the operation of US canneries147, and require monthly reports from canneries and 
other US tuna processors containing certain specified information, including the certifications required for access to the dolphin-safe label.
148 US authorities may also conduct audits and spot 
checks on any exporter, trans-shipper, importer, processor, or wholesaler/distributor of tuna or 
tuna products.149  
6.15.  The specific conditions applicable to the three categories of fisheries under the amended 
tuna measure are described below.  
6.16.  We recall that the original tuna measure comprised three legal instruments: the DPCIA; the 
original implementing regulations; and the Hoga rth ruling. In the amended tuna measure, the 
DPCIA and the Hogarth ruling remain unchanged. Conversely, the 2013 Final Rule, which the 
United States identifies as the measure taken to comply with the recommendations and rulings of 
the DSB in the original proceedings150, modified certain aspects of Sections 216.91 and 216.93 of 
CFR Title 50.151 The other sections of the implementing regulations challenged by Mexico – notably 
Section 216.92, which sets out requirements for access to the dolphin-safe label that apply 
specifically to tuna products derived from tuna harvested in the ETP by large purse-seine vessels – are unchanged by the 2013 Final Rule. 
6.1.1  The ETP large purse-seine fishery  
6.17.  In order to qualify for the dolphin-safe label, tuna products derived from tuna caught by a 
large purse-seine vessel in the ETP must be accompanied by the following certifications: 
a. a certification from an authorized IATTC or government official that an IDCP-approved 
observer was on board the vessel during the entire trip during which the tuna was 
caught
152; and 
b. a certification from the vessel captain and an IDCP-approved observer that:  
i. no purse-seine net was intentionally deployed on or used to encircle dolphins during 
the same fishing trip153; and  
ii. no dolphins were killed or seriously injured in the sets in which the tuna was 
caught.154 
                                               
147 Panel Report, paras. 3.52 and 7.303 (referring to United States' first written submission to the Panel, 
para. 53). These checks include scheduled or unscheduled inspections by an NMFS representative in order to monitor delivery and verify that dolphin-safe and non- dolphin-safe tuna are clearly identified and remain 
segregated. (Section 216.93(d)(1) of the implementing regulations) 
148 Panel Report, para. 7.303; Sections 216.93(d) and 2 16.93(e) of the implementing regulations. Tuna 
processors must submit report s on all tuna received at the processing facilities containing  information about, 
inter alia , species, condition, weight, ocean area, catcher vess el, gear type, trip dates, carrier name, unloading 
dates, location of unloading, dolphin-safe status, and relevant certifications, as well as the Form 370 (for imported tuna). Where the tuna processor indicates the tu na is eligible for the dolphin-safe label, it must 
enclose the required certifications. (Ibid.) 
149 In order to facilitate monitoring, all such persons and entities must maintain records relating to tuna 
for two years, including the releva nt certifications, form s, and reports submitted to US authorities. 
(Panel Report, para. 7.303 (referring to United States' first written submission to the Panel, para. 52); Section 216.93(g) of the implementing regulations) 
150 Panel Report, para. 3.3. 
151 Panel Report, para. 3.32. See also  Mexico's panel request, p. 1. 
152 Section 1385(d)(2)(B)(ii)(III) of the DPCIA; Section 216.91(a)(1)(i), in conjunction with 
Section 216.92(b)(2)(iii)(A), of the implementing regulations. 
153 Section 1385(d)(2)(B)(i), in conjunction with Section 1385(h)(2)(C) of the DPCIA; 
Section 216.91(a)(1)(iii) of the implementing regulations. 
154 Section 1385(d)(2)(B)(i), in conjunction with Section 1385(h)(2) of the DPCIA; 
Section 216.91(a)(1)(ii) of the implementing regulations. WT/DS381/AB/RW 
 
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 6.18.  These certification requirements should be distinguished from those under the AIDCP, where 
"dolphin-safe" tuna is defined as "tuna captured in sets in which there is no mortality or serious injury of dolphins".
155  
6.19.  As regards the tracking and verification requirements, access to the dolphin-safe label for 
US-flagged large purse-seine vessels fishing in the ETP is conditional upon maintaining TTFs 
consistently with the AIDCP Tracking and Verification System.156 IDCP-approved TTFs, each 
bearing a unique number, are used by the observer to record every set made during a fishing trip. 
Two TTFs are used for each trip, one to record tuna harvested in dolphin-safe sets, and one to 
record tuna harvested in non-dolphin-safe sets.157 A set is "non-dolphin safe" if a dolphin died or 
was seriously injured during the set.158 The IDCP-approved observer159 and the vessel engineer 
each initials the entry following each set, and the vessel captain and the observer review and sign 
both TTFs at the end of the fishing trip certifying that the information on the forms is accurate. 
Tuna caught in sets designated as dolphin safe by the observer must be stored separately from tuna caught in non-dolphin-safe sets from the time of capture through unloading.
160 Independent 
observers monitor the loading and unloading of wells, and individual lots of tuna are assigned the 
corresponding TTF tracking numbers that can be tr aced through each step of production of the 
tuna products.161 
6.20.  The amended tuna measure directly cond itions access to the dolphin-safe label upon 
maintaining TTFs only for tuna products derive d from tuna caught by US-flagged ETP large 
purse-seine vessels.162 In practice, however, the same tracking and verification regime also applies 
in respect of non-US-flagged large purse-seine vessels in the ETP. Under the amended tuna 
measure, tuna products containing tuna harveste d in the ETP by non-US-flagged large purse-seine 
vessels may be labelled dolphin safe only if the vessel belongs to a nation that is a party to the AIDCP.
163 In addition, it is undisputed between the pa rties that the AIDCP requires imposition of 
the same TTF system as the one implemented by the amended tuna measure for US-flagged 
ETP large purse-seine vessels.164 Moreover, Form 370 requires that imports of tuna harvested by 
non-US-flagged ETP large purse-seine vessels, or of tuna products derived from the same, be 
accompanied by documentation from the appropriate IDCP member country certifying that there 
was an IDCP-approved observer on board the vesse l at all times and listing the numbers for the 
                                               
155 AIDCP Tracking and Verification System (Origi nal Panel Exhibit MEX-55; Panel Exhibit MEX-36). 
Thus, under the AIDCP, there is no requirement to certify that a large purse-seine vessel did not set on dolphins. 
156 Section 216.93(c)(1)(v) of the implementing regu lations. See also Panel Report, para. 3.28; and 
AIDCP Tracking and Verification  System (Original Panel Exhibit MEX-55; Panel Exhibit MEX-36). 
157 Panel Report, para. 3.28; Section 216.93(a) of the implementing regulations. The information 
entered on the TTFs for each set includes the date, we ll number, weights by species composition, estimated 
tons loaded, and additional notes, if any. (Ibid.) 
158 Panel Report, para. 3.28 (referring to Section 216.93(c)(1)(i); and United States' first written 
submission to the Panel, fn 63 to para. 35). 
159 The TTF forms must be certified by the independent observers who are required to be on board large 
purse-seine vessels in the ETP. (Panel  Report, para. 3.28 (referring to Mexi co's first written submission to the 
Panel, para. 82)) 
160 Panel Report, paras. 3.31 and 3.50; Section 216.93(c)(1)(i) of the implementing regulations. 
Specifically, if tuna is caught in a set during which a do lphin was killed or seriously injured, that tuna must be 
stored in a well on the vessel separate from dolphin-safe  tuna. If any dolphin-safe tuna is mixed in the same 
well with the non-dolphin-safe tuna, all of the tuna in  that well must be treated as non-dolphin safe. In 
addition, when tuna is to be unloaded from a large purse- seine vessel fishing in the ETP, the captain, managing 
owner, or vessel agent must provide to  US authorities at least 48 hours' notice of the vessel's intended place of 
landing, arrival time, and schedule of unloading. (Section 216.93(c)(1)(ii) of the implementing regulations) 
161 Panel Report, para. 3.50 (referring to Mexico's fi rst written submission to the Panel, para. 92). At 
port, the species and amount of tuna unloaded  are noted in the respective original TTFs. 
(Section 216.93(c)(1)(iii) of the implementing regulations) 
162 Panel Report, paras. 3.47-3.48. 
163 Panel Report, para. 3.29; Section 216.92(b)(2)(i) of the implementing regulations. 
164 Panel Report, para. 3.29 (referring to Mexico's fi rst written submission to the Panel, paras. 85-88). WT/DS381/AB/RW 
 
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 associated TTFs.165 Thus, under the amended tuna measure, tuna products containing tuna caught 
by both US-flagged and non-US-flagged large purse-seine vessels in the ETP have access to the dolphin-safe label only if the handling of the TTFs and the tracking and verification of tuna is conducted consistent with the AIDCP Tracking and Verification System.
166  
6.21.  The certification and tracking and verification requirements applicable to large purse-seine 
vessels in the ETP remain unchanged from the original tuna measure.167  
6.1.2  The non-ETP purse-seine fishery  
6.22.  In order to qualify for the dolphin-safe label, tuna products derived from tuna caught by a 
non-ETP purse-seine vessel168 must be accompanied by a certification from the vessel captain 
that: 
a. no purse-seine net was intentionally deployed on or used to encircle dolphins during the 
same fishing trip; and 
b. no dolphins were killed or seriously injured in the sets in which the tuna was caught.169  
6.23.  Therefore, in principle, certification by the vessel captain is sufficient for tuna products 
derived from tuna caught by purse-seine vessels outside the ETP to gain access to the label. 
Nevertheless, a requirement also to provide these certifications from an observer participating in a national or international programme acceptable to the NMFS Assistant Administrator will be 
triggered, in the event that the NMFS Assistant Ad ministrator determines for a specific fishery that 
regular and significant association occurs between dolphins and tuna similar to the association between dolphins and tuna in the ETP.
170 At the time of the panel request in these Article 21.5 
proceedings, however, no fishery outside the ETP had been determined to have regular and 
significant association between dolphins and tuna similar to that in the ETP.171 
6.24.  Therefore, in order to obtain access to the dolphin-safe label, tuna products derived from 
tuna caught by purse-seine vessels outside the ETP are presently required to have a captain's 
certification that there were "no dolphins killed or seriously injured" and that there was "no setting 
on dolphins". Under the original tuna measure, the only requirement for access to the dolphin-safe 
                                               
165 Panel Report, para. 3.48 (referring to United States' first written submission to the Panel, para. 46). 
Form 370 does not require the provision of the TTFs themselves, but requires that an authorized representative 
of an IDCP member nation certify that: (i) there was an IDCP-approved observer on  board the vessel during 
the entire trip; and (ii) the tuna contained in the shipment was caught according to the dolphin-safe labelling standards of Section 216.91 (i.e. no purse-seine net was intentionally deployed on or to encircle dolphins 
during the fishing trip, and no dolphins were killed or  seriously injured in the sets in which the tuna was 
caught). Form 370 should also contain the harvesting vessel names and list the TTF numbers represented in 
the shipment. (Section 216.92(b)(2)(iii) of the implementing regulations) The associated TTFs contain the captain and observer certifications. (United States' response to Panel question No. 59, para. 292) All 
information concerning the TTFs is maintained by the IATTC and is available for audit and inspection by the members of the AIDCP. (Mexico's response to questioning at the oral hearing) 
166 Panel Report, paras. 3.47-3.48; Section 216.93(c)(v) of the implementing regulations. 
167 Panel Report, paras. 3.39 and 3.47. 
168 Contrary to the labelling conditions applicable to  tuna caught in the ETP, those applying to tuna 
caught outside the ETP do not draw a distinctio n between large and small purse-seine vessels. 
169 Section 1385(d)(1)(B)(ii) of the DPCIA; Section 216.91(a)(2)(iii)(A) of the implementing regulations. 
170 Section 1385(d)(1)(B)(i) of the DPCIA; Section 216. 91(a)(2)(i) of the implementing regulations. 
171 Panel Report, para. 3.22. See also United States ' response to Panel question No. 21, para. 133. 
Under the amended tuna measure, the requirement to pr ovide an observer certification applicable to the 
non-ETP purse-seine fishery is also triggered where the NMFS Assistant Administrator has determined that observers are qualified and authorized to make the necess ary certifications, and such an observer is already on 
board the vessel. (Section 216.91(a)(2)(iii)(B) of the implementing regulations) The NMFS Assistant Administrator has determined that US observers in seven US domestic fisheries are qualified and authorized to 
make the relevant certifications. With respect to these fisheries, therefore, the amended tuna measure conditions access to the dolphin-safe label on the provision of both captain and observer certifications, but only 
when the observer was already on board the vessel for other reasons. Thus, tuna caught on a trip where no 
observer is already on board may still be labelled dolphin- safe with only a captain's certification. (Panel Report, 
para. 3.46 (referring to United States' second written submission to the Panel, para. 128)) WT/DS381/AB/RW 
 
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 label applicable to such tuna products was to provide a captain's certification of "no setting on 
dolphins".172  
6.25.  The amended tuna measure also imposes segregation requirements on this fishery. Tuna 
caught in sets designated as dolphin safe must be stored separately from tuna caught in 
non-dolphin-safe sets from the time of capture through unloading.173 Imported tuna products must 
also be accompanied by a Form 370, which identifies the gear type that was used to catch the tuna, and contains the necessary certifications.
174  
6.1.3  "All other fisheries"  
6.26.  Imported tuna products derived from tuna caught in "all other fisheries", i.e. by 
non-purse-seine vessels in any fishery and small pu rse-seine vessels in the ETP, may be labelled 
dolphin safe when accompanied by a certification by the vessel captain that no dolphins were killed 
or seriously injured during the sets in which the tuna was caught.175  
6.27.  Nevertheless, a requirement also to provide such certification from an observer participating 
in a national or international programme acceptable to the NMFS Assistant Administrator will be 
triggered, in the event that the NMFS Assistant Administrator determines for a certain fishery that 
there is regular and significant mortality or serious injury of dolphins.176 At the time of the panel 
request in these Article 21.5 proceedings, no fishery outside the ETP had been determined to have 
regular and significant mortality or serious injury of dolphins.177 
6.28.  Therefore, in order to obtain access to the dolphin-safe label, tuna products derived from 
tuna caught by non-purse-seine vessels in any fishery and by small purse-seine vessels in the ETP are presently required to have a captain's certification that there were "no dolphins killed or 
seriously injured". Under the original tuna measure, access to the dolphin-safe label for such tuna 
products was not subject to any certification requirements.
178  
6.29.  The tracking and verification requirements a pplicable to this category of fisheries correspond 
to those for tuna caught by purse-seine vessels outside the ETP.179 
6.2  Principal modifications und er the amended tuna measure  
6.30.  In summary, under the amended tuna measure,  all tuna products derived from tuna caught 
on a fishing trip involving setting on dolphins remain disqualified from access to the dolphin-safe 
label. Access to the label is conditional upon the provision of a certification: (a) from both the vessel captain and an IDCP-approved observer that  there were "no dolphins killed or seriously 
injured" and that there was "no setting on dolphins", in the case of tuna products derived from 
tuna caught by a large purse-seine vessel in the ETP
180; (b) from the vessel captain that there 
were "no dolphins killed or seriously injured" and that there was "no setting on dolphins", in the case of tuna products derived from tuna caught by a non-ETP purse-seine vessel; and (c) from the 
vessel captain that there were "no dolphins killed or seriously injured", in the case of tuna 
products derived from tuna caught in "all other fisheries". Therefore, in the absence of any 
                                               
172 Appellate Body Report,  US – Tuna II (Mexico) , para. 292. See also Original Panel Report, para. 2.25. 
173 Panel Report, para. 7.302 (referring to United States' first written submission to the Panel, para. 50). 
174 Panel Report, para. 7.301 (referring to United States' first written submission to the Panel, para. 49). 
175 Section 1385(d)(1)(D) of the DPCIA; Section 216.91(a)(4)(i) of the implementing regulations. 
176 Section 1385(d)(1)(D) of the DPCIA; Section 216.91(a)(4)(iii) of the implementing regulations. 
177 Panel Report, para. 3.22. See also  United States' response to Pane l question No. 21. An observer 
certification for this category of fisheries is also  necessary where the NMFS Assistant Administrator has 
determined that observers are qualified and authorized to make the necessary certification of "no dolphins 
killed or seriously injured", and such observers are al ready on board the vessel. (Section 216.91(a)(4)(ii) of 
the implementing regulations) As noted above, the NMFS Assistant Administrator has determined that 
US observers in seven US domestic fisheries are qualified and authorized to make the relevant certification(s). Certification is required only when the observer is already on board of the vess el for other reasons. (See supra , 
fn 171 to para. 6.23) 
178 Appellate Body Report,  US – Tuna II (Mexico) , para. 248 (referring to Original Panel Report, 
para. 7.532). See also Original Panel Report, para. 2.25. 
179 Section 216.93(c)(3) of the implementing regulations. See supra , para. 6.25.  
180 In addition, a certification must be provided by an  authorized IATTC or gove rnment official that an 
IDCP-approved observer was on board the vessel during the entire trip during which the tuna was caught. WT/DS381/AB/RW 
 
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 determinations made by the NMFS Assistant Administrator181, observer certification is a condition 
for access to the dolphin-safe label only as regards tuna products derived from tuna harvested in the ETP large purse-seine fishery. Moreover, th e amended tuna measure extends the same basic 
condition to segregate dolphin-safe from non-dolphin-safe tuna across fisheries in all ocean areas. 
Specific documentation requirements in the form of TTFs, however, exist only for tuna products 
derived from tuna caught in the ETP large purse-seine fishery. 
6.31.  As the overview above shows, the 2013 Fina l Rule introduced several modifications to the 
conditions for access to the dolphin-safe label, as compared to the original tuna measure. All of the 
changes apply only in respect of tuna caught in fisheries outside the ETP large purse-seine fishery. For such fisheries, the 2013 Final Rule introduced three additional conditions, as set out below. 
6.32.  First, outside the ETP large purse-seine fishery, the amended tuna measure adds as a 
condition of access to the dolphin-safe label for any tuna product the requirement that a 
certification be provided by the vessel captain that  "no dolphins were killed or seriously injured in 
the sets or other gear deployments in which the tuna were caught". No such certification was 
required under the original tuna measure. Rather, under the original tuna measure, such 
certification was required only for tuna products derived from tuna caught by large purse-seine vessels fishing in the ETP.
182 
6.33.  Second, outside the ETP large purse-seine fishery, the amended tuna measure establishes 
as a condition of access to the dolphin-safe label certain segregation requirements whereby tuna caught in sets or other gear deployments designated as dolphin safe must be stored separately from tuna caught in non-dolphin-safe sets or other gear deployments. Such tuna must be 
offloaded and stored in such a way as to maintain segregation as the tuna leaves the fishing 
vessel, as well as during the operations of US tuna canneries and other processors. By contrast, under the original tuna measure, segregation was a condition for access to the dolphin-safe label 
only for tuna products derived from tuna caught by large purse-seine vessels fishing in the ETP.
183 
6.34.  Third, outside the ETP large purse-seine fishery, the amended tuna measure contemplates 
that access to the dolphin-safe label for a particular fishery may also be subject to certification by 
an observer of "no dolphins killed or seriously injured" and, where applicable, of "no setting on 
dolphins"184, where the NMFS Assistant Administrator has determined such observer to be qualified 
and authorized to make the relevant certifications, and the observer is already on board the vessel.
185 Under the original tuna measure, no such possibility to trigger an additional requirement 
for certification by an observer existed as a condition for access to the dolphin-safe label. 
7  ANALYSIS OF THE APPELLATE BODY 7.1  Mexico's claim regarding the amended tuna measure as a whole 
7.1.  We first address Mexico's claim that the Panel erred because it reached findings of 
inconsistency in "a narrow manner rather than concluding that the amended tuna measure, as a 
                                               
181 The NMFS Assistant Administrator may determine, in respect of a sp ecific fishery within the non-ETP 
purse-seine fishery, that there is a regular and significant tuna-dolphin association, similar to the tuna-dolphin association in the ETP, or, in respect of a specific fisher y within "all other fisheries", that there is a regular and 
significant mortality or serious injury of dolphins. 
182 Appellate Body Report, US – Tuna II (Mexico) , paras. 176 and 292; Original Panel Report, 
paras. 2.20 and 2.25(c). Under the original tuna measure,  a certification of "no dolphins killed or seriously 
injured" would also have been required as a condition of access to the dolphin-safe label for fisheries other 
than the ETP large purse-seine fishery, in case the US Secretary of Commerce had made a determination, with respect to a specific fishery within the non-ETP purse-seine fishery, that there was a regular and significant tuna-dolphin association, or, with respect to a non-purs e-seine fishery, that there was a regular and significant 
mortality or serious injury of dolphi ns. No such determinations had been made at the time of the original 
proceedings. (Appellate Body Report, US – Tuna II (Mexico) , para. 249 (referring to Original Panel Report, 
para. 7.534)) 
183 Panel Report, para. 3.31. 
184 In the case of the category of "all other fisheries", access to the dolphin-safe label is conditioned only 
upon a certification of "no dolphins killed or seriously injured". (Section 216.91(a)(4)(i) of the implementing regulations) 
185 In response to questioning at the oral hearing,  the United States and Mexico agreed with this 
description of the three additional conditions and that there are no other significant additional elements introduced to the amended tuna measure by the 2013 Final Rule. WT/DS381/AB/RW 
 
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 whole, is inconsistent with the covered agreements".186 Specifically, Mexico considers that the 
Panel erred in finding that only two of the th ree elements of the amended tuna measure – the 
"certification requirements" and the "tracking and ve rification requirements", but not the "eligibility 
criteria" – are inconsistent with Article 2.1 of th e TBT Agreement and Articles I:1 and III:4 of the 
GATT 1994. Mexico asserts that it challenged the amended tuna measure "as a whole"187, and that 
it differentiated between the three different elements of the measure only in making its arguments regarding the legitimate regulatory distinction that is the focus of the second step in the analysis 
of "treatment no less favourable" under Article 2.1 of the TBT Agreement, and regarding the 
chapeau analysis under Article XX of the GATT 1994. According to Mexico, "it is the amended tuna measure that violates WTO provisions, … not individual elements of the measure considered in isolation".
188 Mexico requests us to modify the findings and conclusions of the Panel and find that 
the amended tuna measure as a whole is inconsis tent with Article 2.1 of the TBT Agreement and 
Articles I:1 and III:4 of the GATT 1994.189 
7.2.  The United States maintains that Mexico's claim should be rejected. First, the United States 
contends that Mexico identifies no legal basis for its assertion that the Panel did not properly 
consider Mexico's claims of discrimination.190 Second, the United States considers that the factual 
premise of Mexico's claim is wrong since Mexico did refer to the certification and tracking and 
verification requirements elsewhere in its submissions, notably in its arguments relating to 
detrimental impact under the first step of the analysis of "treatment no less favourable" under Article 2.1 of the TBT Agreement.
191 Third, the United States maintains that, whether the 
detrimental impact caused by the three elements is assessed together or separately, the Panel's 
analysis would have been the same.192 
7.3.  In addressing this claim by Mexico, we first recount the relevant findings from the panel and 
the Appellate Body in the original proceedings, as well as the relevant findings of the Panel in 
these Article 21.5 proceedings. In the original proc eedings, the panel considered that the separate 
legal instruments challenged by Mexico – consisting of the DPCIA, the original implementing regulations, and the Hogarth ruling – together, se t out the terms of the US dolphin-safe labelling 
regime, and therefore comprised a single measure for purposes of its analysis of Mexico's 
claims.
193 The Appellate Body made a similar statement in its report, further noting that the 
requirements set out in these separate legal instruments, together, "condition eligibility for a 'dolphin-safe' label upon certain documentary evidence that varies depending on the area where 
the tuna contained in the tuna product is harvested and the type of vessel and fishing method by 
which it is harvested".
194 Although both the original panel and the Appellate Body addressed 
different aspects of the conditions for access to the US dolphin-safe label under Article 2.1 of the 
TBT Agreement, including certain certification and tracking and verification requirements195, they 
also each defined, and reached ultimate findings in  respect of, a single measure consisting of "the 
US dolphin-safe labelling provisions".196 
7.4.  The Article 21.5 Panel addressed the scope and content of the amended tuna measure in two 
separate parts of its reasoning. At the outset of its Report, in discussing its jurisdiction under Article 21.5 of the DSU, the Panel considered it "clear" that the Appellate Body's conclusions and recommendations in the original proceedings were meant to apply to the original tuna measure 
"as a whole , including all its components".
197 The Panel also addressed the United States' 
                                               
186 Mexico's other appellan t's submission, para. 66. 
187 Mexico's other appellant' s submission, paras. 65-66. 
188 Mexico's other appellan t's submission, para. 66. 
189 Mexico's Notice of Other Appeal, para. 5; other appellant's submis sion, paras. 71 and 78. 
190 United States' appellee's submission, para. 48. 
191 United States' appellee's submission, para. 50. 
192 United States' appellee's submission, para. 51. 
193 Original Panel Report, para. 7.24; Appellate Body Report, US – Tuna II (Mexico) , para. 2. See also 
Appellate Body Report, US – Tuna II (Mexico) , para. 193: "[T]he US measure establishes a single and legally 
mandated set of requirements for maki ng any statement with respect to the broad subject of 'dolphin-safety' of 
tuna products in the United States." 
194 Appellate Body Report, US – Tuna II (Mexico) , para. 172. 
195 See Original Panel Report, paras. 2.1-2.33; and Appellate Body Report, US – Tuna II (Mexico) , 
paras. 172-177. 
196 Original Panel Report, para. 7.26; Appellate Body Report, US – Tuna II (Mexico) , paras. 2 and 172, 
and fn 357 thereto). See also Original Panel Re port, para. 8.1; and Appellate Body Report, US – Tuna II 
(Mexico) , paras. 407. 
197 Panel Report, paras. 7.11-7.12. (emphasis original) WT/DS381/AB/RW 
 
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 argument that the distinctions drawn by the ch allenged elements of the amended tuna measure 
were unchanged from the original measure an d therefore not subject to these Article 21.5 
proceedings. In that analysis, the Panel stressed that, in finding that the original tuna measure lacked even-handedness, the Appellate Body "did not say that any one particular element of the 
regulatory scheme … was solely responsibl e for this lack of even-handedness."
198 Instead, it was 
"the tuna measure as a whole, with its varying regulatory requirements, that was found to be 
inconsistent with Article 2.1 of the TBT Agreement."199 In particular, the Panel considered that the 
Appellate Body's reference in the plural to "the difference in labelling conditions" and "different 
requirements" indicated that the Appellate Body's findings encompassed various distinctions embedded in the original tuna measure, including in respect of the requirements pertaining to 
certification and tracking and verification.
200 On the basis of this analysis, the Panel concluded that 
it was faced with the legal question of whether the amended tuna measure, including the 
2013 Final Rule, brings the United States into compliance with WTO law, and that it had jurisdiction to consider all of Mexico's claims, including as they relate to the eligibility criteria and 
the certification and tracking and verification requirements.
201 
7.5.  Subsequently, in examining Mexico's claim under Article 2.1 of the TBT Agreement, the Panel 
stated that its task was "to determine whether the amended tuna measure as a whole affords 'less 
favourable treatment' to Mexican tuna and tuna products than to tuna and tuna products from the 
United States and other WTO Members."202 Noting Mexico's explanation that such an analysis 
focuses "on the regulatory distinction that accounts for the detrimental treatment on Mexican tuna products as compared to US tuna products and tuna products originating in other countries"
203, the 
Panel considered that Mexico had identified three "central regulatory distinctions" whose design 
and application give rise to less favourable treatment, namely:  
a. the "eligibility criteria", defined as "[t]he disqualification of setting on dolphins in 
accordance with [the] AIDCP as a fishing method that can be used to catch tuna in the 
ETP in a dolphin-safe manner and the qualification of other fishing methods to catch tuna in a dolphin-safe manner"; 
b. the "certification requirements", defined as "[t]he mandatory independent observer 
requirements for tuna caught in the ETP by setting on dolphins in accordance with the AIDCP and the absence of such requirements for tuna caught outside the ETP using the same and different fishing methods"; and  
c. the "tracking and verification requirements", defined as "[t]he record-keeping and 
verification requirements for tuna caught in the ETP by setting on dolphins in accordance with the AIDCP and the different requirements for tuna caught outside the ETP using 
both the same and different fishing methods".
204  
7.6.  Mexico referred to these collectively as "the difference in labelling conditions and 
requirements", and maintained that this difference means that "all like US tuna products and most 
tuna products of other countries have access to the dolphin-safe label", whereas "the amended 
tuna measure denies access to this label for most Mexican tuna products."205 The Panel also 
recalled the United States' view that any detrimental impact results only from the eligibility criteria, and that the certification and tracking and verification requirements are not relevant 
because they "do not cause the detrimental impact that was the basis for the 
DSB's recommendations and rulings".
206 
                                               
198 Panel Report, para. 7.33. 
199 Panel Report, para. 7.33. See also para. 7.117.  The Panel also considered and rejected the 
United States' contention that the compliance proceedings should be limited to evaluating the 2013 Final Rule. The Panel concluded that its task was "to determine whether the amended tuna measure, including the 2013 
Final Rule, brings the United States into compliance " with the WTO covered agreements. (Ibid., para. 7.24) 
200 Panel Report, paras. 7.35-7.37 (q uoting Appellate Body Report, US – Tuna II (Mexico) , paras. 284 
and 298). 
201 Panel Report, para. 7.43. 
202 Panel Report, para. 7.97. 
203 Panel Report, para. 7.98 (quoting Mexico's first written submission to the Panel, para. 235). 
204 Panel Report, para. 7.98 (quoting Mexico's first written submission to the Panel, para. 236). 
205 Panel Report, para. 7.99 (quoting Mexico's second written submission to the Panel, para. 112). 
206 Panel Report, para. 7.101 (quoting United States' second written submission to the Panel, para. 76). WT/DS381/AB/RW 
 
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 7.7.  The Panel considered that Mexico's argumentation on the detrimental impact caused by the 
certification and tracking and verification requirem ents "developed" over the course of its written 
submissions.207 Although the Panel noted Mexico's contention that it is the differences in labelling 
conditions and requirements of the measure that "together"208 deny Mexican products competitive 
opportunities, the Panel considered that "Mexico's argumentation throughout these proceedings 
made clear that different elements of the amended tuna measure negatively affect Mexican tuna in different ways."
209 The Panel then summarized its understanding of the parties' arguments and the 
structure of the analysis that it would follow, thusly: 
[B]oth parties have structured their arguments throughout these proceedings on the 
basis of the three regulatory distinctions identified by Mexico. That is, while Mexico has argued that the relevant less favourable treatment emerges only or at least most 
clearly when all three distinctions are considered together, it has nevertheless 
presented its arguments on a distinction-by-distinction basis. The United States has followed suit, and presented its argument s on the three regulatory distinctions 
separately. We have decided to follow the approach of the parties in presenting our 
own analysis. Although we will indicate the connections between these distinctions 
where relevant, we conduct our analysis in three parts, considering first the eligibility 
criteria; second, the different certificatio n requirements; and third, the different 
tracking and verification requirements.
210 
7.8.  In the remainder of its Report, the Panel proceeded to undertake separate analyses, and to 
make separate findings, in respect of each of: the "eligibility criteria"; the "different certification 
requirements"; and the "different tracking and verification requirements".  
7.9.  We make several observations about the natu re of Mexico's claim of error on appeal and how 
it relates to the analytical approach that was adopted by the Panel.  
7.10.  First, we note Mexico's contention that it identified and addressed the three different 
elements of the measure as relevant to the second  step of the analysis under Article 2.1 of the 
TBT Agreement (namely, whether any detrimental impact stems exclusively from a legitimate 
regulatory distinction), rather than to the first step of that analysis (namely, whether the measure 
at issue modifies the conditions of competition to the detriment of imported products). According to Mexico, the Panel confused Mexico's argument s relating to these two different steps of the 
analysis and wrongly characterized Mexico's identification of the regulatory distinctions that were 
relevant for the second step of the analysis under Article 2.1 as arguments relating to the 
detrimental impact of the amended tuna measure.
211 Although Mexico claims, generally, that the 
Panel erred by making discrete findings of consis tency and inconsistency in respect of the three 
elements of the measure, instead of in respect of the measure as a whole, we understand that 
Mexico is principally targeting the Panel's decision  to analyse three distinct forms of detrimental 
impact and to segment its analysis of them.212  
7.11.  We further note that the Panel's decision to segment its analysis and separately address the 
three elements of the amended tuna measure ha d repercussions beyond its detrimental impact 
analysis. Indeed, the Panel also segmented its cons ideration of the three elements of the amended 
tuna measure for purposes of the second step of its Article 2.1 analysis, namely, the assessment 
of whether the detrimental impact stems exclusively from a legitimate regulatory distinction. In 
                                               
207 Panel Report, para. 7.102. According to the Pane l, although Mexico focused on one form of 
detrimental impact in its first written submission, in its second written submission, Mexico "elaborated on and clarified" its arguments on detrimenta l impact and, in doing so, "clearly  identifie[d] a distinct type of 
detrimental impact … caused by the different certificatio n and tracking and verification requirements". (Ibid., 
paras. 7.104-7.105, respectively (referring to Mexico's second written submission to the Panel, para. 117)) In the Panel's view, Mexico's arguments reflect "a cl ear and cognizable claim of detrimental impact separate from  
the detrimental impact identified by Mexico as the re sult of the eligibility criteria". (Ibid., para. 7.105 
(emphasis original)) 
208 Panel Report, paras. 7.105 and 7.107 (quoting Mexico's first written submission to the Panel, 
para. 223; and second written submission to the Panel, para. 113, respectively). 
209 Panel Report, para. 7.105. 
210 Panel Report, para. 7.108. 
211 Mexico's other appellant's submission, para . 68 (referring to Panel Report, para. 7.105). 
212 Mexico confirmed at the oral hearing that its cl aim regarding the "measure as a whole" focuses on 
and is most closely tied to the Panel's analysis of detrimental impact. WT/DS381/AB/RW 
 
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 addition, the Panel similarly segmented its analysis concerning Mexico's claims under Articles I:1 
and III:4 of the GATT 1994, as well as the United  States' affirmative defence under Article XX. 
Thus, the Panel divided every stage of its anal ysis under the substantive obligations of the 
TBT Agreement and the GATT 1994 into three parts relating to the "eligibility criteria", the 
"different certification requirements", and the "different tracking and verification requirements."213 
7.12.  In addition, the Panel also made discrete findings  regarding the conformity of each element  
with the applicable legal obligation. Thus, the Panel found that the "eligibility criteria" in the 
amended tuna measure do not accord less favourable treatment to Mexican tuna and tuna 
products than that accorded to like products from the United States and other countries, and are thus not inconsistent with Article 2.1 of the TBT Agreement.
214 Conversely, the Panel separately 
found that each set of "certification requirements" and "tracking and verification requirements" 
accord less favourable treatment to Mexican tuna and tuna products than that accorded to like 
products from the United States and other countries, in violation of Article 2.1 of the TBT Agreement.
215 Similarly, the Panel made three discrete findings that each element of the 
amended tuna measure is inconsistent with Articles I:1 and III:4 of the GATT 1994.216 Finally, the 
Panel made discrete findings with respect to ea ch of the three elements of the amended tuna 
measure under subparagraph (g) and the chapeau of Article XX of the GATT 1994. Although the 
Panel found that each element of the amended tuna measure was provisionally justified under 
Article XX(g), it found that the "eligibility criteria" meet the requirements of the chapeau, whereas the "different certification requirements" and the "d ifferent tracking and verification requirements" 
do not.
217 Thus, the Panel found the "eligibility criteria", but not the "certification requirements" or 
"tracking and verification requirements", to be just ified under Article XX. At no point in its Report 
did the Panel reach a finding of consistency or inconsistency of the amended tuna measure more broadly, or as a whole, with a substantive obligation of the WTO covered agreements.
218 
7.13.  We observe that analysing a measure in a segmented manner may raise concerns when the 
constituent parts of the measure are interrelate d and operate in an integrated way. In  
EC – Asbestos , the Appellate Body criticized the panel's approach of examining the measure at 
issue in two separate stages by focusing first on the prohibitions of the measure, before examining 
the measure's exceptions. Because the scope of the prohibitions of that measure "can only be understood in light of the exceptions", and because "the exceptions in the measure would have no autonomous legal significance in the absence of the prohibitions", the Appellate Body concluded 
that the measure should have been examined "as an integrated whole".
219 In EC – Seal Products , 
the Appellate Body noted that the issue of how best to characterize a measure at issue that consists of several different elements is an issue of "particular significance" in cases where the 
inclusion or exclusion of certain elements  in the definition of the measure "can  affect the legal 
characterization, or substantive analysis of the measure".
220 Noting that the panel had found that 
the relevant legal instruments in that dispute operated in conjunction with each other, that the 
permissive and the prohibitive elements of the me asure were intertwined, and that the parties had 
agreed that the measure at issue should be treated as a single measure, the Appellate Body "consider[ed] it appropriate to draw conclusions re garding the legal characterization of the EU Seal 
Regime as a whole on the basis of an integrated analysis of the constituent parts of the 
measure".
221 The Appellate Body went on to consider that it was only the combined operation of 
                                               
213 See Panel Report, sections 7.5.2 (Article 2.1 of the TBT Agreement), 7.6.1.2 (Article I:1 of the 
GATT 1994), 7.6.2.2 (Article III:4 of the GATT 1994), and 7.7.3.3 (chape au of Article XX of the GATT 1994). 
214 Panel Report, para. 8.2.a. 
215 Panel Report, paras. 8.2.b and 8.2.c. 
216 Panel Report, para. 8.3. 
217 Panel Report, paras. 8.4-8.5. 
218 We note, however, that the Pane l nevertheless recommen ds that the DSB request the United States 
"to bring its measure … found to be inconsistent with  Article 2.1 of the TBT Ag reement and Articles I:1 
and III:4 of the GATT 1994 and not justif ied under Article XX of the GATT  1994, into conformity with its 
obligations under the TBT Agreement and the GATT 1994." (Panel Report, para. 8.6) 
219 Appellate Body Report, EC – Asbestos , para. 64. The Appellate Body also made similar observations 
about the measure at issue in Brazil – Retreaded Tyres , stating that the panel "mig ht have opted for a more 
holistic approach to the measure at issue by examinin g the two elements of [the measure] that relate to 
retreaded tyres together ." The Appellate Body noted, however, that  the panel's analytical approach was not 
appealed, and therefore examined the issues appealed on  the basis of that approa ch. (Appellate Body Report, 
Brazil – Retreaded Tyres , paras. 122-127 (emphasis original)) 
220 Appellate Body Reports, EC – Seal Products , para. 5.20. 
221 Appellate Body Reports, EC – Seal Products , para. 5.20. WT/DS381/AB/RW 
 
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 the various aspects of the measure at issue that gave rise to findings of discrimination under 
Articles I:1 and III:4 of the GATT 1994.222 
7.14.  As a general matter, we do not see that it is necessarily inappropriate for a panel, in 
analysing the conformity of a measure with obligations under the WTO covered agreements, to 
proceed by assessing different elements of the me asure in a sequential manner. Indeed, such an 
approach may, depending on the nature of the measure at issue, be useful, or in some instances critical, to understanding how that measure is designed and applied. In some instances, it may 
even be unobjectionable for a panel to reach separate findings of inconsistency with respect to 
separate elements of a measure, for instance, wh ere the elements of the measure are separable, 
such that they do not depend on each other in substance or in operation.  
7.15.  Other types of measures, however, may not be so easily parsed, and the approach taken in 
scrutinizing such measures must not lead to the isolated consideration of a particular element, or 
particular elements, of a measure in a manner that undermines the legal analysis or leads to a legal conclusion that would have differed had that element been assessed in relation to other 
relevant elements of the measure. In scenarios where the elements of a measure are interrelated, 
and certain elements cannot be properly understood without reference to other elements of the measure, such a segmented approach may create artificial distinctions constituting legal error. We 
also see that, depending on the nature of the le gal obligation at issue, a segmented approach may 
raise concerns when a panel fails to make an overall assessment that synthesizes its reasoning or intermediate conclusions concerning related elements of a measure at issue so as to reach a proper finding of consistency or incons istency in respect of that measure.  
7.16.  In our view, there are various "connections " between the different elements of the amended 
tuna measure that are relevant to the regulatory distinctions examined by the Panel. We observe, 
for instance, that the original panel and the Appellate Body found that the objectives of the 
US dolphin-safe labelling regime are, first, "ens uring that consumers are not misled or deceived 
about whether tuna products contain tuna that was caught in a manner that adversely affects dolphins", and, second, "contributing to the protecti on of dolphins, by ensuring that the US market 
is not used to encourage fishing fleets to catch tuna in a manner that adversely affects 
dolphins".
223 These are also the objectives of the amended tuna measure.224 Thus, like the original 
measure, the amended tuna measure establishes a labelling regime consisting of various elements that are aimed at fulfilling the same objectives. 
7.17.  In addition to sharing a common purpose,  the elements of the amended tuna measure are 
also highly interconnected. For instance, the two substantive conditions for access to the dolphin-safe label – namely, the conditions of "no setting on dolphins" and "no dolphins killed or 
seriously injured" – are both defined by, and veri fied through, the associated certification and 
tracking and verification requirements. For all covered fisheries, compliance with these conditions is demonstrated through the provision of certain certifications.
225 The measure also establishes a 
programme for the tracking of tuna that is based on the substantive conditions and that depends, 
inter alia , on the certifications that must accompany tuna products derived from tuna meeting 
these conditions throughout the catch and subsequent processing of such tuna.226 In our view, 
these various provisions underscore the interrela ted nature of the different elements of the 
amended tuna measure examined by the Panel. As the original panel and the Appellate Body 
                                               
222 Appellate Body Reports, EC – Seal Products , paras. 5.188-5.189. 
223 Appellate Body Report, US – Tuna II (Mexico) , para. 325 (quoting Original Panel Report, 
paras. 7.401, 7.413, and 7.425). 
224 Panel Report, para. 7.523. 
225 See Section 1385(d)(1)-(2) of the DPCIA; and Sections 216.91 and 216.92 of the implementing 
regulations. Section 216.91(a)(1) of the implementing regula tions, for example, identifies three conditions that 
must be met for the dolphin-safe labe l to be used for tuna products cont aining tuna caught in the ETP large 
purse-seine fishery, the first of whic h is that "the documentation requirements for dolphin-safe tuna under 
§216.92 and 216.93 are met". 
226 As can be seen from our above description of th e measure at issue, many of the tracking and 
verification requirements pertain to satisfaction of the "no dolphins killed or seriously injured" condition, 
although certain such requirements, including those relating  to verification, audit, an d spot checks of records, 
as well as through provision of the Form 370 by non-US vessels, also concern a demonstration or verification that the "no setting on dolphins" condition has been met in respect of purse-seine fisheries. See also 
Section 1385(f) of the DPCIA, which requires the i ssuance of regulations to implement the statutory 
requirements, "including regulations to establish a tracking and verifica tion program that provides for the 
effective tracking of tuna labelled under [Section 1385(d)]". WT/DS381/AB/RW 
 
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 noted, the existence of the substantive conditions of "no setting on dolphins" and "no dolphins 
killed or seriously injured" would be meaningle ss in the absence of requirements that enforce 
compliance with such standards.227 Under these circumstances, we do not consider that the 
substantive conditions for gaining access to the dolphin-safe label can be properly understood 
without reference to the certification and tracking and verification requirements that define, and 
demonstrate compliance with, those very conditions. 
7.18.  At several points in its analysis, the Panel acknowledged the interrelationships between the 
various elements of the amended tuna measure. As we have noted, in discussing its jurisdiction 
under Article 21.5, the Panel confirmed that it would examine the amended tuna measure as a whole, including its varying regulatory requirements.
228 In addition, after noting that the 
Appellate Body's findings encompassed various distinctions embedded in the original tuna 
measure, including the certification and tracking and verification requirements, the Panel stated 
that the US dolphin-safe labelling regime "necessarily includes" not only the certification requirements, but also the various documentation requirements constituting "the mechanisms by 
which compliance with that standard is monitored and demonstrated".
229 The Panel subsequently 
underscored not only that the amended tuna meas ure, and in particular the 2013 Final Rule, 
"relates directly to the substantive declarations or certifications that must be made before a catch 
of tuna can be labelled as being dolphin-safe", but that, in addition, the tracking and verification 
mechanisms "are central aspects of the tuna me asure, working together with the substantive 
certification requirements".230 On that basis, the Panel disagreed with the United States that the 
tracking and verification requirements are "separable" from the certification rules set out in the 
2013 Final Rule.231 
7.19.  In the light of this understanding by the Panel of the manner in which the various elements 
of the amended tuna measure interrelate, it is not clear to us why the Panel considered it 
appropriate to conduct its subsequent analysis in a segmented manner that addressed particular 
elements of the measure in isolation from other re lated elements. For instance, in its consideration 
of the "eligibility criteria", the Panel adopted a particularly limited focus by examining only the 
substantive condition that tuna products not be derived from tuna caught on a trip involving 
setting on dolphins. As we have noted, however, t una products that meet this condition are eligible 
for the dolphin-safe label only if they also meet another  substantive condition, namely, that no 
dolphins were killed or seriously injured in the sets in which the tuna were caught. By focusing 
only on the criteria related to the "no setting on dolphins" condition, the Panel's analysis excluded 
consideration of whether the products concerned also meet the "no dolphins killed or seriously injured" condition. Similarly, in its analysis of the "certification requirements" and "tracking and 
verification requirements", the Panel considered that such requirements "are relevant only to tuna 
eligible and intended to receive the dolphin-safe label" – that is, only to "tuna [not] caught by setting on dolphins".
232 In so proceeding, the Panel did not assess how the certification and 
tracking and verification requirements, which the Panel itself considered to be an integral part of 
the overall measure, interrelate with each other and with the substantive conditions for access to the dolphin-safe label. The Panel's approach is even more surprising given its earlier conclusion that the tracking and verification requirements are not "separable" from the certification 
requirements set out in the 2013 Final Rule. Although the Panel stated that it would "indicate the 
connections between these distinctions where relevant"
233, we do not see that the Panel, in its 
analysis of whether the amended tuna measure br ought the United States into conformity with 
provisions of the TBT Agreement and the GATT 1994, explained the "connections" between the 
different elements of the measure giving rise to the distinctions examined by the Panel.  
7.20.  We further recall that the original tuna measure, like the amended tuna measure, contained 
provisions relating to qualifying fishing methods, certification, and tracking and verification. While 
the amended tuna measure has introduced certain ch anges, as explained in our description of the 
                                               
227 In the original proceedings, the Appellate Body upheld the original panel's reasoning that the 
imposition of a substantive requirement that no dolphins  be killed or seriously injured outside the ETP would 
not be practically relevant "if it is assumed that  it cannot be verified". (Appellate Body Report, US – Tuna II 
(Mexico) , para. 294 (quoting Original Panel Report, para. 7.541)) 
228 Panel Report, para. 7.33. 
229 Panel Report, fn 125 to para. 7.37. 
230 Panel Report, para. 7.40. 
231 Panel Report, paras. 7.40-7.41. 
232 Panel Report, para. 7.143. 
233 Panel Report, para. 7.108. WT/DS381/AB/RW 
 
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 measure at issue, these have not altered the overall architecture of the US dolphin-safe labelling 
regime by somehow undermining the existence of interrelationships among its constituent elements. If anything, the changes reflected in the amended tuna measure serve to reinforce the 
nature of those interrelationships. The Panel, howe ver, did not adopt an analytical approach to the 
measure similar to the one used by the panel and the Appellate Body in the original proceedings. 
In these circumstances, and given the Panel's statements regarding the need to examine the amended tuna measure as a whole and in an integrated manner, we would have expected some 
discussion by the Panel, during the course, or at the conclusion, of its segmented analysis, as to 
how the various findings related to one another, and on what basis the Panel proceeded to make discrete findings of consistency and inconsistency notwithstanding the interrelationships among the various elements of the measure.  
7.21.  In sum, although the Panel had, in discussi ng its jurisdiction under Article 21.5 of the DSU, 
emphasized the interlinkages between elements of  the amended tuna measure, it subsequently 
conducted a segmented analysis that isolated consideration of each element of the measure 
without accounting for the manner in which the elements are interrelated, and without aggregating 
or synthesizing its analyses or findings relating  to those elements before reaching its ultimate 
conclusions as to the consistency or inconsistency of the amended tuna measure. We recognize 
that a proper appreciation of the extent to which the interrelationships are relevant, and the extent 
to which a segmented analysis had a bearing on the outcome of the legal analysis, will be a function of the particular legal obligation under examination – in this case, those set out in Article 2.1 of the TBT Agreement and Articles I:1,  III:4, and XX of the GATT 1994. At this stage of 
our Report, however, we see no merit in analysing the consequences of the Panel's segmented 
approach in the abstract. Rather, we will assess whether the Panel's approach amounted to, or led it to commit, legal error when we examine the specific claims on appeal that the participants have 
directed at the Panel's analysis and findings. 
7.2  Article 2.1 of the TBT Agreement 7.22.  The United States and Mexico each appeals certain aspects of the Panel's reasoning and 
findings under Article 2.1 of the TBT Agreement. Mexico requests us to reverse the Panel's finding 
that the eligibility criteria in the amended tuna  measure are consistent with Article 2.1 of the 
TBT Agreement
234, whereas the United States seeks reversal of the Panel's findings that the 
different certification requirements and the different tracking and verification requirements in the 
amended tuna measure are inconsistent with Article 2.1 of the TBT Agreement.235  
7.23.  Our analysis is divided into three parts. Fi rst, we begin by recalling relevant jurisprudence 
on the legal standard to be applied under Articl e 2.1 of the TBT Agreement. Second, we consider 
the issues raised by the United States on appe al with regard to the Panel's application of 
Article 2.1 to the measure at issue, and in particular its analysis of whether the amended tuna measure, and the discrete sets of requirements set out therein, adversely modify the conditions of 
competition for Mexican tuna products in the US market. Third, we consider the respective claims 
of error raised by the United States and Mexico in connection with the Panel's analysis of whether the detrimental impact that it found the measure at issue to have on Mexican tuna products in the United States' market stems exclusively from a legitimate regulatory distinction. In this third part 
of our analysis, we begin by assessing the United States' claim that the Panel erred in its 
articulation of the legal standard under the second step of the "treatment no less favourable" analysis under Article 2.1, before turning to consider the various issues raised by the participants 
in connection with the Panel's application of the second step of the "treatment no less favourable" 
analysis under Article 2.1 to the amended tuna measure and to the discrete sets of requirements set out therein. 
                                               
234 Panel Report, para. 8.2.a. 
235 Panel Report, paras. 8.2.b and 8.2.c. WT/DS381/AB/RW 
 
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 7.2.1  "Treatment no less favourable" under Article 2.1 of the TBT Agreement 
7.24.  Article 2 of the TBT Agreement addresses the "Preparation, Adoption and Application of 
Technical Regulations by Central Government Bodies", and its first paragraph provides that, "[w]ith respect to their central government bodies": 
Members shall ensure that in respect of tec hnical regulations, products imported from 
the territory of any Member shall be accorded treatment no less favourable than that accorded to like products of national origin and to like products originating in any 
other country.  
7.25.  Article 2.1 contains both a national treatment obligation and a most-favoured-nation 
treatment obligation. In order to establish a violation of either obligation, a complainant must demonstrate three elements: (i) that the measure at issue is a "technical regulation" within the 
meaning of Annex 1.1 to the TBT Agreement; (ii) that the relevant products are "like products"; 
and (iii) that the measure at issue accords less favourable treatment to the imported products than to the relevant group of like products.
236 As the United States' appeal with respect to the 
Panel's interpretation of Article 2.1 concerns only the third of these elements, we limit our 
summary below to recalling key aspects of the "treatment no less favourable" requirement in Article 2.1, as explained by the Appellate Body in previous reports.  
7.26.  In US – Clove Cigarettes , the Appellate Body identified a two-step analysis to be followed in 
examining whether the technical regulation at issue accords less favourable treatment to imported products under Article 2.1 of the TBT Agreement.
237 The Appellate Body indicated that the first 
step of the analysis focuses on whether the technica l regulation at issue modifies the conditions of 
competition to the detriment of such imported products vis-à-vis like products of domestic origin 
and/or like products originating in any other country.238 However, a finding that the measure at 
issue modifies the conditions of competition to the detriment of imported products is not sufficient 
to demonstrate less favourable treatment under Article 2.1.239 Rather, a second step of analysis is 
needed, namely, an assessment of whether the detrimental impact on imports stems exclusively from a legitimate regulatory distinction rather than reflecting discrimination against the group of 
imported products.
240 Where the detrimental impact caused by a technical regulation stems 
exclusively from a legitimate regulatory distinction, such technical regulation is not according less favourable treatment to imported products within the meaning of Article 2.1 of the TBT Agreement. 
7.27.  Regarding the first step in the analysis, the scope of the comparison to be undertaken in 
assessing whether there is less favourable treatment of imports depends on the products that a panel has found to be "like" for the purposes of Article 2.1.
241 Once the like products have been 
properly identified, Article 2.1 requires a pane l to compare, on the one hand, the treatment 
accorded under the measure at issue to the "group" of like products imported from the complaining Member with, on the other hand, that accorded to the "group" of like domestic 
products and/or the "group" of like products originating in any other country.
242 In making this 
comparison, any adverse impact on competitive opportunities for imported products vis-à-vis like domestic products that is caused by a particular measure may potentially be relevant to a detrimental impact finding.
243  
                                               
236 Appellate Body Reports, US – Clove Cigarettes , para. 87; US – Tuna II (Mexico) , para. 202.  
237 Appellate Body Report, US – Clove Cigarettes , paras. 182 and 215. See also Appellate Body Reports, 
US – Tuna II (Mexico) , para. 215; and US – COOL , para. 271. 
238 Appellate Body Report, US – Clove Cigarettes , para. 180. See also Appellate Body Reports,  
US – Tuna II (Mexico) , para. 215; and US – COOL , para. 268. 
239 Appellate Body Report, US – Clove Cigarettes , paras. 182 and 215. See also Appellate Body Reports, 
US – Tuna II (Mexico) , para. 215; and US – COOL , para. 271. 
240 Appellate Body Report, US – Clove Cigarettes , para. 182. See also Appellate Body Report,  
US – Tuna II (Mexico) , para. 215. 
241 Appellate Body Report, US – Clove Cigarettes , para. 192. 
242 Appellate Body Reports,  US – Clove Cigarettes , para. 193; US – Tuna II (Mexico) , para. 215;  
US – COOL , para. 268. See also EC – Asbestos , para. 100. 
243 Appellate Body Report, US – Tuna II (Mexico) , para. 225. WT/DS381/AB/RW 
 
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 7.28.  That there is a difference in treatment between products of different country origins is 
neither necessary, nor sufficient to establish detrimental impact.244 By the same token, the 
application of formally identical legal provisions to imported and like products of different origins may nevertheless entail a detrimental impact on the competitive conditions for the imported 
products.
245 In examining whether a technical regulation has a de facto detrimental impact, a 
panel "must take into consideration 'the totality of facts and circumstances before it'"246 and 
assess any "implications" for competitive conditions  "discernible from the design, structure, and 
expected operation of the measure".247 Such an examination must take account of all the relevant 
features of the market, which may include the particular characteristics of the industry at issue, the relative market shares in a given industry, consumer preferences, and historical trade patterns.
248 That is, a panel must examine the operation of the particular technical regulation at 
issue in the particular market in which it is applied.249 
7.29.  Article 2.1 of the TBT Agreement, like Ar ticles I:1 and III:4 of the GATT 1994, protects the 
equality of competitive opportunities between like products rather than any particular volume of 
trade.250 Therefore, a panel is not required under Article 2.1 to ground its legal conclusions on 
evidence of the actual trade effects of the technical regulation in the relevant market.251 Nor is a 
panel limited, in analysing detrimental impact, to an examination of the operation of the technical 
regulation at issue within the confines of scenarios that are representative of current patterns of 
trade.252 Rather, a party may make its case and a panel may reach conclusions concerning 
detrimental impact on the basis of evidence and arguments going to the "design, structure, and 
expected operation of the measure".253 At the same time, a finding of detrimental impact cannot 
rest on simple assertion254, and a panel should not "ascribe undue weight to the effect of a 
technical regulation in any hypothetical scenario".255  
7.30.  Turning to the second step of the "treatment no less favourable" analysis under Article 2.1 
of the TBT Agreement, we note that the Appellate  Body has emphasized that the specific context 
provided by other provisions of the TBT Agreemen t is instructive in understanding the expression 
"treatment no less favourable" under Article 2.1. The specific context provided by, in particular, 
Annex 1.1, Article 2.2, and the second, fifth, and sixth recitals of the preamble, "supports a 
reading that Article 2.1 does not operate to prohibit a priori  any restriction on international 
trade".256 The sixth recital sheds light on the meaning and ambit of the "treatment no less 
favourable" requirement in Article 2.1 by making clear that technical regulations may pursue 
                                               
244 Appellate Body Reports, Korea – Various Measures on Beef , para. 137; Thailand – Cigarettes 
(Philippines) , para. 128; Dominican Republic – Import  and Sale of Cigarettes , para. 96. 
245 We note that, in Korea – Various Measures on Beef , the Appellate Body considered that the 
GATT panel in US – Section 337 Tariff Act  had persuasively explained that: 
On the one hand, contracting partie s may apply to imported products different  formal legal 
requirements if doing so would accord imported  products more favourable treatment. On the 
other hand, it also has to be recognised that  there may be cases where the application of 
formally identical  legal provisions would in practice accord less favourable treatment to imported 
products and a contracting party might thus have to apply different legal provisions to imported 
products to ensure that the treatment accord ed them is in fact no less favourable. 
(Appellate Body Report, Korea – Various Measures on Beef , para. 136 (quoting GATT Panel Report,  
US – Section 337 Tariff Act , BISD 36S/345, para. 5.11 (emphasis original))) 
246 Appellate Body Reports,  US – COOL , para. 269 (quoting Appellate Body Report, US – Clove 
Cigarettes , para. 206). 
247 Appellate Body Reports, US – COOL , para. 269 (quoting Appellate Body Report, Thailand – Cigarettes 
(Philippines) , para. 130). 
248 Appellate Body Reports, US – COOL , para. 269.  
249 Appellate Body Reports, US – COOL , para. 269.  
250 See Appellate Body Reports, EC – Seal Products , para. 5.82; US – Clove Cigarettes , para. 176; 
China – Publications and Audiovisual Products , para. 305; Korea – Various Measures on Beef , paras. 135-136; 
Thailand – Cigarettes (Philippines) , para. 126; Japan – Alcoholic Beverages II , p. 16, DSR 1996:1, p. 109; and 
Korea – Alcoholic Beverages , para. 127; and Panel Reports, US – COOL , para. 7.571; Colombia – Ports of 
Entry , para. 7.236; and Argentina – Hides and Leather , para. 11.20. 
251 Appellate Body Reports, US – COOL , para. 325. 
252 Appellate Body Reports, US – COOL (Article 21.5 – Canada and Mexico) , para. 5.15. 
253 Appellate Body Reports, US – COOL , para. 269 (quoting Appellate Body Report, Thailand – Cigarettes 
(Philippines) , para. 130). 
254 Appellate Body Report, US – FSC (Article 21.5 – EC) , para. 215. (emphasis omitted) 
255 Appellate Body Reports, US – COOL (Article 21.5 – Canada and Mexico) , para. 5.16. 
256 Appellate Body Reports, US – COOL , para. 268. See also Appellate Body Reports, US – Clove 
Cigarettes , para. 171; and US – Tuna II (Mexico) , para. 212. WT/DS381/AB/RW 
 
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 legitimate objectives but must not be applied in a manner that would constitute a means of 
arbitrary or unjustifiable discrimination.257 Article 2.1 should not be read to mean that any 
distinctions, in particular ones that are based exclusively  on such particular product characteristics, 
or on particular processes and production methods, would per se  constitute less favourable 
treatment within the meaning of Article 2.1.258 Rather, some distinctions that entail detrimental 
impact may not amount to less favourable treatment under Article 2.1. This would be the case, in particular, where the detrimental impact on imports stems exclusively from a legitimate regulatory 
distinction. 
7.31.  In determining whether the detrimental impact on imports stems exclusively from a 
legitimate regulatory distinction, a panel must carefully scrutinize whether the technical regulation at issue is even-handed in its design, architecture, revealing structure, operation, and application 
in the light of the particular circumstances of the case.
259 The Appellate Body has pointed out that 
where a regulatory distinction is not designed and applied in an even-handed manner – because, 
for example, it is designed or applied in a ma nner that constitutes a means of arbitrary or 
unjustifiable discrimination – that distinction cannot be considered "legitimate", and thus the 
detrimental impact will reflect discrimination prohibited under Article 2.1.260 Therefore, a measure 
that involves "arbitrary or unjustifiable discrimination" would not be designed and applied in an 
"even-handed manner". At the same time, the fact  that a measure is designed in a manner that 
constitutes a means of arbitrary or unjustifiable discrimination is not the only way in which a 
measure may lack even-handedness, such that th e detrimental impact cannot be said to stem 
exclusively from legitimate regulatory distinctions.  
7.32.  With respect to the burden of showing th at a technical regulation is inconsistent with 
Article 2.1 of the TBT Agreement, as we have already explained, a finding that a technical regulation modifies the conditions of competition to the detriment of imported products is not 
sufficient to demonstrate less favourable treatment under Article 2.1
261 because a regulation that 
has a de facto  detrimental impact on imports will not be inconsistent with Article 2.1 when such 
impact stems exclusively from a legitimate regulatory distinction.262 With respect to the burden of 
demonstrating these elements of Article 2.1, in the original proceedings, the Appellate Body noted 
that it is well established that the burden of proof rests upon the party, whether complaining or defending, who asserts the affirmative of a particular claim or defence.
263 Where the complaining 
party has met the burden of making its prima facie  case, it is then for the responding party to 
rebut that showing.264 Under Article 2.1, this means that a complainant must show that, under the 
technical regulation at issue, the treatment accorded to imported products is less favourable than that accorded to like domestic products or like products originating in any other country. Provided 
that it has shown detrimental impact, a complainant may, therefore, make a prima facie  showing 
of less favourable treatment by, for example, adducing evidence and arguments showing that the measure is not even-handed, which would suggest that the measure is inconsistent with 
Article 2.1.
265 If, however, the respondent shows that the detrimental impact on imported products 
                                               
257 Appellate Body Reports, US – Clove Cigarettes , para. 173; US – Tuna II (Mexico) , para. 213. The 
sixth recital of the preamble of the TBT Agreement recognizes that a WTO Member may take measures necessary for, inter alia , the protection of human, animal or plant lif e or health, of the environment, or for the 
prevention of deceptive practices, at the levels it cons iders appropriate, subject to the requirement that such 
measures "are not applied in a manner which would constitute a means of arbitrary or unjustifiable 
discrimination" or a "disguised restriction on internatio nal trade" and are "otherwise in accordance with the 
provisions of this Agreement". 
258 Appellate Body Reports, US – Clove Cigarettes , para. 169; US – Tuna II (Mexico) , para. 211;   
US – COOL , para. 268. 
259 Appellate Body Report, US – Clove Cigarettes , para. 182. 
260 Appellate Body Reports, US – COOL , para. 271.  
261 Appellate Body Reports, US – Tuna II (Mexico) , para. 215;  US – Clove Cigarettes , paras. 182 
and 215; US – COOL , para. 271. 
262 Appellate Body Reports, US – COOL , para. 271;  US – Clove Cigarettes , para. 182; US – Tuna II 
(Mexico) , para. 215. 
263 Appellate Body Reports, US – Tuna II (Mexico) , para. 216;  US – Wool Shirts and Blouses , p. 14, 
DSR 1997:1, p. 335; US – COOL , para. 272. The Appellate Body has indicated that, "where a regulatory 
distinction is not designed and applied in an even-handed manner – be cause, for example, it is designed or 
applied in a manner that constitutes a means of arbitr ary or unjustifiable discrimination – that distinction 
cannot be considered 'legitimate', and thus the detrimen tal impact will reflect discrimination prohibited under 
Article 2.1." (Appellate Body Reports,  US – COOL , para. 271) 
264 Appellate Body Report, US – Tuna II (Mexico) , para. 216. 
265 Appellate Body Reports, US – Tuna II (Mexico) , para. 216; US – Clove Cigarettes , paras. 182 
and 215. WT/DS381/AB/RW 
 
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 stems exclusively from a legitimate regulatory distinction, it follows that the challenged measure is 
not inconsistent with Article 2.1.266 
7.33.  Of course, there is no set formula as to how a complainant must make out its case. Rather, 
the nature and scope of arguments and evidence required to establish a prima facie  case will 
necessarily vary according to the facts of the case267 and from measure to measure, provision to 
provision, and case to case.268 Moreover, these rules and principles of WTO jurisprudence must not 
be applied in an unduly formalistic or mechanistic fashion269, nor inhibit the substantive analysis 
that must be undertaken by a panel. In seeking to make out a claim of de facto  discrimination 
under Article 2.1, a complainant may elect to rely on some or all of the same regulatory distinctions and evidence as to how they are desi gned and operate in the relevant market both to 
establish de facto  detrimental impact and to show that th e regulatory distinctions drawn under the 
technical regulation involve a lack of even-handedness. While the complaining party bears the 
burden of making its prima facie  case, the responding party must prove the case it seeks to make 
in response
270, and each party bears the burden of substantiating the assertions that it makes.271 
In our view, having promulgated the technical regulation containing the regulatory distinctions that 
result in the detrimental impact, the responding Member will be best situated to adduce the arguments and evidence needed to explain why, contrary to the complainant's assertions, the 
technical regulation is even-handed and thus why the detrimental impact on imports stems 
exclusively from a legitimate regulatory distinction. Thus, the Appellate Body noted in the original proceedings that, although the burden of proof to show that the US dolphin-safe labelling 
provisions were inconsistent with Article 2.1 was on Mexico as the complainant, it was for the 
United States to support its assertion that its regime was "calibrated" to the risks to dolphins 
arising from different fishing methods in different areas of the oceans.
272  
7.34.  We are not certain that, in its discussion of  the burden of proof under Article 2.1, the Panel 
fully recognized the responsibilities of both part ies in this regard. To us, the Panel's reasoning 
seems to cast the burden of proof as an entirely binary issue. For example, the Panel stated that, 
on one possible understanding of the burden of proof, "it is Mexico that bears the burden of 
showing prima facie  both that the amended tuna measure modifies the conditions of competition in 
the United States' market to the detriment of Mexican tuna and tuna products and that such 
detrimental treatment reflects discrimination because it does not stem exclusively from a legitimate regulatory distinction and is not even-handed".
273 Alternatively, the Panel explained, the 
burden of proof might be allocated such that, if Mexico established detrimental impact, "the Panel 
would need to determine whether the United States has made a prima facie  case that this 
detrimental treatment nevertheless stems exclusivel y from a legitimate regulatory distinction."274 
These statements are not in consonance with th e Appellate Body's discussion of the burden of 
proof in the original proceedings and seem to reflect a mechanistic articulation of the function of 
                                               
266 Appellate Body Report, US – Tuna II (Mexico) , para. 216. 
267 Appellate Body Report, US – Tuna II (Mexico) , para. 216. 
268 Appellate Body Reports, Chile – Price Band System (Article 21.5 – Argentina) , para. 134; US – Wool 
Shirts and Blouses , p. 14, DSR 1997:I, p. 335; US – Carbon Steel , para. 157. 
269 For instance, "a panel is not obliged, in every instance, to make an explicit finding that a complaining 
party has met its burden to establish a prima facie  case in respect of each element of a particular claim, or that 
the responding party has effectively rebutted a prima facie  case. Thus, a panel is not required to make an 
explicit ruling that a complaining party has established a prima facie  case of inconsiste ncy before examining 
the responding party's defence and ev idence." (Appella te Body Report, Chile – Price Band System  
(Article 21.5 – Argentina) , para. 135 (referring to Appellate Body Reports, Thailand – H-Beams , para. 134; and 
Korea – Dairy , para. 145)) 
270 Appellate Body Report, Japan – Apples , para. 154. 
271 Appellate Body Reports, US – Tuna II (Mexico) , para. 283;  Japan – Apples , para. 157; US – Wool 
Shirts and Blouses , p. 14, DSR 1997:1, p. 335; EC – Hormones , para. 98. 
272 Appellate Body Report, US – Tuna II (Mexico) , para. 283. The question before the Appellate Body 
was thus "whether the United States [had] demonstrated that this difference in labelling conditions is a legitimate regulatory distinction, and hence whether the detrimental impact of the measure stem[med] 
exclusively from such a distinction rath er than reflecting discrimination." (Ibid., para. 284 (emphasis omitted)) 
273 Panel Report, para. 7.59. (original emphasis) 
274 Panel Report, para. 7.236. See also para. 7.58. WT/DS381/AB/RW 
 
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 the burden of proof275,  a s  w e l l  a s  a n  i m p r o p e r  c o n f l a t i o n  o f  t h e  b u r d e n  a n d  t h e  s t a n d a r d  o f  
proof.276  
7.35.  Moreover, we have reservations about the reason given by the Panel for choosing the 
approach that it did, namely, that "in the present proceedings both parties agree" on the allocation 
of the burden of proof.277 In the analysis leading up to its decision to adopt this approach, the 
Panel expressed its "uncertainty"278 about what the Appellate Body had previously found with 
respect to the burden of proving less favourable tr eatment under Article 2.1. The Panel went on to 
set out in some detail the views of the parties and the third parties with respect to the allocation of 
the burden of proof, stating that it was "mindful that there may be systemic reasons for favouring"
279 an approach different from the one agreed  upon by the parties, and then decided 
nevertheless to adopt the parties' agreed approach to allocating the burden of proof.280 To us, an 
approach whereby a panel allocates the burden of proof under a provision of the covered 
agreements solely on the basis of the parties' ag reement would not be consistent with its duty to 
interpret and apply such provision. We recognize that, in this context, the Panel stated that it was 
aware that it was not "bound by the legal interpretations offered by the parties or the 
third-parties".281 Yet, it does appear to have been the parties' joint endorsement that ultimately 
induced the Panel to adopt the approach that it did. In any event, neither participant has 
challenged on appeal the Panel's approach to the burden of proof, and we will proceed on the basis 
of the Appellate Body's articulation of the applicable burden of proof as outlined in paragraphs 7.32 and 7.33 above. 
7.2.2  Less favourable treatment – Detrimental impact  
7.36.  We now turn to the issue of whether the Pa nel erred in its analysis of whether the amended 
tuna measure modifies the conditions of competition to the detriment of Mexican tuna products in the US market.  
7.37.  The United States requests us to reverse the Panel's findings of detrimental impact with 
respect to the certification and tracking and verification requirements.
282 First, the United States 
claims that, by grounding its findings on the di fference in costs and burdens imposed on tuna 
products originating inside and outside the ETP large purse-seine fishery, the Panel improperly 
made the case for Mexico, given that Mexico had not presented arguments and evidence concerning such costs and burdens in its written submissions.
283 Second, according to the 
United States, the Panel erred in finding that the certification and tracking and verification 
requirements impose different costs and burdens on tuna products derived from tuna caught inside 
the ETP large purse-seine fishery as compared to tuna products derived from tuna caught in other fisheries. Even assuming that any such differences  exist, the United States claims that the Panel 
failed to explain how such different costs and burd ens modify the conditions of competition to the 
detriment of Mexican tuna products in the ligh t of the relevant features of the US market.
284 
Rather, the Panel erred by reaching conclusions on detrimental impact "without making any factual 
findings" other than to establish the existence of different certification and tracking and verification 
                                               
275 The Panel stated, for example, that  "according to the allocation of the burden of proof … it is for 
Mexico to show,  prima facie  and in the first instance, that the different [certification and] tracking and 
verification requirements are not even-handed, because, fo r example, they reflect discrimination. Only if 
Mexico makes this showing will the burden shift to the United States to show that the different [certification and] tracking and verification requir ements in fact stem excl usively from a legitimate regulatory distinction." 
(Panel Report, para. 7.389. (emphasis original) See also paras. 7.195 and 7.236) 
276 Thus, for example, the Panel expressed concern th at, if the burden of proving that detrimental 
impact does not stem exclusively from a legitimate regulatory distinction belongs to the respondent, then "complainants may decide not to bring a claim under Arti cle 2.1 of the TBT Agreement if they are of the view 
that they could obtain essentially the same outcome (i.e. a finding of less favourable treatment) under the GATT 1994 without having to prove as many facts ." (Panel Report, para. 7.58 (emphasis added)) 
277 Panel Report, para. 7.59. 
278 Panel Report, para. 7.51. 
279 Panel Report, para. 7.58. 
280 Panel Report, paras. 7.46-7.59. 
281 Panel Report, para. 7.59 (referri ng to Appellate Body Report, EC – Tariff Preferences , para. 105). 
282 United States' appellant's submission, paras. 92, 135, 287, and 332 (referring to Panel Report, 
paras. 7.162, 7.382, 8.2.b, and 8.2.c). 
283 United States' appellant's submission, paras. 136-144 and 288-295. 
284 United States' appellant's submission, paras. 145-155 and 314-319. WT/DS381/AB/RW 
 
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 requirements.285 Third, the United States submits that the Panel did not properly establish a 
genuine relationship between the certification and tracking and verification requirements under the amended tuna measure, on the one hand, and any detrimental impact on the competitive 
opportunities for Mexican tuna products, on the other hand. In its view, no such relationship 
exists. The amended tuna measure does not subject Mexican tuna products to its certification and 
tracking and verification requirements because those products are derived from tuna caught by setting on dolphins and are therefore disqualified from access to the dolphin-safe label from the 
outset. Further, the United States argues, since the certification and tracking and verification 
requirements for tuna products derived from tuna caught in the ETP large purse-seine fishery are mandated by the AIDCP, any detrimental impact on Mexican tuna products is not attributable to the amended tuna measure, but rather to Mexico's international obligations.
286 
7.38.  Mexico, for its part, maintains that the question of whether the amended tuna measure 
modifies the conditions of competition to the detriment of its tuna products in the US market was settled by the panel and the Appellate Body in the original proceedings. In particular, Mexico 
recalls the Appellate Body's finding that the detrimental impact of the original tuna measure on 
Mexican tuna products was caused by the fact that most such products "contain tuna caught by setting on dolphins in the ETP and are therefore not eligible for a 'dolphin-safe' label", whereas 
"most tuna products from the United States and other countries that are sold in the US market 
contain tuna caught by other fishing methods outside the ETP and are therefore eligible for a 'dolphin-safe' label."
287 The amended tuna measure "does not change those aspects of the design 
and structure of the original tuna measure" that were found to cause detrimental impact.288 In 
other words, the amended tuna measure continues to permit all US tuna products and most tuna 
products from other countries to have access to the dolphin-safe label, while it denies access to this label for most Mexican tuna products.
289 Therefore, in Mexico's view, the Appellate Body's 
findings, which have not been challenged by the parties in the current proceedings, "definitively 
establish" that the US dolphin-safe labelling regime modifies the competitive conditions in the US market to the detriment of Mexican tuna products. At the oral hearing, Mexico clarified that this 
argument relates to its claim on appeal, discussed in section 7.1 above, that the Panel erred in 
analysing the three sets of requirements under the amended tuna measure – the "eligibility criteria", the "certification requirements", an d the "tracking and verification requirements" – 
separately, as opposed to focusing on the WTO-consistency of the measure as a whole.
290 
According to Mexico, these three sets of requirements "operate together" to modify the 
competitive conditions in the US market to the detriment of Mexican tuna products.291 Because the 
amended measure as a whole continues to have a detrimental impact on Mexican tuna products in 
the US market, Mexico argues that it neither soug ht to, nor needed to, es tablish "independent and 
complete prima facie  cases" of detrimental impact "for each of the three [sets of] labelling 
conditions and requirements".292 
7.39.  As a third participant, the European Union echoes Mexico's view and contends that a 
detrimental impact assessment must focus on what is caused by the measure at issue as a whole – that is, the entire "set of relevant regulatory distinctions".
293 According to the 
European Union, the main aspects that led the original panel and the Appellate Body to find that 
the US dolphin-safe labelling regime has a detrimental impact on Mexican tuna products "remain 
unchanged".294 In the European Union's view, the Panel should have taken into account the 
relevant findings from the original proceedings, and should have refrained from undertaking an 
                                               
285 United States' appellant's submission, para. 155 (quoting Appellate Body Report,  
Thailand – Cigarettes (Philippines) , para. 138). 
286 United States' appellant's submission, paras. 167-184 and 327-331. 
287 Mexico's appellee's submission, para. 41 (quoting Appella te Body Report, US – Tuna II (Mexico) , 
para. 284). 
288 Mexico's appellee's submission, para. 43. See also para. 50. 
289 Mexico's appellee's submission, para. 44. 
290 Mexico's other appellan t's submission, para. 66. 
291 Mexico's appellee's submission, para. 51. 
292 Mexico's appellee's submission, para. 48. See also paras. 107, 117, and 156. 
293 European Union's third participant's su bmission, para. 11. (emphasis omitted) 
294 European Union's third participant's submission, pa ra. 12. The European Unio n points, in particular, 
to the "significant commercial value" of the dolphin-sa fe label in the US market; the "asymmetry" in treatment 
between tuna caught in the ETP large purse-seine fishery and tuna caught in other fi sheries; and the "genuine 
and substantial relationship" between the original measure and the detrimental impact on Mexican tuna and 
tuna products – despite the intervention of some "pri vate choices" on the part of US consumers and the 
Mexican fleet. (Ibid., paras. 9 and 12) WT/DS381/AB/RW 
 
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 analysis of whether the certification and tracking and verification requirements, "considered in 
isolation", have a detrimental impact.295 The "increased" certification and tracking and verification 
requirements bear only on the question of wh ether the amended tuna measure is even-handed.296 
In the light of the above, the European Union suggests that we declare the Panel's findings 
regarding the detrimental impact of the certificat ion and tracking and verification requirements 
moot and of no legal effect.297 
7.40.  In addressing the issues raised by the pa rticipants on appeal, we begin by providing an 
overview of the panel and Appellate Body findings in the original proceedings concerning the 
detrimental impact of the original tuna measure, as well as the Panel's findings in these compliance proceedings concerning the detrimental impact of the amended tuna measure. We then examine whether the Panel erred in its analysis of whether the various elements constituting 
the amended tuna measure modify the conditions of competition to the detriment of Mexican tuna 
products in the US market within the meaning of Article 2.1. 
7.2.2.1  The findings of detrimental impact in the original proceedings  
7.41.  Before the original panel, Mexico claimed that the original tuna measure modified the 
conditions of competition in the US market to the detriment of its tuna products because: (i) Mexican tuna products are derived almost exclusively from tuna caught in the ETP by setting on 
dolphins, and cannot therefore access the dolphin-safe label; (ii) US tuna products are derived 
from tuna caught outside the ETP using other fishing methods, and are thus eligible for access to the label; (iii) most consumers and retailers are sensitive to issues related to dolphin mortality and will not purchase tuna products that are not designated as "dolphin safe"; and (iv) most 
US canneries will not accept non-dolphin-safe tuna for processing.
298  
7.42.  The original panel agreed with Mexico that the dolphin-safe label has "significant commercial 
value on the US market for tuna products", and th at therefore access to such label constitutes an 
"advantage" on that market.299 The original panel then considered whether the regulatory 
distinction drawn by the original tuna measure – whereby tuna products containing tuna caught by setting on dolphins could not access the dolphin-safe label, whereas tuna products containing tuna 
caught by other fishing methods were eligible for such label – modified the conditions of 
competition to the detriment of Mexican tuna products vis-à-vis like products from the United States and other countries. In its view, this regulatory distinction did not, de jure , place 
Mexican tuna products "at a disadvantage as compared to US and other imported tuna 
products"
300, because "any fleet operating anywhere in the world must comply with the 
requirement" not to set on dolphins.301  
7.43.  Turning to examine whether the original measure nonetheless had a de facto  detrimental 
impact in the light of the fishing practices of the Mexican and other fishing fleets, the original panel 
noted that, since 1990, when the first version of the DPCIA was adopted, US vessels had gradually discontinued setting on dolphins to catch tuna in the ETP, whereas the Mexican fleet had not 
abandoned the use of such fishing technique.
302 Thus, the original panel considered that any 
difference in the relative competitive situations of Mexican and other tuna products was not attributable to the original measure, but was rather the result of the choices of private actors
303, 
including "Mexico's own fishing fleet and canners".304 It further held that, for similar reasons, 
"[t]he existence of additional costs for some operators as a result of factors such as existing 
practices also does not necessarily … imply" a detrimental impact on the competitive conditions of such operators' products.
305 In the light of the above, the original panel was not persuaded that 
                                               
295 European Union's third participant's su bmission, para. 12. (emphasis omitted) 
296 European Union's third participant's submission, paras. 12, 17, 20, 24, and 47. 
297 European Union's third participant's submission, paras. 14, 17, 20, and 48. 
298 Original Panel Report, para. 7.253. 
299 Original Panel Report, paras. 7.289 and 7.291. Th is finding was not appealed. (See Appellate Body 
Report, US – Tuna II (Mexico) , para. 233) 
300 Original Panel Report, para. 7.311. 
301 Original Panel Report, para. 7.305. 
302 Original Panel Report, paras. 7.327-7.331. 
303 Original Panel Report, para. 7.334. 
304 Original Panel Report, para. 7.378. 
305 Original Panel Report, para. 7.342. WT/DS381/AB/RW 
 
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 the original tuna measure modified the conditions of competition to the detriment of Mexican tuna 
products as compared to like products originating in the United States or in any other country.306  
7.44.  The Appellate Body noted that the panel ha d made the following factual findings: (i) "the 
Mexican tuna cannery industry is vertically integrated, and the major Mexican tuna products 
producers and canneries own their vessels, which operate in the ETP"; (ii) "at least two thirds of 
Mexico's purse seine tuna fleet fishes in the ETP by setting on dolphins" and is "therefore fishing for tuna that would not be eligible to be contained in a 'dolphin-safe' tuna product under the US 
dolphin-safe labelling provisions"; (iii) "the US fleet currently does not practice setting on dolphins 
in the ETP"; and (iv) "as the practices of the US and Mexican tuna fleets currently stand, most tuna caught by Mexican vessels, being caught in the ETP by setting on dolphins, would not be eligible for inclusion in a dolphin-safe product under the US dolphin-safe labelling provisions", 
while "most tuna caught by US vessels is potentially eligible for the label".
307  
7.45.  In the Appellate Body's view, such findings "clearly establish[ed]" that the lack of access to 
the dolphin-safe label of tuna products containing tuna caught by setting on dolphins had a 
detrimental impact on the competitive opportunities  of Mexican tuna products in the US market.308 
The Appellate Body stated that a detrimental impact determination does not hinge on whether imported products "could" somehow obtain market access "by complying with all applicable 
conditions", but rather on "whether the contested measure modifies the conditions of competition 
to the detriment of imported products".
309 The Appellate Body disagreed with the Panel that the 
different competitive situations of Mexican and other tuna products were not attributable to the original tuna measure, but rather to the choices of private actors. For the Appellate Body, the 
relevant question for assessing whether a genuine  relationship exists between a measure and an 
adverse impact on competitive opportunities for imported products is whether "governmental action 'affects the conditions under which like goods, domestic and imported, compete in the 
market within a Member's territory'."
310 The Appellate Body took the view that it was the 
"governmental action" in the form of adoption and application of the original tuna measure that had modified the conditions of competition in the market to the detriment of Mexican tuna 
products, and thus that the detrimental impact flowed from the original measure.
311 In its opinion, 
"[t]he fact that the detrimental impact on Mexican tuna products may involve some element of private choice [did] not … relieve the United States of responsibility under the TBT Agreement."
312 
7.46.  Based on the foregoing, the Appellate Body  concluded that the original tuna measure did, 
indeed, modify the conditions of competition in the US market to the detriment of Mexican tuna 
products.313 Later in its report, the Appellate Body summarized its conclusions on detrimental 
impact in the following terms: 
[T]he detrimental impact of the measure on Mexican tuna products is caused by the 
fact that most Mexican tuna products contain tuna caught by setting on dolphins in the ETP and are therefore not eligible for a "dolphin-safe" label, whereas most tuna 
products from the United States and other countries that are sold in the US market 
contain tuna caught by other fishing methods outside the ETP and are therefore eligible for a "dolphin-safe" label. The aspect of the measure that causes the detrimental impact on Mexican tuna products is thus the difference in labelling 
conditions for tuna products containing tuna caught by setting on dolphins in the ETP, 
on the one hand, and for tuna products containing tuna caught by other fishing methods outside the ETP, on the other hand.
314 
                                               
306 Original Panel Report, para. 7.374. 
307 Appellate Body Report, US – Tuna II (Mexico) , para. 234 (quoting Original Panel Report, 
paras. 7.310, 7.314, and 7.316-7.317). 
308 Appellate Body Report, US – Tuna II (Mexico) , para. 235. 
309 Appellate Body Report, US – Tuna II (Mexico) , para. 221. 
310 Appellate Body Report, US – Tuna II (Mexico) , para. 236 (quoting Appellate Body Report,  
Korea – Various Measures on Beef , para. 149). 
311 Appellate Body Report, US – Tuna II (Mexico) , para. 239. 
312 Appellate Body Report, US – Tuna II (Mexico) , para. 239. 
313 Appellate Body Report, US – Tuna II (Mexico) , para. 240. 
314 Appellate Body Report, US – Tuna II (Mexico) , para. 284. WT/DS381/AB/RW 
 
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 7.2.2.2  The Panel's findings 
7.47.  Before the Article 21.5 Panel, both Mexico and the United States indicated that the 
detrimental impact of the amended tuna measure is the same as that of the original measure. Mexico's principal argument with respect to detrimental impact was that "[t]he key elements of the 
design and structure of the measure that operated  together to deny competitive opportunities … 
have not been changed."
315 In particular, the detrimental impact found by the panel and the 
Appellate Body in the original proceedings – namely, the disqualification of most Mexican tuna 
products from access to the dolphin-safe label, as opposed to the eligibility of most like products 
originating in the United States and in other countries for such label – continues to exist.316 The 
United States, for its part, did not contest the A ppellate Body's conclusions on detrimental impact 
in the original proceedings317, which, in its view, focused on access to the dolphin-safe label in the 
light of "the fishing practices of the US and Mexican fleets".318 According to the United States, the 
exclusion of tuna products derived from tuna caught by setting on dolphins " is the detrimental 
impact".319 In the United States' opinion, the certification and tracking and verification 
requirements were "not relevant" to the Panel's detrimental impact analysis320, because Mexican 
tuna products containing tuna caught by setting on dolphins would still be ineligible for the dolphin-safe label even if those requirements did not exist.
321 
7.48.  The Panel took the view that Mexico's arguments concerning the detrimental impact of the 
amended tuna measure had "developed" over the course of the proceedings.322 At first, Mexico 
had focused on the fact that the amended measure denies access to the dolphin-safe label to most Mexican tuna products, whereas all US tuna products and most like products from other countries 
have access to the label.
323 Subsequently, Mexico explained that it is "the absence of sufficient 
fishing method qualification, record keeping, verification and observer requirements" outside the ETP large purse-seine fishery that causes Mexican tuna products to "los[e] competitive 
opportunities to tuna products that may be inaccurately labelled as dolphin-safe".
324 For the Panel, 
Mexico's later arguments "constitute[d] a clear and cognizable claim of detrimental impact" that was "distinct" and "separate" from the type of detrimental impact that Mexico identified as 
resulting from the eligibility criteria.
325 While the eligibility criteria are "responsible for the fact that 
most Mexican tuna products are ineligible to receive the label", the certification and tracking and verification requirements provide a "competitive advantage" to non-Mexican tuna products.
326  
7.49.  Accordingly, as discussed in section 7.1 above, the Panel segmented its assessment of the 
consistency of the amended tuna measure with Article 2.1 into three separate analyses, one for 
each of the three sets of requirements constitu ting the measure – the "eligibility criteria", the 
"different certification requirements", and the "different tracking and verification requirements".327  
7.50.  The Panel began by assessing the consistency with Article 2.1 of the "eligibility criteria" – 
i.e. the regulatory distinction between tuna products derived from tuna caught by setting on dolphins and tuna products derived from tuna caught by other fishing methods.
328 It observed that 
these criteria lay "at the very heart of the original proceedings".329 For this first set of 
requirements, the Panel did not conduct a two-step analysis of: (i) whether the eligibility criteria have a detrimental impact on the competitive conditions for Mexican tuna products in the US market; and, if so, (ii) whether such detrim ental impact stems exclusively from a legitimate 
                                               
315 Mexico's first written submission to the Panel, para. 223. 
316 Mexico's first written submission to the Panel, paras. 52, 315, and 329. See also e.g. Mexico's 
second written submission to the Panel, paras. 104, 203, and 220-221; opening statement at the Panel 
meeting, para. 50; and response to Panel question No. 7, paras. 20-21. 
317 See Panel Report, para. 7.446. 
318 United States' second written su bmission to the Panel, para. 68. 
319 United States' first written submission to the Panel, para. 223. (emphasis original) 
320 United States' second written su bmission to the Panel, para. 75. 
321 United States' first written submission to the Panel, para. 223.  
322 Panel Report, para. 7.102. 
323 Panel Report, para. 7.102 (referring to Mexico's first written submission to the Panel, para. 232). 
324 Panel Report, para. 7.104 (quoting Mexico's seco nd written submission to the Panel, para. 117). 
(emphasis omitted) 
325 Panel Report, para. 7.105. (emphasis omitted) 
326 Panel Report, para. 7.105. (emphasis omitted) 
327 Panel Report, para. 7.108. 
328 Panel Report, section 7.5.2.2. 
329 Panel Report, para. 7.118. WT/DS381/AB/RW 
 
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 regulatory distinction. Rather, it took the view that, as an Article 21.5 panel, it ought to "rely upon 
factual and legal conclusions made by the original panel and the Appellate Body, at least in the absence of compelling new evidence that would render those previous findings unsustainable."
330 
The Panel understood the Appellate Body in the original proceedings to have "clearly found" that 
the United States is entitled to treat setting on dolphins differently from other fishing methods331 
and that, therefore, the disqualification from the dolphin-safe label of tuna caught by setting on dolphins, coupled with the qualification for the label of tuna caught by other fishing methods, is 
not inconsistent with Article 2.1.
332 The Panel did not consider it appropriate to "re-open this 
inquiry" and, instead, stated that it would "respe ct and reaffirm" the Appellate Body's finding that, 
"to the extent that they modify the conditions of competition in the US market to the detriment of 
Mexican … tuna products, the eligibility criteria are even-handed, and, accordingly, are not 
inconsistent with Article 2.1 of the TBT Agreement."333 
7.51.  The Panel then moved on to assess, in turn, the consistency with Article 2.1 of the "different 
certification requirements"334 and the "different tracking and verification requirements".335 For 
each of these sets of requirements, the Pane l did conduct a two-step analysis aimed at 
establishing: (i) whether the set of requirements in question has a detrimental impact on the competitive conditions of Mexican tuna products in the US market; and, if so, (ii) whether such 
detrimental impact stems exclusively from a legitimate regulatory distinction. 
7.52.  In examining whether the different "certifi cation requirements" – i.e. the requirement that 
certifications be made by both captains and observers in the ETP large purse-seine fishery, as opposed to the requirement of captain certification only for "all other fisheries" – give rise to 
detrimental impact on Mexican tuna products in the US market, the Panel grounded its reasoning 
on the costs of implementing observer coverage. It noted the United States' recognition that "observer coverage involves the expenditure of significant resources"
336, as well as the parties' 
acknowledgement that "the costs of implementing observer coverage can be significant."337 In the 
light of the above, the Panel found that, by no t requiring independent observer coverage in 
fisheries other than the ETP large purse-seine fishery, the certification requirements "impose a 
lesser burden" on tuna products derived from tuna caught in those other fisheries.338 Having so 
found, the Panel considered it unnecessary to also "make a definitive finding"339 on 
Mexico's allegation that the certification requirements "make it more likely that tuna caught outside the ETP large purse seine fishery will be inaccurately labelled".
340 Albeit seeing "some 
merit" in Mexico's allegation, the Panel opined that "a definitive finding on this point would require 
a complex and detailed analysis of all of the various factors that may lead to tuna being inaccurately labelled."
341 
7.53.  Based on the foregoing, the Panel conclude d that the certification requirements modify the 
conditions of competition to the detriment of Mexican tuna products in the US market.342 
7.54.  Subsequently, the Panel addressed the alleged detrimental impact of the "tracking and 
verification requirements" under the amended tuna measure – i.e. the different "record-keeping 
and verification requirements" for tuna products containing tuna caught in the ETP large purse-seine fishery and for tuna products containing tuna caught in other fisheries.
343 The Panel 
                                               
330 Panel Report, para. 7.119. 
331 Panel Report, para. 7.122. See also para. 7.123. 
332 Panel Report, para. 7.126. 
333 Panel Report, para. 7.126. 
334 Panel Report, section 7.5.2.4. 
335 Panel Report, section 7.5.2.5. 
336 Panel Report, para. 7.162 (referring to United States' first written submission to the Panel, 
paras. 265-266). 
337 Panel Report, para. 7.162 (referring, inter alia , to United States' and Me xico's responses to Panel 
questions Nos. 48-50). In particular, the Panel noted that the United States had acknowledged that the cost of establishing and maintaining observer  programmes "'impose[s] [an] enor mous barrier to entry' into the 
US tuna market, and may cost hundreds of millions of do llars." (Ibid. (quoting United States' response to Panel 
question No. 49, para. 266)) 
338 Panel Report, para. 7.162. 
339 Panel Report, para. 7.169. 
340 Panel Report, para. 7.163. 
341 Panel Report, para. 7.169. 
342 Panel Report, para. 7.179. 
343 Panel Report, para. 7.98 (referring to Mexico's first written submission to the Panel, para. 236). WT/DS381/AB/RW 
 
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 found that the tracking and verification requirements for tuna products originating in the ETP large 
purse-seine fishery, which are largely mandated by the AIDCP, bring with them "strict obligations"
344 aimed at ensuring the segregation of tuna caught without killing or seriously 
injuring dolphins from tuna caught in sets involving dolphin mortality or serious injury throughout 
the whole production process – including storage on board fishing vessels, unloading at port, 
brokering through intermediaries, trans-shipment, partial processing into loins, and canning.345 
With respect to tuna products derived from tuna caught outside the ETP large purse-seine fishery, 
the Panel took note of the United States' explanations as to how the amended tuna measure 
provides for verification that there has been segregation between dolphin-safe and non-dolphin-safe tuna. The Panel found that the United States ensures that tuna has been properly tracked and verified primarily through cannery audits – including spot checks – aimed at acquiring 
"the documents that track particular lots received by the canneries from the vessel trip on which 
the tuna was caught."
346 Canneries are also required to submit monthly reports containing 
information about the tuna received and processed,  including dolphin-safe status, weight, ocean of 
capture, gear type used, type of catcher vessel, tr ip dates, carrier name, unloading dates, place of 
unloading, and, if the tuna products are to be labelled as dolphin safe, the required certifications.
347 Other forms of control on the part of US authorities include retail spot checks – 
which work "in essentially the same way as cannery audits"348 – and inspections on the high seas, 
in US waters, or at US ports.349 
7.55.  The Panel held that the tracking and verifi cation requirements applied inside and outside the 
ETP large purse-seine fishery, respectively, present "crucial differences" in terms of "depth, 
accuracy, and degree of government oversight".350 In terms of depth, the Panel found that the 
system applied to the ETP large purse-seine fishery allows the trace-back of tuna "all the way to the particular set  in which the tuna was caught and the particular well in which it was stored ".
351 
Conversely, the system applied to other fisherie s allows the trace-back of tuna only "to the vessel  
and trip on which it was caught".352 As for accuracy, the Panel found that, in respect of the 
ETP large purse-seine fishery, the TTFs and the relevant certifications accompany particular 
batches of tuna "throughout the fishing and prod uction process, from the point of catch right 
through to the point of retail".353 In contrast, for tuna harvested in other fisheries, the 
United States had not shown how the relevant certifications are kept with particular batches of tuna up until the tuna reaches the cannery.
354 Finally, as regards government oversight, the Panel 
took the view that, in respect of the ETP large purse-seine fishery, information concerning every 
stage of tuna harvest and processing is made av ailable to the competent authorities by sending 
them copies of the TTFs and notifying th em whenever ownership of tuna changes.355 Conversely, 
for tuna harvested in other fisheries, the competent authorities receive information on the origin 
and history of the tuna only from the canneries themselves – through the mandatory monthly reports or audits and spot checks – and are thus not able to go "behind the documents" and 
appraise the veracity of such information.
356 
7.56.  In the light of the above, the Panel conc luded that the tracking and verification system 
applied to tuna caught in fisheries other than the ETP large purse-seine fishery presents some "major gaps in coverage"
357, which "strongly suggest[]" that the system in question is 
                                               
344 Panel Report, para. 7.296. 
345 Panel Report, paras. 3.47-3.52. 
346 Panel Report, para. 7.308 (quoting United States ' response to Panel question No. 44, para. 240). 
347 Panel Report, para. 7.303. 
348 Panel Report, para. 7.312. 
349 Panel Report, para. 7.307. 
350 Panel Report, para. 7.354. (emphasis omitted) 
351 Panel Report, para. 7.355. (emphasis original) 
352 Panel Report, para. 7.356. (emphasis original) In this respect, the Panel reviewed two exhibits that, 
according to the United States, show that the tracking and verification system appl ied to fisheries other than 
the ETP large purse-seine fishery allows tuna to be traced back to the specific set in which the tuna was caught 
and the specific well in which it was stored. The Panel disagreed that such exhibits show that it is possible to trace tuna back as far as th e United States contended. Rather, it took the view that the system only allows 
tracing tuna back to the trip during which it was harvested. (Ibid., paras. 7.357-7.359) 
353 Panel Report, para. 7.360. 
354 Panel Report, para. 7.361. 
355 Panel Report, para. 7.364. 
356 Panel Report, para. 7.365. 
357 Panel Report, para. 7.369 (quoting Mexico's comment s on United States' response to Panel question 
No. 43, para. 172). WT/DS381/AB/RW 
 
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 "significantly less burdensome" than the system in place for tuna caught inside the ETP large 
purse-seine fishery.358 Having made such a finding, the Panel did not consider it necessary to 
further examine Mexico's allegation that the differences in the two sets of tracking and verification requirements make it more likely that tuna products derived from tuna caught outside the 
ETP large purse-seine fishery will be incorrectly labelled. While the Panel did see "some merit" in 
Mexico's allegation, it took the view that a definitive finding on this point would require "a detailed technical analysis of the system's effective operation".
359 
7.57.  Based on the foregoing, the Panel found that the tracking and verification requirements 
modify the conditions of competition in the US market to the detriment of Mexican tuna products.
360 
7.58.  In each of its two analyses of detrimen tal impact, the Panel addressed the United States' 
argument that any detrimental impact suffered by Mexican tuna products because of the 
certification and tracking and verification requirements applied to tuna products derived from tuna caught in the ETP large purse-seine fishery "stems from the AIDCP regime" rather than from the 
amended tuna measure, with the consequence that there is no "genuine relationship" between the 
measure and any detrimental impact on competitive opportunities for Mexican tuna products.
361 
The Panel found that, while the AIDCP imposes certain certification and tracking and verification 
requirements on the ETP large purse-seine fishery, "it has nothing to say" about analogous 
requirements applicable to other fisheries.362 The amended tuna measure, by contrast, imposes 
certain certification and tracking and verification requirements on the ETP large purse-seine fishery and different such requirements on other fisheries. Thus, the Panel reasoned that "[i]t is the 
amended tuna measure" that, within the same re gulatory framework, "provides for two sets of 
rules for access to the dolphin-safe label – one set for tuna caught by large purse seine vessels in the ETP, and another set for all other tuna."
363 In the Panel's view, the fact that one element of the 
regulatory distinction – i.e. the requirements applicable to the ETP large purse-seine fishery – is 
mandated by international obligations does not detract from a conclusion that the distinction as a whole is attributable to "the design and structure of the amended tuna measure itself".
364 
7.2.2.3  Whether the Panel erred in its an alysis of the detrimental impact of the 
amended tuna measure 
7.59.  At the outset of our review of the Panel's detrimental impact analysis, we recall that, in 
examining whether a technical regulation entails de facto  detrimental impact, a panel must take 
into consideration "the totality of facts and circumstances before it" and assess any implications for 
competitive conditions "discernible from the design, structure, and expected operation of the measure."
365 Such examination must also "take account of all the relevant features of the market, 
which may include the particular characteristics of the industry at issue, the relative market shares 
in a given industry, consumer preferences, and historical trade patterns" – that is, "the operation of the particular technical regulation at issue in the particular market in which it is applied."
366 
Thus, a panel conducting a de facto  detrimental impact analysis under Article 2.1 of the 
TBT Agreement ought to take into account both the design and structure of the measure at issue and the way in which the measure operates (or can be expected to operate) in the light of the relevant features of the market concerned. 
7.60.  We further recall that, as was found in the original proceedings and as both parties have 
acknowledged in these compliance proceedings, access to the dolphin-safe label constitutes an 
                                               
358 Panel Report, paras. 7.369-7.370. 
359 Panel Report, para. 7.372. 
360 Panel Report, para. 7.382. 
361 Panel Report, para. 7.171 (quoting United States' first written submission to the Panel, paras. 226 
and 295). 
362 Panel Report, para. 7.177. 
363 Panel Report, para. 7.177. 
364 Panel Report, para. 7.177. See also para. 7.294. 
365 Appellate Body Reports, US – COOL , para. 269 (quoting, respectively, Appellate Body Reports,  
US – Clove Cigarettes , para. 206; and Thailand – Cigarettes (Philippines) , para. 130). 
366 Appellate Body Reports, US – COOL , para. 269 (referring to Panel Report, Mexico – Taxes on Soft 
Drinks , para. 8.119; and Appellate Body Reports, Korea – Various Measures on Beef , para. 145; and  
US – Tuna II (Mexico) , paras. 233-234). WT/DS381/AB/RW 
 
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 "advantage" on the US market for tuna products by virtue of that label's "significant commercial 
value".367  
7.61.  In section 7.1 above, we expressed the view that it is only through the design and operation 
of all its labelling conditions combined that the amended tuna measure establishes access to the 
dolphin-safe label for tuna products sold in the US market. Indeed, different labelling conditions 
may affect access to the dolphin-safe label for groups of like tuna products in different ways. For instance, while the disqualification of tuna products derived from tuna caught by setting on 
dolphins means that most Mexican tuna products are not eligible for the dolphin-safe label
368, 
other elements of the amended tuna measure – such as the new certification and tracking and verification requirements imposed outside the ETP large purse-seine fishery by virtue of the 2013 Final Rule – may also exclude some tuna products of US or other origin from access to the label. 
The various sets of requirements under the amended tuna measure may have varying degrees of 
significance for the question of whether Mexican tuna products are detrimentally affected, such that it may be appropriate to unbundle the different elements and examine them in a sequential 
manner. However, we do not consider that an examination of the detrimental impact of the 
amended tuna measure could be properly conducted without also taking account of the interrelationship among those elements and addres sing the manner in which they operate together 
to modify the conditions of competitio n in the US market for tuna products. 
7.62.  We do not see that the Panel considered su ch interrelationship in its examination. Instead, 
the Panel conducted a segmented analysis for each of the "eligibility criteria"
369, the "different 
certification requirements"370, and the "different tracking and verification requirements".371 In 
setting out those separate analyses, the Panel took  the view that the type of detrimental impact 
caused by the sets of certification and tracking and verification requirements is of a "distinct" and "separate" nature from the detrimental impact caused by the eligibility criteria.
372 In particular, the 
Panel referred to Mexico's statement that the eligibility criteria "are responsible for the fact that 
most Mexican tuna products are ineligible to receive the label".373 Conversely, the Panel identified 
the nature of the detrimental impact flowing from the different certification requirements and from 
the different tracking and verification requirements as the "competitive advantage" that is 
accorded to tuna products derived from tuna caught outside the ETP large purse-seine fishery, in the form of the lesser costs and burdens that th e amended tuna measure imposes on such tuna 
products, as compared to those that it imposes on tuna products derived from tuna caught within 
the ETP large purse-seine fishery.
374 After having conducted these three segmented analyses, the 
Panel did not seek to synthesize them or to examine more holistically the implications that the combined operation of the different sets of requirements might have had for its analysis of the 
detrimental impact of the amended tuna measure on Mexican tuna products. 
7.63.  In our view, the Panel's analytical approach  overlooks that the detrimental impact resulting 
from the amended tuna measure cannot properly be examined through isolated analyses of the 
detrimental impact associated with discrete sets of requirements under that measure. Since all of 
the conditions for access to the dolphin-safe label may bear on such detrimental impact
375, a 
proper assessment of the detrimental impact of the amended tuna measure on Mexican tuna products calls for an examination of the manner in which the different labelling conditions under 
the measure operate together in a way that affect s the conditions of competition for Mexican tuna 
products in the US market.  
7.64.   We further recall that, as pointed out in paragraph 5.9 above, "Article 21.5 proceedings do 
not occur in isolation from the original proceedings"; rather, "both proceedings form part of a 
                                               
367 Original Panel Report, paras. 7.289 and 7.291. See also Panel Report, para. 7.424. 
368 See Original Panel Report, para. 7.317; and Appellate Body Report, US – Tuna II (Mexico) , 
para. 234. 
369 Panel Report, section 7.5.2.2.2. 
370 Panel Report, section 7.5.2.4.1. 
371 Panel Report, section 7.5.2.5.1. 
372 Panel Report, para. 7.105. (emphasis omitted) 
373 Panel Report, para. 7.105 (referring to Mexico's second written submission to the Panel, para. 117). 
374 Panel Report, para. 7.105. 
375 As the Panel itself recognized, the US dolphin-safe labelling regime necessarily includes not only the 
"substantive … requirement[s]", but al so the various certification and trac king and verification requirements 
constituting the mechanisms by which compliance with those substantive requirements is "monitored and demonstrated". (Panel Report, fn 125 to para. 7.37) WT/DS381/AB/RW 
 
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 continuum of events".376 A panel's examination of a measure taken to comply must take due 
account of the findings by the original pane l and the Appellate Body adopted by the DSB.377 Thus, 
for example, in setting out the analytical scope of its detrimental impact analysis, the panel in  US – COOL (Article 21.5 – Canada and Mexico)  stated that it would "follow the original panel's 
approach".
378 On that basis, the compliance panel assessed whether the measure taken to comply 
with the recommendations and rulings of the DSB modified the detrimental impact that was found to exist in the original proceedings.
379  
7.65.  Similarly, we believe that the analytical approach to detrimental impact employed by the 
original panel and the Appellate Body constitutes relevant background for a proper assessment of 
the detrimental impact of the amended tuna meas ure. Such an assessment might usefully build 
on, or take as its starting point, the Appellate Body's finding in the original proceedings that the 
detrimental impact of the original tuna measure was "caused by the fact that most Mexican tuna 
products contain tuna caught by setting on dolphins in the ETP and are therefore not eligible for a 'dolphin-safe' label", whereas "most tuna products from the United States and other countries that 
are sold in the US market contain tuna caught by other fishing methods outside the ETP and are 
therefore eligible for a 'dolphin-safe' label."
380 In the original proceedings, the original panel and 
the Appellate Body focused on access to the dolphin-safe label. In doing so, they grounded their 
assessments on the regulatory distinction whereby tuna products derived from tuna caught by 
setting on dolphins were disqualified from access to the dolphin-safe label, whereas tuna products derived from tuna caught by other fishing methods qualified for such label, which was the regulatory distinction at the core of Mexico's challenge.
381 At the same time, the Appellate Body 
acknowledged the interlinkages between the variou s elements of the US dolphin-safe labelling 
regime when it stated that the aspect of the or iginal tuna measure that caused the detrimental 
impact on Mexican tuna products was "the difference in  labelling conditions " for tuna products 
containing tuna caught by setting on dolphins, on the one hand, and for tuna products containing 
tuna caught by other fishing methods, on the other hand.382 
7.66.  Thus, it seems to us that the findings of detrimental impact by the original panel and the 
Appellate Body reinforce that a proper assessment of the detrimental impact of the amended tuna 
measure on Mexican tuna products calls for an examination of the manner in which the different labelling conditions under the measure operate toge ther. Such an analysis should also encompass 
consideration of whether these conditions operate in a way that produces the same, or that 
modifies, the detrimental impact that was found to exist in the original proceedings. For instance, 
the Panel could have explained the extent to which the certification and tracking and verification requirements introduced by the 2013 Final Rule for tuna products originating outside the ETP large 
purse-seine fishery had the effect of reducing (or increasing) access to the dolphin-safe label for 
                                               
376 Appellate Body Report, Chile – Price Band System (Article 21.5 – Argentina) , para. 136 (referring to 
Appellate Body Report, Mexico – Corn Syrup (Article 21.5 – US) , para. 121). See also Appellate Body Report, 
US – Upland Cotton (Article 21.5 – Brazil) , para. 386. 
377 Appellate Body Report, Chile – Price Band System (Article 21.5 – Argentina) , para. 136 (referring to 
Appellate Body Reports, US – Oil Country Tubular Goods Sunset Reviews (Article 21.5 – Argentina) , para. 142; 
Mexico – Corn Syrup (Article 21.5 – US) , para. 121; US – FSC (Article 21.5 – EC II) , para. 61; US – Softwood 
Lumber IV (Article 21.5 – Canada) , para. 68 and 77; and US – Softwood Lumber VI (Article 21.5 – Canada) , 
para. 102). 
378 Panel Reports, US – COOL (Article 21.5 – Canada and Mexico) , para. 7.66. 
379 Panel Reports, US – COOL (Article 21.5 – Canada and Mexico) , paras. 7.68-7.175. 
380 Appellate Body Report, US – Tuna II (Mexico) , para. 284. 
381 See Original Panel Report, para. 7.253; and Appellate Body Report, US – Tuna II (Mexico) , 
para. 284. 
382 Appellate Body Report, US – Tuna II (Mexico) , para. 284. (emphasis added) Elsewhere in its report, 
the Appellate Body noted the original panel's findings that, for tuna products originating outside the ETP large purse-seine fishery, no certifications were required that no dolphins  had been killed or seriously injured in the 
nets where the tuna was caught. (See ibid., para. 292 (referring to Original Panel Report, para. 7.561)) The 
Appellate Body also upheld the original  panel's finding that the imposition of a substantive requirement that no 
dolphins be killed or seriously injured outside the ETP woul d not be practically relevant "if it is assumed that it 
cannot be verified". (Ibid., para. 294 (quoting Original Panel Report, para. 7.541)) WT/DS381/AB/RW 
 
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 such tuna products.383 On that basis, the Panel could have examined whether the combined 
operation of the different labelling conditions under the amended tuna measure narrowed (or broadened) the detrimental impact of the regulatory differences in treatment of Mexican tuna products as compared to  like products of US or other origin, in terms of access to the dolphin-safe 
label. 
7.67.  We observe that, in setting out its analysis of the consistency with Article 2.1 of the 
"eligibility criteria", the Panel did recognize the importance of the findings made by the panel and 
the Appellate Body in the original proceedings.
384 However, in the remainder of its discussion of 
the eligibility criteria, the Panel limited itself to "respect[ing] and reaffirm[ing]" the Appellate Body's alleged finding that the regulatory  distinction between tuna products derived from 
tuna caught by setting on dolphins and tuna products derived from tuna caught by other fishing 
methods is "even-handed" and therefore "not inconsistent with Article 2.1".
385 In other words, the 
Panel did not refer to the Appellate Body's findings under the first step of the analysis of less 
favourable treatment, i.e. concerning the detrimental impact of this regulatory distinction. Nor did 
the Panel conduct its own assessment of whether the disqualification from the dolphin-safe label of 
tuna products derived from tuna caught by setting on dolphins, coupled with the qualification for the label of tuna products derived from tuna caug ht by other fishing method s, detrimentally affects 
the competitive opportunities of Mexican tuna products in the US market.
386 
7.68.  The Panel's approach is somewhat surprising given that both Mexico and the United States 
indicated to the Panel that, under the amended tuna measure, as under the original tuna measure, most Mexican tuna products are still being excluded from access to the dolphin-safe label, whereas 
most like products from the United States and other countries are still eligible for access to such 
label.
387 In this regard, it is not clear to us that, as the Panel contends, Mexico's position on 
detrimental impact "developed"388 over the course of the proceedings to encompass allegations of 
separate and distinct detrimental impact flowing from "the absence of sufficient fishing method 
qualification, record keeping, verification and observer requirements" outside the ETP large purse-seine fishery.
389 We further note that, on appeal, neither Mexico nor the United States 
considers that the Panel's analyses of the detrimental impact of the certification requirements and 
the tracking and verification requirements were  warranted or necessary given the findings of 
detrimental impact by the original panel and the Appellate Body. 
                                               
383 Given that only four months elapsed between the adoption of the 2013 Final Rule on 9 July 2013 and 
Mexico's initiation of these Article 21.5 proceedings on 15 November 2013, it may have been difficult for the parties to produce empirical evidence showing the chan ges in the levels or proportions of tuna products 
originating outside the ETP large purse-seine fishery that are able to access the dolphin-safe label. We note, nevertheless, that both part ies did adduce evidence regarding the levels of dolphin mortality and serious injury 
in fisheries other than the ETP large purse-seine fishery. The Panel mi ght have been able to rely on this 
evidence to draw some conclusions regarding the extent  to which the additional requirements in the amended 
tuna measure have disqualified from access to the dolphin- safe label tuna products that would have been able 
to access the label under the original tuna measure. 
384 Panel Report, para. 7.118. The Panel found it "appropriate" to "rely upon factual and legal 
conclusions made by the original pa nel and the Appellate Body, at least in the absence of compelling new 
evidence that would render those previous findings unsustainable". ( Ibid., para. 7.119) 
385 Panel Report, para. 7.126. We address this portion of the Panel's reasoning in more detail in 
section 7.2.3.2.2 of this Report. 
386 We note that, in the portion of its Report where it examined the consistency of the "eligibility criteria" 
with Articles I:1 and III:4 of the GA TT 1994, the Panel did consider that the regulatory distinction between 
tuna products derived from tuna caught by setting on do lphins and tuna products derived from tuna caught by 
other fishing methods "has th e effect of denying [Mexican] tuna products a valuable market advantage (that is, 
access to the dolphin-safe label)", thus modifying the conditions of competition to the detriment of such 
products. (Panel Report, para. 7.447. See also para. 7.498) The Panel, however, did not complement this finding with an assessment of the amount of tuna prod ucts from the United States and other countries that are 
excluded from access to the label by virtue of the new ce rtification and tracking and verification requirements 
in force outside the ETP large purse-seine fishery. 
387 Mexico's first written submission to the Panel, paras. 223-224; United States' first written submission 
to the Panel, para. 215. See also Panel Report, para. 7.446. 
388 Panel Report, paras. 7.102. 
389 Panel Report, paras. 7.104 (quoting Mexico's second written submission to the Panel, para. 117 
(emphasis omitted)). Indeed, as the Panel explicitly acknowledged, "the core" of Mexico's argumentation on 
detrimental impact is that, "under the amended tuna  measure, the majority of Mexican tuna and tuna 
products … is ineligible to receive the United States dolphin-safe label, while the majority of tuna and tuna 
products caught or manufactured by the United States and other WTO Members … are eligible." (Ibid., para. 7.152) WT/DS381/AB/RW 
 
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 7.69.  Having identified these general concerns regarding the Panel's segmented approach to 
detrimental impact, we now turn to consider the analytical approach that the Panel used in conducting its discrete analyses of detrimental im pact based on the costs and burdens associated 
with the certification requirements and the tracking and verification requirements.  
7.70.  The Panel considered that the certification and tracking and verification requirements "are 
relevant only to tuna eligible and intended to receive the dolphin-safe label" – that is, only to tuna not caught by setting on dolphins.
390 Accordingly, the Panel compared the costs and burdens that 
the different certification and tracking and verification requirements entail for, on the one hand, 
Mexican tuna products derived from tuna caught other  than by setting on dolphins , and, on the 
other hand, tuna products of US or other origin derived from tuna caught other  than by setting on 
dolphins .391 We recall that, for the purposes of both the original and these compliance proceedings, 
"Mexican tuna products are 'like' tuna products of United States' origin and tuna products 
originating in any other country"392, whether those products are, or are not, derived from tuna 
caught by setting on dolphins. Thus, by limiting its comparison to the treatment accorded to tuna 
products that are "eligible" for the dolphin-safe la bel, the Panel's analyses of the respective costs 
and burdens flowing from the different certificat ion and tracking and verification requirements 
focused on a subset  of the products found to be  "like" in this dispute. 
7.71.  In considering the propriety of the Panel's approach, we recall that the product scope for a 
detrimental impact comparison depends on the products that a panel has found to be "like" for the purposes of Article 2.1.
393 Once the "like" products have been properly identified, Article 2.1 
requires a panel to compare, on the one hand, the treatment accorded under the measure at issue 
to the "group" of like products imported from the complaining Member with, on the other hand, 
that accorded to the "group" of like domestic products and/or the "group" of like products 
originating in all other countries.394 This is not to say that a finding of detrimental impact requires 
that all products imported from the complaining Member be treated less favourably than all like 
domestic products and/or all like products originating in other countries. However, in our view, a 
panel may not artificially limit its analysis to only subsets of the relevant groups of like products in 
a manner that risks skewing the proper comparis on for purposes of determining detrimental 
impact.  
7.72.  We also note that, in assessing whether the original tuna measure had a detrimental impact 
on Mexican tuna products in the US market, the original panel and the Appellate Body compared 
the treatment accorded to the group of Mexican tuna  products with that accorded to the groups of 
like US products and like products from other countries, in order to assess the relative positions of these product groups in respect of access to the dolphin-safe label.
395 Given the particular 
characteristics of the amended tuna measure, and in the light of the facts and circumstances of 
this dispute, we consider that, in order to reach its conclusions on detrimental impact, the Panel was called upon to compare the treatment that the labelling conditions under the amended tuna 
measure accord to the group  of Mexican tuna products, on the one hand, with the treatment 
accorded to the groups  of like tuna products from the United States and other countries, on the 
other hand. Indeed, a proper identification of the product groups to be compared was germane to all the steps of the Panel's analysis under Article 2.1, including the assessment of whether the 
amended tuna measure modifies the conditions of  competition to the detriment of Mexican tuna 
                                               
390 Panel Report, para. 7.143. 
391 We recall that most Mexican tuna products deri ve from tuna caught in the ETP large purse-seine 
fishery, whereas most like products from the United States an d other countries derive from tuna caught in 
other fisheries. 
392 Appellate Body Report, US – Tuna II (Mexico) , para. 202. See also Panel Report, para. 7.71. 
393 See Appellate Body Report, US – Clove Cigarettes , para. 192. 
394 See Appellate Body Report, US – Clove Cigarettes , para. 193 (referring to Appellate Body Report,  
EC – Asbestos , para. 100). See also Appellate Body Reports, US – Tuna II (Mexico) , para. 215; and  
US – COOL , para. 268. 
395 See Original Panel Report, para. 7.295; and Appellate Body Report, US – Tuna II (Mexico) , 
paras. 234 and 284. WT/DS381/AB/RW 
 
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 products in the US market and, if so, whether such a detrimental impact stems exclusively from a 
legitimate regulatory distinction.396 
7.73.  This does not imply that the Panel's conclusions of detrimental impact had to rest on a 
finding that the certification and tracking and verification requirements impose additional costs and 
burdens on every  Mexican tuna product, or on the entire  group  of Mexican  tuna products, as 
compared to every  like product, or on the entirety of the groups of like products from the 
United States and other countries. Indeed, there may well be instances in which an examination of 
the treatment accorded to a portion of a relevant group of like products will suffice to support a 
finding that such a product group is detrimentally affected by the technical regulation at issue.397 
We note, however, that, elsewhere in its Report , the Panel referred to Mexico's statement that 
"most" Mexican tuna products are still excluded from access to the dolphin-safe label398 as 
"virtually all of Mexico's purse seine tuna fleet continues to fish in the ETP by setting on 
dolphins".399 These statements suggest that very few, if any, Mexican tuna products are "eligible" 
for the dolphin-safe label and therefore subject to  any additional costs and burdens flowing from 
the certification and tracking and verification requirements. The Panel did not explain why an 
analysis of the treatment that the amended tuna measure accords to this category of tuna products had explanatory force for, and could properly support, a finding that the group  of Mexican 
tuna products is detrimentally affected by the certification and tracking and verification 
requirements.
400 
7.74.   Accordingly, we have difficulty identifying the basis on which the Panel thought it 
appropriate to limit its analysis to a subset of the product groups that have been found to be "like" 
in this dispute. By focusing exclusively on the costs and burdens imposed by the certification and 
tracking and verification requirements on only "eligible" Mexican tuna products, the Panel artificially skewed the proper comparison for pu rposes of determining detrimental impact, rather 
than grounding its analysis on a full comparison of the relevant groups of like products in the light 
of the particular facts and circumstances of this dispute.  
7.75.  Based on the foregoing, we conclude that the Panel employed an incorrect analytical 
approach to assessing whether the amended tuna measure has a detrimental impact on Mexican 
tuna products in the US market. First, by underta king a segmented analysis of each of the three 
sets of requirements under the amended tuna me asure, the Panel failed to recognize and take 
account of the interlinkages between the disqualification of tuna products derived from tuna 
caught by setting on dolphins, on the one hand, and the certification and tracking and verification 
requirements, on the other hand, and to conduct a holistic assessment of how those various labelling conditions adversely affect the conditions of competition for Mexican tuna products in the 
US market as compared to like tuna products from the United States and other countries. Because 
it adopted such a segmented approach, the Panel failed to assess meaningfully the extent to which the detrimental impact that was found to exist in the original proceedings might have been altered 
by the changes introduced by the amended tuna measure. Second, in analysing the detrimental 
impact of the certification and tracking and ve rification requirements, the Panel engaged in a 
                                               
396 In our view, there may be circumstances in which an analysis of detrimental impact grounded on a 
comparison between inappropriate groups  of products might, in turn, prev ent a panel from properly conducting 
the second step of its analysis as to whether a measure accords less favourable treatment within the meaning of Article 2.1. 
397 For instance, in the original proceedings, the Appellate Body concluded that the fact that "most" 
Mexican tuna products were excluded from access to the do lphin-safe label sufficiently warranted a finding that 
the original tuna measure had a detrimental impact on the competitive opportunities of Mexican tuna products 
in the US market. (Appellate Body Report, US – Tuna II (Mexico) , paras. 234-235) In order to reach such a 
conclusion, the Appellate Body did not find it necessa ry to assess the treatment accorded by the original 
measure to every  Mexican tuna product as compared to every  like product of US or other origin. 
398 Panel Report, para. 7.105 (referring to Mexico's second written submission to the Panel, para. 117). 
399 Panel Report, para. 7.444 (quoting Mexico's first written submission to the Panel, para. 227). The 
United States, for its part, does not contest the Panel's reference to Mexico's argument and stresses that, in 
recent years, Mexico has not exported any tuna produc ts derived from tuna caught other than by setting on 
dolphins to the United States. (See United States' a ppellant's submission, paras. 176 and 329 (referring to 
Mexico's response to Panel question No. 57, paras. 146 and 155)). We note that the original panel found that, as of 2009, Mexican tuna products accounted for only 1% of the US market for imported tuna products, and an even smaller percentage of the total US market. (Original Panel Report, para. 7.355) 
400 We recall that, as the Appellate Body has cautione d, a panel should not "ascribe undue weight to the 
effect of a technical regulation in any hypoth etical scenario". (Appellate Body Reports, US – COOL 
(Article 21.5 – Canada and Mexico) , para. 5.16 (emphasis omitted)) WT/DS381/AB/RW 
 
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 comparison of the treatment accorded to subsets of the relevant groups of like products, instead of 
comparing the treatment accorded to the group  of Mexican tuna products with that accorded to 
the groups  of like products of US or other origin, without identifying a proper basis for doing so.  
7.76.  For the reasons set out above, we find that the Panel erred in its analysis of whether the 
amended tuna measure has a detrimental impact on Mexican tuna products in the US market 
within the meaning of Article 2.1 of the TBT Agreement. Having found error in the Panel's analysis, we do not consider it necessary to rule on the United States' claims on appeal that: (i) the Panel 
improperly made the case for Mexico by grounding its findings of detrimental impact with respect 
to the certification and tracking and verification requirements on the different costs and burdens imposed by such requirements on suppliers of tuna products operating inside and outside the 
ETP large purse-seine fishery
401; (ii) the Panel erred in finding a difference in costs and burdens 
stemming from the certification and tracking and verification requirements and in failing to explain 
how any such difference modifies the conditions of competition to the detriment of Mexican tuna products
402; and (iii) the Panel did not properly establish a genuine relationship between the 
certification and tracking and verification requirements and any detrimental impact on Mexico's 
competitive opportunities in the US market.403 
7.2.3  Less favourable treatment – Stems ex clusively from a legitimate regulatory 
distinction 
7.77.  The United States challenges the Panel's articulation of the legal test under Article 2.1 of the 
TBT Agreement for determining whether the detrimental impact on imported products stems exclusively from a legitimate regulatory distinction. In addition, the United States and Mexico each 
raises certain claims of error under the second step of the analysis of less favourable treatment in 
connection with the Panel's application of the law to the facts in its analysis of the eligibility criteria, the certification requirements, and the tr acking and verification requirements set out in 
the amended tuna measure. Before addressing the participants' claims with respect to the Panel's 
application of Article 2.1, we turn to analyse the United States' challenge to the Panel's articulation of the "treatment no less favourable" standard under Article 2.1 of the TBT Agreement. 
7.2.3.1  Whether the Panel erred in its interpre tation of Article 2.1 and its articulation of 
the legal standard for determining whether th e detrimental impact on imported products 
stems exclusively from a legiti mate regulatory distinction 
7.78.  The United States argues that the Panel erred in its understanding of Article 2.1 of the 
TBT Agreement and articulated an incorrect legal standard for determining whether the 
detrimental impact on imported products stems exclusively from a legitimate regulatory distinction.
404 In particular, the Panel wrongly indicated that the question in the second part of the 
analysis of less favourable treatment under Article 2.1 is "whether 'detrimental treatment is 
explained by, or at least reconcilable with, the objectives pursed by the measure at issue.'"405 The 
United States explains that "[t]he second step of the Article 2.1 analysis is not a single-factor test 
based on whether a 'rational connection' exists be tween the detrimental impact and the objectives 
of the measure but an analysis of whether the regulatory distinctions that account for the detrimental impact 'are designed an d applied in an even-handed manner.'"
406 In support of its 
position, the United States points to the Appella te Body's explanation that "the question for 
determining whether the 'detrimental impact stems exclusively from legitimate regulatory 
distinctions' is whether the regulatory distinctions that account for that detrimental impact 'are 
                                               
401 United States' appellant's submission, paras. 136-144 and 288-295. 
402 United States' appellant's submission, paras. 145-155 and 314-319. 
403 United States' appellant's submission, paras. 167-184 and 327-330. 
404 The United States puts forward this argument in challenging thr ee aspects of the Panel's analysis: 
(i) the Panel's finding that the certification requirements do not stem exclusively from a legitimate regulatory distinction; (ii) the Panel's finding that the determination provisions do not stem exclusively from a legitimate regulatory distinction; and (iii) the Panel's finding that the tracking and verification  requirements do not stem 
exclusively from a legitimate regulato ry distinction. Since all three challenges are premised on the same 
contention by the United States, we examine them toge ther. (United States' appellant's submission, paras. 25, 
36, 192, 257, 264, and 334) 
405 United States' appellant's submission, para. 192 (quoting Panel Report, para. 7.196). 
406 United States' appellant's submission, para. 36 (quoting  Appellate Body Reports, US – COOL 
(Article 21.5 – Canada and Mexico) , para. 5.92; and referring to  Appellate Body Reports, US – COOL , 
para. 271). WT/DS381/AB/RW 
 
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 designed and applied in an even-handed manner such that they may be considered "legitimate" for 
the purposes of Article 2.1.'"407 The United States adds that, in the context of this dispute, the 
Appellate Body has been clear that this question  should be answered through an assessment of 
whether the requirement "is even-handed in the manner in which it addresses the risks to dolphins 
arising from different fishing method s in different areas of the ocean."408 The United States accepts 
that the objectives of the measure, and an inquiry into whether the detrimental impact can be reconciled with those objectives, are not necessarily irrelevant to the analysis. For the 
United States, however, in this dispute, such considerations are relevant as part of the analysis of 
whether the regulatory distinction is "calibrated" to the risks to dolphins arising from different fishing methods in different areas of the oceans.
409 "Even-handedness" is the appropriate inquiry 
to determine whether the detrimental impact stems exclusively from legitimate regulatory 
distinction, and, in the United States' view, an inquiry into "calibration" is not a separate test from 
"even-handedness". Rather, the original proceedin gs show that the Appellate Body used the 
analytical tool of "calibration" in its application of the "even-handedness" standard. The 
United States adds that the Panel's analysis of the certification requirements, however, suggests 
that the Panel wrongly considered that the legal st andard under Article 2.1 prohibits an evaluation 
of different risks.  
7.79.  Mexico contends that "the question of whether the regulatory distinction that accounts for 
the detrimental impact is designed and applied in  an even-handed manner" and "the question of 
whether the detrimental impact caused by the re gulatory distinction can be explained by, or 
reconciled with, the objectives of the measur e at issue" are "not mutually exclusive".410 Rather, 
the latter question is a factor that may be relevant in resolving the first question. In particular, 
Mexico argues that the legal test under Article 2.1 of the TBT Agreement focuses on whether the 
detrimental impact on imports stems exclusively from a legitimate regulatory distinction, that is, 
whether the relevant regulatory distinction is "e ven-handed". This does not mean that all like 
products must always be treated identically, but rather that there must be a rational, objective, and non-discriminatory basis for distinguishing among products.
411 Thus, Mexico adds, the test for 
determining whether the application of a measure results in arbitrary or unjustifiable 
discrimination should focus on the cause of the discrimination, or the rationale put forward to explain its existence.
412 
7.80.  According to Mexico, the jurisprudence developed by the Appellate Body in interpreting 
Article 2.1 of the TBT Agreement and Article XX of the GATT 1994 does not include a "calibration" 
test.413 Rather, Mexico points out, the term "calibration" was introduced by the United States in 
the original proceedings when it argued that the original tuna measure was "calibrated" to the risk 
that dolphins may be killed or seriously injured when tuna was caught.414 Mexico further argues 
that the notion of "calibration" is not equivalent to the notions of "even-handedness" or "arbitrary or unjustifiable". In response to questioning at  the oral hearing, Mexico added that, even if 
"calibration" may be one way to assess whether a regulatory distinction involves arbitrary or 
unjustifiable discrimination, such an examination is not appropriate in the present dispute, in particular, given that the amended tuna measure does not incorporate or reflect any concept of "calibration". Mexico added that, in any event, an assessment into whether the measure at issue is 
"calibrated" must be done in the light of the design and architecture of the measure, as well as the 
circumstances surrounding the measure. 
7.81.  In order to assess the United States' claim on appeal, we first identify the test articulated by 
the Panel for assessing "treatment no less favourable" under Article 2.1 of the TBT Agreement. 
Then, we turn to analyse the central question raised in the United States' claim, namely, whether 
                                               
407 United States' appellant's submission, para. 192 (quoting Appellate Body Reports, US – COOL 
(Article 21.5 – Canada and Mexico) , para. 5.92). 
408 United States' appellant's submission, para. 192 (quoting Appellate Body Report, US – Tuna II 
(Mexico) , para. 232). 
409 United States' appellant's submission, para. 193 (referring to Appellate Body Report, US – Tuna II 
(Mexico) , para. 297). 
410 Mexico's appellee's submission, para. 125. 
411 Mexico's appellee's submission, para. 61. 
412 Mexico's appellee's submission, para. 62  (referring to Appellate Body Report, Brazil – Retreaded 
Tyres , para. 226). 
413 Mexico's appellee's submission, para. 60. 
414 Mexico's appellee's submission, para. 59  (referring to Appellate Body Report, US – Tuna II (Mexico) , 
para. 282). WT/DS381/AB/RW 
 
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 the test articulated by the Panel regarding the second step of the "treatment no less favourable" 
requirement under Article 2.1 reflects and is consistent with the proper legal standard under that provision, as identified by the Appellate Body. Our analysis in the present subsection is limited to assessing the Panel's interpretation and articulation of the legal standard. We address the issue of 
whether the Panel incorrectly applied  the legal test in the subsections that follow, which deal with 
the various claims of error raised by both the United States and Mexico in this regard. 
7.82.  In identifying the second step of the "treatment no less favourable" requirement under 
Article 2.1 of the TBT Agreement, the Panel recalled that, in line with Appellate Body 
jurisprudence, panels must examine whether the detrimental impact on imports stems exclusively 
from a legitimate regulatory distinction rather than reflects discrimination against the group of imported products.
415 The Panel stated that: 
… the Appellate Body has explained that an  analysis of whether detrimental impact 
stems exclusively from a legitimate regulatory distinction (or whether a technical regulation that causes detrimental impact is even handed) must take account of 
whether the technical regulation at issue is "applied in [a] manner that would 
constitute a means of arbitrary or unjustifiable discrimination between countries where the same conditions prevail or a disguised restriction on international trade".
416 
7.83.  The Panel highlighted the similarity betw een this language and that of the chapeau of 
Article XX of the GATT 1994, and posed the question  of whether this meant that panels should 
draw on the jurisprudence elaborated under the chap eau in interpreting and applying Article 2.1 of 
the TBT Agreement, noting that this issue was "highly contested by the parties".417 The Panel, 
first, indicated that it could not agree with the United States that the provisions set out in 
Article 2.1 and the chapeau of Article XX "are entirely different".418 In the Panel's view, the 
Appellate Body "has consistently instructed panels to look for 'arbitrary or unjustifiable 
discrimination' as one indication that a technical regulation provides less favourable treatment to 
imported products in contravention of TBT Article 2.1."419 The Panel considered that the 
Appellate Body thus "clearly intended that panels would apply the 'less favourable treatment' 
requirement in Article 2.1 of the TBT Agreement in light of the jurisprudence developed in the 
context of the chapeau of Article XX."420 The Panel also understood the Appellate Body's ruling in 
EC – Seal Products  to mean that, while the tests under Ar ticle 2.1 and the chapeau of Article XX 
are not identical and should not be conflated, there are nevertheless important similarities and 
overlaps between them, and thus that the Appella te Body jurisprudence developed in the context 
of one provision may be used to interpret similar concepts in the other.421 
7.84.  The Panel proceeded to make two further inte rpretative points. First, the Panel stated that, 
in considering whether detrimental impact caused by a technical regulation reflects "arbitrary 
discrimination", it could consider, inter alia , whether the detrimental treatment can be reconciled 
with, or is rationally related to, the policy pursue d by the measure at issue. In so doing, the Panel 
adopted a test of "arbitrary or unjustifiable discr imination" that has previously been used by the 
Appellate Body – for example, in EC – Seal Products  – to assess the conformity of a measure with 
the requirements of the chapeau of Article XX of the GATT 1994. In the Panel's view, even if the 
analysis under Article 2.1 may involve examination of more than just the existence or not of 
"arbitrary discrimination", using such an analysis to determine whether a technical regulation 
involves arbitrary discrimination "may help the Panel determine whether the detrimental impact 
                                               
415 Panel Report, para. 7.73 (referri ng to Appellate Body Report, US – Clove Cigarettes , para. 215). 
416 Panel Report, para. 7.79 (quoting  the sixth recital of the preamble of the TBT Agreement and 
referring to Appellate Body Report, US – Clove Cigarettes , para. 94). 
417 Panel Report, para. 7.80. 
418 Panel Report, paras. 7.83 and 7.87 (quoting United States' second written submission to the Panel, 
para. 84). 
419 Panel Report, para. 7.87 (referri ng to Appellate Body Reports, US – Clove Cigarettes , para. 173; and 
US – COOL , para. 268). 
420 Panel Report, para. 7.87. 
421 Panel Report, para. 7.90. The Pa nel further considered that the Appellate Body's approach in  
US – Clove Cigarettes  "closely resembles the type of analysis cond ucted under the chapeau of Article XX of the 
GATT 1994, and confirms that there are important similarities between the analysis under Article XX and the 
analysis under Article 2.1 of the TBT Agreement." (Ibi d., para. 7.92 (referring to  Appellate Body Report,  
US – Clove Cigarettes , para. 225)) WT/DS381/AB/RW 
 
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 complained of … stems exclusively from a legitimate regulatory distinction".422 Second, the Panel 
expressed its understanding that the concept of "even-handedness" is not a separate criterion 
required under Article 2.1, but rather "an analytical tool, a kind of rhetorical measure or test that deploys a fluid, broadly equitable concept as a proxy or gauge to help a panel determine whether 
identified detrimental treatment stems exclusivel y from a legitimate regulatory distinction".
423 For 
the Panel, determining whether a measure is even-handed can help to determine whether the identified detrimental treatment is fully explaina ble as a consequence of a legitimate regulatory 
distinction – in which case it could be said to stem exclusively  from that distinction – or whether 
the detrimental treatment, while perhaps connected to or broadly based on a legitimate regulatory 
distinction, is nevertheless not fully or precisely accounted for by the regulatory distinction that the responding Member seeks to pursue – in which case it could not be concluded that the detrimental 
treatment stems exclusively  from the distinction pursued.
424 The Panel also stated that it viewed 
the notion of even-handedness as directing a panel's attention to the "fit" or "fairness" of a technical regulation, and as broader than the concept of "arbitrary discrimination".
425  
7.85.  In sum, the Panel stated that, in determining whether the detrimental impact stems 
exclusively from a legitimate regulatory distinction, it could consider whether the detrimental treatment can be reconciled with, or is rationally related to, the objectives pursued by the measure 
at issue.
426 However, the Panel did not, as the United States suggests, indicate that this is a 
"single-factor test" that should always and exclusively be used for assessing whether detrimental impact stems exclusively from a legitimate regulatory distinction.
427 To the contrary, the Panel 
explicitly stated that such an analysis "may help" in determining whether the relevant distinction 
involves "arbitrary discrimination".428 The Panel further qualified the role of this inquiry by pointing 
out that examining whether a measure involves "arbitrary discrimination" is one way  of 
demonstrating that a measure is not even-handed,  but that ascertaining whether the detrimental 
impact stems exclusively from a legitimate regulatory distinction "may involve examination of 
more than just the existence (or not) or 'arbitrary discrimination'".429 
7.86.  Having described the relevant Panel findings, we turn to assess whether, as alleged by the 
United States, they amount to an erroneous articulation of the "treatment no less favourable" 
requirement under Article 2.1 of the TBT Agreement.  In our view, in challenging the Panel's finding 
that the relevant test under the second step of a "less favourable treatment" analysis may involve assessing whether the detrimental treatment can be reconciled with, or is rationally related to, the 
objectives pursued by the measure, the United States is also challenging the Panel's statement 
that the Appellate Body "clearly intended" for panels to apply the "treatment no less favourable" requirement in Article 2.1 in the light of the juri sprudence developed in the context of the chapeau 
of Article XX.
430 
7.87.  We begin by noting that, having posed the question as to how panels should undertake the 
second step of the "treatment no less favourable" analysis under Article 2.1 of TBT Agreement431, 
the Panel turned, in the very next paragraph of its Report, to the question of whether it could rely 
upon the jurisprudence relating to the chapeau of Article XX of the GATT 1994.432 In contrast, 
when seeking to ascertain the analysis required under Article 2.1, the Appellate Body has first looked to more immediate context for that provision.
433 As set out above, the Appellate Body has 
emphasized that the specific context provided by other provisions of the TBT Agreement – notably, 
Annex 1.1, Article 2.2, and the second, fifth, and sixth recitals of the preamble – is instructive in understanding the expression "treatment no less  favourable" under Article 2.1. This specific 
context "supports a reading that Article 2.1 does not operate to prohibit a priori  any restriction on 
                                               
422 Panel Report, para. 7.91. 
423 Panel Report, para. 7.93. 
424 Panel Report, para. 7.94. 
425 Panel Report, paras. 7.95-7.96. 
426 Panel Report, para. 7.91. 
427 United States' appellan t's submission, para. 36. 
428 Panel Report, para. 7.91. 
429 Panel Report, para. 7.91. See also para. 7.96. 
430 Panel Report, para. 7.87. 
431 Panel Report, para. 7.79. 
432 Panel Report, para. 7.80. 
433 Appellate Body Reports, US – Clove Cigarettes , para. 173; US – Tuna II (Mexico) , para. 213;  
US – COOL , para. 268; EC – Seal Products , para. 5.124. WT/DS381/AB/RW 
 
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 international trade".434 In particular, the sixth recital sheds light on the meaning and ambit of the 
"treatment no less favourable" requirement in Article 2.1 by making clear that technical regulations may pursue legitimate objectives, but must not be applied in a manner that would constitute a means of arbitrary or unjustifiable discrimination.
435 
7.88.  At the same time, given that the sixth recital of the preamble of the TBT Agreement serves 
as relevant context for understanding Article 2.1, and the language of that recital has important commonalities with the chapeau of Article XX of the GATT 1994, the jurisprudence under the 
chapeau of Article XX is not irrelevant to understanding the content of the second step of the 
"treatment no less favourable" requirement under Article 2.1 of the TBT Agreement. Indeed, previous Appellate Body decisions concerning one provision of a covered agreement may shed light on a proper understanding of the scope and meanin g of a different provision in another agreement 
where the same or similar language is used in both provisions
436, provided always that due 
account is taken of more immediate context, and of the function of each provision. 
7.89.  We recall that, in EC – Seal Products , the Appellate Body indicated that "there are important 
parallels between the analyses under Article 2.1 of the TBT Agreement and the chapeau of 
Article XX."437 Prominent among them is the fact that the concepts of "arbitrary or unjustifiable 
discrimination between countries where the same conditions prevail" and a "disguised restriction 
on trade" are found both in the chapeau of Article XX and in the sixth recital of the preamble of the 
TBT Agreement. Yet, "there are significant differ ences between the analyses under Article 2.1 of 
the TBT Agreement and the chapeau of Article XX of the GATT 1994"438, and the legal standards 
applicable under the two provisions differ.439 Article 2.1 imposes affirmative obligations on 
Members in respect of their technical regulations. By contrast, Article XX establishes exceptions to 
obligations under the GATT 1994, and the function of its chapeau "is to maintain a balance between a Member's right to invoke the exceptions  under the subparagraphs of Article XX and the 
substantive rights of the other Members under the various other provisions of the GATT 1994."
440 
7.90.  We can see that the Panel recognized both these similarities and differences. It noted, for 
example, the Appellate Body's statement that "imp ortant parallels" exist between the chapeau of 
Article XX and the "treatment no less favourable" requirement under Article 2.1. Moreover, the 
Panel explicitly acknowledged that, "while the test s in the chapeau of Article XX and Article 2.1 of 
the TBT Agreement overlap, they are not identical."441 In the Panel's view, "[w]hereas Article 2.1 
asks whether detrimental treatment stems from a legitimate regulatory distinction, and while the 
existence of 'arbitrary or unjustifiable discrimination' is one way in which inconsistency with this 
aspect of Article 2.1 of the TBT Agreement can be  shown, the chapeau of Article XX is focused 
                                               
434 Appellate Body Reports, US – COOL , para. 268. See also Appellate Body Reports, US – Clove 
Cigarettes , para. 172; and US – Tuna II (Mexico) , para. 212. 
435 Appellate Body Reports, US – Clove Cigarettes , para. 173; US – Tuna II (Mexico) , para. 213. The 
sixth recital of the preamble of the TBT Agreement recognizes that a WTO Member may take measures necessary for, inter alia , the protection of human, animal or plant lif e or health, of the environment, or for the 
prevention of deceptive practices, at the levels it cons iders appropriate, subject to the requirement that such 
measures "are not applied in a manner which would constitute a means of arbitrary or unjustifiable 
discrimination between countries where the same conditions prevail" or a "disguised restriction on international trade" and are "otherwise in accordance with the provisions of this Agreement". 
436 For instance, the Appellate Body has highlighted that, in view of the similarities between the 
language of Article XIV of the GATS and Article XX of the GATT 1994, previous decisions under each provision may be relevant in understanding the scope and me aning of the other. (Appellate Body Reports,  
US – Gambling , para. 291; China – Publications and Audiovisual Products , fn 452 to para. 239) 
437 Appellate Body Reports, EC – Seal Products , para. 5.310. 
438 Appellate Body Reports, EC – Seal Products , para. 5.311. 
439 The Appellate Body explained that: 
[u]nder Article 2.1 of the TBT Agreement, a panel has to examine whether the detrimental impact that a measure has on imported products  stems exclusively from a legitimate regulatory 
distinction rather than reflecting discrimination  against the group of imported products. Under 
the chapeau of Article XX, by contrast, the question is whether a measure is applied in a manner that would constitute a means of arbitrary  or unjustifiable discrimination  between countries 
where the same conditions prevail. 
(Appellate Body Reports, EC – Seal Products , para. 5.311 (emphasis original)) 
440 Appellate Body Reports, EC – Seal Products , para. 5.312 (referring to Appellate Body Report,  
US – Shrimp , para. 156). 
441 Panel Report, para. 7.89. WT/DS381/AB/RW 
 
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 solely  on whether a measure is applied in an arbitrarily or unjustifiably discriminatory manner (or 
is a disguised restriction on international trade)."442 
7.91.  These considerations suggest to us that, while the Panel jumped quickly to the chapeau of 
Article XX and certain jurisprudence relating to that provision in seeking guidance as to the proper 
legal test for the second step in the analysis of "treatment no less favourable" under Article 2.1 of 
the TBT Agreement, the Panel was not wrong to seek such guidance. Previous decisions under 
Article XX of the GATT 1994, particularly regarding the notion of "arbitrary or unjustifiable 
discrimination", may provide useful insight as to how the same concept should be understood in 
the context of the second step of the "treatment no less favourable" analysis under Article 2.1 of the TBT Agreement. 
7.92.  As regards the specific insight that the Panel drew from the jurisprudence under the 
chapeau of Article XX, we recall that, in the context of its analysis of Article XX, in EC – Seal 
Products , the Appellate Body stated that "[o]ne of the most important factors in the assessment of 
arbitrary or unjustifiable discrimination is the question of whether the discrimination can be 
reconciled with, or is rationally related to, the policy objective with respect to which the measure 
has been provisionally justified under one of the subparagraphs of Article XX."
443 This was the test 
adopted by the Panel for purposes of the second step of its "treatment no less favourable" analysis 
under Article 2.1 of the TBT Agreement, to which th e United States now objects. In the context of 
the chapeau of Article XX, the Appellate Body has explained that the reason why the assessment of whether discrimination is arbitrary or unjustifiable should be made in the light of the objective of the measure is that it is difficult to understand "how discrimination might be viewed as 
complying with the chapeau of Article XX when the alleged rationale for discriminating does not 
relate to the pursuit of or would go against the objective that was provisionally found to justify a measure under a paragraph of Article XX".
444 The same considerations, in our view, are valid in the 
context of the second step of the analysis of "treatment no less favourable" under Article 2.1 of 
the TBT Agreement. For the reasons set out above,  and in particular the reference in the sixth 
recital of the preamble of the TBT Agreement to "arbitrary and unjustifiable discrimination", the 
Panel's adoption of this test as part of its "treatment no less favourable" analysis does not, in 
itself, appear to us to be problematic. 
7.93.  Of course, in EC – Seal Products , the Appellate Body also noted that, depending on the 
nature of the measure at issue and the circumstances of the case at hand, additional factors – 
beyond the question of whether the discriminatio n can be reconciled with the policy objective – 
could also be relevant to the analysis of whether the discrimination is arbitrary or unjustifiable.445 
In a similar manner, the Panel expressly stated  that, in considering whether the detrimental 
impact caused by a technical regulation reflects arbitrary discrimination, it might "consider, among 
other things , whether the detrimental treatment can be reconciled with, or is rationally related to, 
the policy pursued by the measure at issue".446 Thus, the Panel correctly and explicitly recognized 
that merely inquiring into whether the detrimental impact of the amended tuna measure can be 
reconciled with the objectives of that measure might not, alone, be sufficient to ascertain whether the amended tuna measure discriminates against Mexican tuna products in an arbitrary or unjustifiable manner. In other words, and as alread y explained, the Panel did not characterize this 
legal test as a "single-factor test"
447, or as an exclusive means of assessing whether discrimination 
is arbitrary or unjustifiable. 
7.94.  In this connection, we further recall that one of the ways to determine whether the 
detrimental impacted caused by a technical re gulation is even-handed and therefore stems 
exclusively from a legitimate regulatory distinction is by examining whether the regulatory distinction is designed or applied in a manner that constitutes arbitrary or unjustifiable 
discrimination.
448 Therefore, as set out above, a measure that involves arbitrary or unjustifiable 
                                               
442 Panel Report, para. 7.89 (referri ng to Appellate Body Reports, EC – Seal Products , para. 5.311). 
(emphasis original) 
443 Appellate Body Reports, EC – Seal Products , para. 5.306 (referring to Appellate Body Reports,  
US – Shrimp , para. 165; and Brazil – Retreaded Tyres , paras. 227-228 and 232). 
444 Appellate Body Report, Brazil – Retreaded Tyres , para. 227. See also Appellate Body Reports,  
EC – Seal Products , para. 5.306. 
445 Appellate Body Reports, EC – Seal Products , para. 5.321. 
446 Panel Report, para. 7. 91. (emphasis added) 
447 United States' appellant's submission, paras. 36, 54, 416, and 432. 
448 Appellate Body Reports, US – COOL , para. 271. WT/DS381/AB/RW 
 
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 discrimination would not be designed or applied in an even-handed manner. At the same time, an 
examination of whether a measure is designed or applied in a manner that constitutes a means of arbitrary or unjustifiable discrimination is not  the only way to assess whether a measure lacks 
even-handedness. Similarly, the Panel explicitly acknowledged that an examination into arbitrary 
or unjustifiable discrimination is not the only means to determine whether a measure lacks even-
handedness.
449 
7.95.  As the above considerations show, a panel does not err by assessing whether the 
detrimental impact can be reconciled with, or is rationally related to, the policy pursued by the 
measure at issue, so long as, in doing so, it does not preclude consideration of other factors that may also be relevant to the analysis. In the present case, we do not see that the Panel's articulation  of the legal standard precluded such consideration.  
7.96.  Moreover, as indicated above, in determining whether the detrimental impact on imports 
stems exclusively from a legitimate regulatory distinction, a panel must carefully scrutinize whether the technical regulation at issue is even-handed in its "design, architecture, revealing 
structure, operation, and application" in the li ght of the "particular circumstances of the case".
450 
We note that the Panel correctly indicated that th e concept of "even-handedness" is not a separate 
criterion in the assessment of the second step of the "treatment no less favourable" requirement 
under Article 2.1; rather, "even-handedness" is the central concept for determining whether the 
identified detrimental treatment stems exclusiv ely from a legitimate regulatory distinction.451 In a 
situation where the detrimental impact caused by a technical regulation stems exclusively from a 
legitimate regulatory distinction, it must be concluded that such a technical regulation does not 
accord less favourable treatment to imported products and is therefore consistent with Article 2.1 
of the TBT Agreement. 
7.97.  With regard to the relationship between the notions of "even-handedness" and "arbitrary or 
unjustifiable discrimination", the Panel stated that, while "even-handedness" may overlap with the 
concept of "arbitrary discrimination", both terms are "conceptually distinct". For the Panel, while a showing of arbitrary discrimination is one way of demonstrating that a measure is not 
even-handed, the concept of "even-handedness", and the range of facts and circumstances that 
could lead a panel to find that a measure is not even-handed, is wider than those that could give 
rise to a finding of arbitrary discrimination.
452 In this regard, a regulatory distinction cannot be 
said to be designed and applied in an even-han ded manner if "it is designed or applied in a 
manner that constitutes a means of arbitrary or unjustifiable discrimination".453 While an 
examination of whether a technical regulation constitutes a means of arbitrary or unjustifiable discrimination and thus is not even-handed must be conducted in the light of the "particular 
circumstances of the case"
454, it is likely that this assessment involves consideration of the nexus 
between the regulatory distinctions found in the measure and the measure's policy objectives, including by examining whether the requirements imposed by the measure are disproportionate in 
the light of the objectives pursued.
455 
7.98.  At this juncture, we consider it important to recall that, in the original proceedings, the 
United States sought to explain that its measure was even-handed and that the detrimental impact did stem exclusively from a legitimate regulato ry distinction by introducing the notion of 
"calibration". In particular, the United States contended that its measure was even-handed 
because the distinctions that it drew between diffe rent tuna fishing methods and different areas of 
the oceans could be explained or justified by differences in the risks associated with such fishing 
methods and areas of the oceans. This, in turn, led the Appellate Body in the original proceedings 
to examine the legitimacy of the original measure's regulatory distinctions through the lens of the concept of "calibration" relied upon by the United  States. We emphasize that the Appellate Body's 
use of the terms "even-handed" and "calibrated" di d not constitute different legal tests, since the 
                                               
449 Panel Report, paras. 7.91 and 7.96. 
450 Appellate Body Report, US – Clove Cigarettes , para. 182. 
451 Panel Report, para. 7.93 (referri ng to Appellate Body Report, US – Clove Cigarettes , para. 215). 
452 Panel Report, para. 7.96. 
453 Appellate Body Reports, US – COOL , para. 271. 
454 Appellate Body Report, US – Clove Cigarettes , para. 182. 
455 For instance, we recall that, in US – COOL , the Appellate Body found the informational requirements 
imposed on upstream producers under the COOL measure to  be "disproportionate" as compared to the level of 
information communicated to consumers through the mandatory retail labels. (Appellate Body Reports,  US – COOL , para. 347) WT/DS381/AB/RW 
 
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 entire inquiry by the Appellate Body revolved around whether the United States had properly 
substantiated its argument that the original tuna measure was even-handed, and thus not inconsistent with Article 2.1, because it was "calibrated" to the risks to dolphins arising from different fishing methods in different areas of the oceans. 
7.99.  On the basis of the foregoing discussion, we find that the United States has not established 
that the Panel erred in recognizing the relevance of the concept of "arbitrary or unjustifiable 
discrimination" in the chapeau of Article XX of th e GATT 1994, or in identifying an examination of 
whether the detrimental treatment can be reconciled with, or is rationally related to, the measure's 
objectives as potentially "helpful" for purposes of the second step of the analysis of "treatment no less favourable" under Article 2.1 of the TBT Agreement. 
7.100.  At the same time, we also wish to express doubts about certain aspects of the Panel's 
articulation of the legal test for the "treatment no less favourable" requirement under Article 2.1 of 
the TBT Agreement. As noted, we find it some what odd that, after identifying the relevant 
interpretative question under Article 2.1, the Panel turned first to determine whether it could rely 
on the jurisprudence developed under Article XX of the GATT 1994, rather than turning to assess 
the jurisprudence on Article 2.1 itself, including the relevance of the sixth recital of the preamble of the TBT Agreement and the role of the "even-handedness" test.
456 Indeed, the Panel's 
discussion of the test of even-handedness is brief and is located at the very end of the subsection 
setting out its understanding of the legal test under Article 2.1 of the TBT Agreement.457 Moreover, 
albeit brief, many of the statements made by the Panel regarding its understanding of "even-handedness" are quite sweeping in nature.
458 
7.101.  It is also surprising that, in this part of  its reasoning, the Panel made little reference to the 
original Appellate Body report in this dispute459, and did not acknowledge or discuss the concept of 
"calibration" advanced by the United States, and us ed by the Appellate Body as a means of testing 
the even-handedness of the original tuna measure.460 In taking account of the United States' 
arguments, the concept of "calibration" was used by the Appellate Body in the original proceedings to assess compliance with Article 2.1. In these compliance proceedings, the United States has 
defended its dolphin-safe labelling regime from th e claim raised by Mexico under Article 2.1 of the 
TBT Agreement in terms similar to those that it used in the original proceedings. In the light of these considerations, as is explained in more detail below, there is a special relevance in these Article 21.5 proceedings in conducting an asse ssment of whether, under the amended tuna 
measure, the differences in labelling conditions fo r tuna products containing tuna caught by large 
purse-seine vessels in the ETP, on the one hand, and for tuna products containing tuna caught in other fisheries, on the other hand, are "calibrated" to the differences in the likelihood that dolphins 
will be adversely affected in the course of t una fishing operations by different vessels, using 
different fishing methods, in different areas of the oceans.  
7.102.  Having addressed the United States' challenge to the Panel's articulation  of the legal 
standard for the second step in an analysis of "treatment no less favourable" under Article 2.1 of 
the TBT Agreement, we examine below whether the Panel erred in its application  of this provision. 
In particular, we consider whether the Panel, having correctly recognized that the second step of the "treatment no less favourable" analysis is not focused solely  on "arbitrary or unjustifiable 
discrimination" and that "even-handedness" may call for an examination of other elements, took 
account of all the relevant elements in the particular circumstances of this case in assessing whether the amended tuna measure's detrimental impact on Mexican tuna products stems 
exclusively from a legitimate  regulatory distinction. 
                                               
456 Panel Report, paras. 7.79-7.80. 
457 Panel Report, section 7.5.1. 
458 For instance, the Panel stated that the term "' even-handedness' directs attention to what can 
perhaps best be called the 'fairness'  of a technical regulation. … Terms li ke 'fair' and 'just' are notoriously 
difficult to define a-contextually; accordingly, the spec ific criteria or indicia through which the fairness of a 
technical regulation should be assessed are not compre hensively enumerable in the abstract." (Panel Report, 
para. 7.96) 
459 We note, in particular, that, in the section addressing the legal test under Article 2.1 of the 
TBT Agreement, the Panel made only a few references to the Appellate Body report in the original proceedings 
in the footnotes to paragraphs 7.73-7.79 of its Report. 
460 The Panel did, nonetheless, express the view that, "even if a measure were based on  a legitimate 
regulatory distinction, the measure would nonetheless not stem exclusively  from that legitimate regulatory 
distinction if the detrimental impact  were disproportionate". (Panel Re port, para. 7.95 (emphasis original)) WT/DS381/AB/RW 
 
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 7.2.3.2  Whether the Panel erred in its asse ssment of whether the detrimental impact of 
the amended tuna measure on Mexican t una products stems exclusively from a 
legitimate regulatory distinction 
7.2.3.2.1  Preliminary observations 
7.103.  We begin by making certain preliminary observations regarding the analytical approach 
taken by the Panel in its assessment of whethe r the detrimental impact of the amended tuna 
measure on Mexican tuna products stems exclusively from a legitimate regulatory distinction. Our 
observations relate to several of the issues that we have already discussed in this Report. We 
consider, specifically: the Panel's segmented analytical approach; the test that it employed in assessing "even-handedness"; and the extent to which the analytical approach that it adopted relied upon, and took "due cognizance" of, the findings in the original proceedings that were 
adopted by, and became part of the recommendations and rulings of, the DSB. 
7.104.  As already explained, the Panel adopted a segmented approach and assessed the amended 
tuna measure on a "distinction-by-distinction basis".
461 Pursuant to this approach, the Panel 
separately considered the consistency of the following three sets of labelling conditions with 
Article 2.1 of the TBT Agreement: (i) the eligibility  criteria; (ii) the certification requirements; and 
(iii) the tracking and verification requirements. With respect to the eligibility criteria, the Panel did 
not itself conduct the two-step analysis required for assessing less favourable treatment under 
Article 2.1. Instead, the Panel relied upon the Appe llate Body's findings in the original proceedings, 
which it understood as having "settled" that the disqualification of all tuna products derived from tuna caught by setting on dolphins from access to the dolphin-safe label, while allowing those 
products derived from tuna caught by other fishing methods to qualify for such access, is 
"even-handed, and accordingly … not inconsistent with Article 2.1".
462 This meant, according to the 
Panel, that it had to examine "only the regulatory regime that currently applies to those  other 
fishing methods, which are qualified to catch dolphin-safe tuna".463 The Panel then proceeded, for 
each of the sets of certification and tracking and verification requirements, to conduct its own analysis of less favourable treatment. In the seco nd step of these analyses, the Panel found that 
the certification
464 and tracking and verification465 requirements are not even-handed and, 
therefore, cannot be said to stem exclusively from a legitimate regulatory distinction. Thus, the Panel found each of these two sets of requirements to be inconsistent with Article 2.1.
466 
7.105.  We have already expressed the view that , like the original tuna measure, the amended 
tuna measure has established a labelling regime comprised of various elements that work together 
towards the objectives pursued by the measure. We have also noted that, in discussing its jurisdiction under Article 21.5 of the DSU, the Pa nel itself emphasized the interlinkages between 
elements of the amended tuna measure, and stat ed that it would indicate and analyse these 
connections where relevant. We will examine below whether the Panel's segmented analysis of the even-handedness of each of the eligibility criteria , the certification requirements, and the tracking 
and verification requirements reflects and accounts for the manner in which the various elements 
of the amended tuna measure are interrelated. 
7.106.  We also recall that, in the preceding subsection of this Report, we found that the 
United States has not established that the Panel erred in recognizing the relevance of the concept 
of "arbitrary or unjustifiable discrimination" in the chapeau of Article XX of the GATT 1994, or in 
identifying an examination of whether the detrimental treatment can be reconciled with, or is 
                                               
461 Panel Report, para. 7.108. 
462 Panel Report, para. 7.126. See also paras. 7.127 and 8.2.a. 
463 Panel Report, para. 7.128. (emphasis original) The Panel also considered whether Mexico had 
submitted new evidence in these Article 21.5 proceedings  that would undermine the finding from the original 
proceedings that, in the view of the Panel, served as  the basis for the Appellate Body's determination that 
Article 2.1 of the TBT Agreement permits the United States to disqualify tuna caught by setting on dolphins from ever being labelled as dolphin-safe; namely, that no fishing method other than setting on dolphins has effects on dolphins as consistently  harmful as those caused by settin g on dolphins. (Ibid., para. 7.130 
(referring to Appellate Body Report, US – Tuna II (Mexico) , para. 289)) The Panel found "that Mexico ha[d] not 
provided evidence sufficient to demonstrate that settin g on dolphins does not cause observed and unobserved 
harms to dolphins, or that other tuna fishing methods consistently cause similar harms." (Ibid., para. 7.135) 
464 Panel Report, paras. 7.233 and 7.246. 
465 Panel Report, paras. 7.400 and 7.402. 
466 Panel Report, paras. 8.2.b and 8.2.c. WT/DS381/AB/RW 
 
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 rationally related to, the measure's objectives as potentially "helpful" for purposes of the second 
step of the analysis of "treatment no less favourable" under Article 2.1 of the TBT Agreement. The Panel did not use such an inquiry with respect to the eligibility criteria; rather, the Panel mainly relied on its understanding of the Appellate Body's analysis of the even-handedness of the original 
tuna measure. The Panel did, however, use such an inquiry in analysing the even-handedness of 
the different certification and tracking and verification requirements. At the outset of its consideration of the certification requirements, the Panel explicitly reiterated its view that, 
"in examining whether detrimental treatment stems exclusively from a legitimate regulatory 
distinction, a panel may take into account the extent to which the identified detrimental treatment is explained by, or at least reconcilable with, the objectives [pursued] by the measure at issue."
467 
The Panel was ultimately persuaded by Mexico that the different certification requirements are not 
even-handed because "captains may not necessarily and always have the technical skills required 
to certify that no dolphins were killed or seriou sly injured in a set or other gear deployment, and 
this may result in inaccurate information being passed to consumers, in contradiction with the 
objectives of the amended tuna measure."468 In analysing the different tracking and verification 
requirements, the Panel was persuaded that there is no rational or obvious connection between the amended tuna measure's imposition of a lighter burden on tuna caught outside the ETP large 
purse-seine fishery and the goals of the amended tuna measure
469, and found that none of the 
explanations provided by the United States suggested otherwise.470 This analysis supplied the 
basis for the Panel's finding that the tracking and verification "system currently in place under the amended tuna measure is not even-handed, and therefore does not stem exclusively from a 
legitimate regulatory distinction."
471  
7.107.  In both of these analyses, the Panel referre d, generally, to the "goals" or "objectives" of 
the amended tuna measure. Elsewhere in its Report472, the Panel identified these objectives to be 
twofold – ensuring that US consumers are not misled about the dolphin-safe status of their tuna 
products, and contributing to the protection of dolphins. We nevertheless note that, in assessing whether "a particular instance of detrimental treatment is reconcilable with or explicable by 
reference to the objectives" of the measure
473, the Panel's reasoning with respect to each of the 
sets of certification requirements, and tracking and verification requirements relies predominantly on the first of these objectives. Moreover, we have  already explained that the Panel identified this 
test as "a relevant consideration"
474 that may "help"475 to determine whether the distinctions 
drawn involve arbitrary discrimination, while also acknowledging that an inquiry into whether a 
distinction constitutes arbitrary or unjustifiable discrimination is not the only means to determine whether a measure lacks even-handedness such that  the detrimental treatment cannot be said to 
stem exclusively from a legitimate regulatory distinction.
476 Yet, we do not see that, in its analysis 
of the certification and tracking and verification requirements, the Panel took account of other considerations, employed additional tests, or analysed other dimensions (e.g. protection of 
dolphins from observed and unobserved harms)  of "even-handedness" before reaching its 
conclusions in respect of the certification and tracking and verification requirements. 
                                               
467 Panel Report, para. 7.196. 
468 Panel Report, para. 7.233. Pointing to the amended tuna measure's goal of "ensuring that consumers 
are not misled or deceived about whether tuna products contain tuna caught in a manner that adversely affects 
dolphins", Mexico argued that , because captain certification of the dolphi n-safe status of tuna is less reliable 
than observer certification, the amended tuna measure's sy stem of captain self-certification in respect of tuna 
caught outside the ETP large purse-seine fishery "d oes not bear a rational connection to", and is 
"entirely inconsistent" and "irreconcilable" with, such objective. (Ibid., para. 7.181 (quoting Mexico's second 
written submission to the Panel, paras. 3, 194, and 195)) 
469 Panel Report, para. 7.392. The Panel did not, in this part of its analysis, specifically identify to which 
objective(s) of the amended tuna measure it was re ferring. Nevertheless, the Pa nel's reference, in the 
preceding paragraph (para. 7.391), to Mexico's concerns about the greater likelihood that tuna caught in all fisheries other than the ETP large purs e-seine fishery will be incorrectly labelled as dolphin-safe, seems to 
suggest that it was referring to the goal of "ensuring that consumers are not misled or deceived about whether 
tuna products contain tuna caught in a manner that adversely affects dolphins". (Ibid., para. 7.181 (quoting Mexico's second written submission to the Panel, para. 3)) 
470 Panel Report, para. 7.400. 
471 Panel Report, para. 7.401. 
472 Panel Report, paras. 7.134 and 7.523. See also Appellate Body Report, US – Tuna II (Mexico) , 
paras. 242, 302, and 325. 
473 Panel Report, para. 7.390. 
474 Panel Report, para. 7.390. 
475 Panel Report, para. 7.91. 
476 Panel Report, paras. 7.91 and 7.93. WT/DS381/AB/RW 
 
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 7.108.  In this connection, as we have already explained, in the original proceedings, the 
United States defended the original tuna measure by arguing that it was "calibrated", that is, that the distinctions drawn between different tuna fishing methods and different areas of the oceans could be explained or justified by the differences in risk associated with such fishing methods and 
areas of the oceans.
477 This, in turn, led the Appellate Body to address the question of whether the 
original measure's detrimental impact on Mexican tuna products stemmed exclusively from a legitimate regulatory distinction by testing the "even-handedness" of the original tuna measure 
using the concept of "calibration". Ultimately, th e Appellate Body compared, on the one hand, the 
existence of risks to dolphins associated with the fishing method of setting on dolphins within the ETP, which were fully addressed by the labelling conditions under the original tuna measure with, on the other hand, the existence of risks of mortality or serious injury of dolphins in all fisheries 
other than the ETP large purse-seine fishery, wh ich were unaddressed, given the absence of any 
requirement under the original tuna measure to certify the dolphin-safe status in terms of mortality or serious injury of tuna caught outside the ETP by non-purse-seine vessels.
478 Having 
done so, the Appellate Body reached the conclusion that the United States had failed to show that 
its measure was "'calibrated' to the risks to dolphins arising from different fishing methods in different areas of the ocean", and thus that it had not demonstrated that the original tuna measure 
was even-handed "in the relevant respects".
479  
7.109.  With respect to the manner in which the ru les on the allocation of the burden of proof 
under Article 2.1 were applied in the original proceedings, we note that the Appellate Body considered first whether Mexico had made a prima facie  case establishing that the original tuna 
measure modifies competitive conditions to the detriment of Mexican tuna products and found that 
it had. It then proceeded to analyse whether that detrimental impact reflected discrimination or stemmed exclusively from a legitimate regulatory distinction. The Appellate Body stated in its 
Report that, although the burden of proof to show that the US dolphin-safe labelling provisions 
were inconsistent with Article 2.1 was on Mexico as the complainant, it was for the United States to support its assertion that its dolphin-safe labelling provisions were "calibrated" to the risks to 
dolphins arising from different fishing me thods in different areas of the oceans.
480 
7.110.  The Appellate Body recalled the reasons wh y the original panel was "not persuaded" that 
the United States had demonstrated that the re quirements of the US dolphin-safe labelling 
provisions were "calibrated", referring to key evidence presented, and key arguments 
substantiated, by the parties.481 The Appellate Body noted that the United States had presented 
"extensive evidence and arguments", and the orig inal panel made "uncontested findings, to the 
effect that the fishing method of setting on dolphins causes observed and unobserved adverse 
effects on dolphins."482 It also noted that the original panel appeared to have accepted the 
United States' argument that "the fishing technique of setting on dolphins is particularly harmful to dolphins."
483 While the original panel agreed with the Unit ed States that "certain fishing techniques 
seem to pose greater risks to dolphins than others"484, it was "not persuaded" that "at least some 
of the dolphin populations affected by fishing techniques other than setting on dolphins are not facing risks at least equivalent to those currently faced by dolphin populations in the ETP under AIDCP monitoring."
485 Referring to evidence and arguments submitted by Mexico, the original 
panel found that there were "clear indications that the use of certain tuna fishing techniques other  
                                               
477 Appellate Body Report, US – Tuna II (Mexico) , paras. 282-284. 
478 Appellate Body Report, US – Tuna II (Mexico) , paras. 292 and 296-297. The Appellate Body also 
referred to the original panel's findings that, with resp ect to purse-seine vessels fishing outside the ETP, the 
only requirement under the original tuna measure was to provide a captain's certification that there had been "no setting on dolphins" during the relevant trip. 
479 Appellate Body Report, US – Tuna II (Mexico) , para. 297. 
480 Appellate Body Report, US – Tuna II (Mexico) , para. 283. 
481 Appellate Body Report, US – Tuna II (Mexico) , para. 285 (quoting Original Panel Report, 
para. 7.559). 
482 Appellate Body Report, US – Tuna II (Mexico) , para. 287. 
483 Appellate Body Report, US – Tuna II (Mexico) , para. 289. 
484 Appellate Body Report, US – Tuna II (Mexico) , para. 288 (quoting Original Panel Report, 
para. 7.438). 
485 Appellate Body Report, US – Tuna II (Mexico) , para. 288 (quoting Original Panel Report, 
para. 7.617). WT/DS381/AB/RW 
 
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 than setting on dolphins may also cause harm to dolphins"486, and agreed with Mexico that risks 
from other fishing methods are not insignificant and do, under some circumstances, rise to the same level as the risk fr om setting on dolphins.  
7.111.  On the basis of these considerations, the Appellate Body concluded that "the United States 
ha[d] not demonstrated that the difference in labelling conditions [was] 'calibrated' to the risks to 
dolphins arising from different fishing methods in different areas of the ocean", that "the detrimental impact of the US measure on Mexica n tuna products stem[med] exclusively from a 
legitimate regulatory distinction," and that the measure was "even-handed in the relevant 
respects".
487 In the light of all the above, the Appellate  Body reached overall conclusions on what 
the participants had established, or failed to establish, under Article 2.1. It considered that Mexico had "established a prima facie  case that the US 'dolphin-safe' labelling provisions modif[ied] the 
conditions of competition in the US market to the detriment of Mexican tuna products and [were] 
not even-handed in the way in which they address[ed] the risks to dolphins arising from different fishing techniques in different areas of the ocean".
488 However, the Appellate Body considered that 
the United States had not "met its burden of rebutting this prima facie  case" because it had not 
"justified as non-discriminatory under Article 2.1 the different requirements … for access to the US 'dolphin-safe' label."
489 The Appellate Body thus concluded that the United States had not 
"demonstrated that the detrimental impact of  the US measure on Mexican tuna products 
stem[med] exclusively from a legitimate regulatory distinction."490 
7.112.  We reiterate that these Article 21.5 proceed ings form part of a continuum, such that due 
cognizance must be accorded to the recommendations and rulings made by the DSB in the original 
proceedings, based on the adopted findings of the Appellate Body and original panel.491 In their 
submissions to the Panel, both the United States and Mexico advanced arguments relating to the respective risks to dolphins associated with differ ent methods of fishing inside and outside the ETP. 
Mexico sought to establish that tuna fishing methods other than setting on dolphins have 
substantial adverse effects and that dolphins face risks of mortality or serious injury from tuna fishing outside the ETP that are equal to or greater than those posed to dolphins by fishing within 
the ETP.
492 For its part, the United States contended that the changes incorporated into the 
amended tuna measure through the 2013 Final Rule responded directly to the lack of calibration 
that the Appellate Body found to be responsible for the lack of even-handedness of the original 
tuna measure. In making its arguments, the United States relied on the findings from the original 
proceedings, as well as additional evidence, to establish that setting on dolphins in the ETP is 
"particularly harmful" to dolphins, and that the risks associated with such a tuna fishing method are greater than those associated with fishing methods that are not disqualified from access to the 
dolphin-safe label under the amended tuna measure.  
                                               
486 Appellate Body Report, US – Tuna II (Mexico) , para. 247 (quoting Original Panel Report, para. 7.520, 
in turn referring to National Marine Fisheries Service, An Annotated Bibliography of Available Literature 
Regarding Cetacean Interactions with Tuna Purse-Seine Fisheries Outside of the Eastern Tropical Pacific Ocean , 
Administrative Report LJ 96 20 (November 1996) (Original Panel Exhibit US-10), p. 38; and National Research Council, Dolphins and the Tuna Industry  (National Academy Press: Washington, D.C., 1992) (Original Panel 
Exhibit MEX-2), pp. 37 and 98 (emphasis original)). 
487 Appellate Body Report, US – Tuna II (Mexico) , para. 297. 
488 Appellate Body Report, US – Tuna II (Mexico) , para. 298. 
489 Appellate Body Report, US – Tuna II (Mexico) , para. 298. 
490 Appellate Body Report, US – Tuna II (Mexico) , para. 298. 
491 Appellate Body Report, Chile – Price Band System (Article 21.5 – Argentina) , para. 136 (referring to 
Appellate Body Reports, US – Oil Country Tubular Goods Sunset Reviews (Article 21.5 – Argentina) , para. 142; 
Mexico – Corn Syrup (Article 21.5 – US) , para. 121; US – FSC (Article 21.5 – EC II) , para. 61; US – Softwood 
Lumber IV (Article 21.5 – Canada) , paras. 68 and 77; and US – Softwood Lumber VI (Article 21.5 – Canada) , 
para. 102). 
492 Panel Report, paras. 7.111-7.112 (referring to Mexi co's second written submission to the Panel, 
paras. 248 and 263). Mexico did not advance these argume nts to show that the amended tuna measure is not 
"calibrated", but rather in support of its argument that th e qualification for "dolphin-saf e" status of tuna caught 
outside the ETP using such tuna fishing methods is inconsistent with the objectives of the amended tuna measure. Indeed, Mexico disputed the relevance of th e concept of "calibration" to the analysis of the 
even-handedness of the amended tuna measure. In Mexico's view, such concept is "inconsistent with the primary objective of the measure in question, which is co ncerned with the accuracy of  information provided to 
consumers." (Mexico's second written submission to th e Panel, para. 173) For Me xico, "[t]una is either 
dolphin-safe or it is not – eligibility for the dolphin- safe label cannot be viewed as a relative assessment." 
(Ibid.) WT/DS381/AB/RW 
 
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 7.113.  Having made these preliminary observations, and bearing them in mind, we proceed to 
examine the three separate parts of the Panel's analysis and findings in the light of the specific claims of error raised by the participants in this appeal.  
7.2.3.2.2  The eligibility criteria 
7.114.  Mexico argues that the Panel erred in its analysis of the eligibility criteria when assessing 
the consistency of the amended tuna measure with Article 2.1 of the TBT Agreement. In particular, 
Mexico contends that the Panel erred in finding that, in the original dispute, the Appellate Body 
"settled" the issue of even-handedness with re spect to the granting of eligibility for the 
dolphin-safe label to tuna products containing t una caught by fishing methods other than setting 
on dolphins.
493  
7.115.  Before addressing Mexico's claim of error on appeal, we describe the main findings by the 
Panel regarding the eligibility criteria in the amended tuna measure. 
7.2.3.2.2.1  The Panel's findings  7.116.  The Panel began by posing the question of  what, precisely, had been "definitively settled" 
by the Appellate Body in the original proceedings regarding the eligibility criteria.
494 For the Panel, 
it was "quite clear that the Appellate Body in th e original proceedings settled the question whether 
the United States can disqualify tuna caught by setting on dolphins from accessing the 
dolphin-safe label."495 In the Panel's view, "the Appellate Body clearly found that setting on 
dolphins causes observed and unobserved harm to dolphins."496 The Panel further explained its 
understanding that "what makes setting on dolphins particularly harmful is the fact that it causes certain unobserved effects  beyond  mortality and injury 'as a result of the chase itself'"
497, and 
emphasized that it was "precisely because these unobserved harms cannot be mitigated by 
measures to avoid killing and injuring dolphins that the original panel and the Appellate Body found that the United States is entitled to treat setting on dolphins differently from other fishing 
methods."
498 On this basis, the Panel "reaffirm[ed] the Appellate Body's finding that the 
United States is entitled, in pursuit of its desired level of protection, to disqualify tuna caught by that method from ever being labelled as dolphin-safe".
499 The Panel added that the original tuna 
measure was considered WTO-inconsistent, "not because it disqualified tuna caught by setting on 
dolphins from accessing the dolphin-safe label, but because the original tuna measure was not 
even-handed with respect to other methods of fishing  which may also cause harm to dolphins".500 
7.117.  Next, the Panel stated that, in the origin al proceedings, the Appellate Body answered the 
question of whether the failure of the US labelling regime to disqualify other  methods of tuna 
fishing necessarily deprived the original tuna me asure of even-handedness. In the Panel's view, 
the Appellate Body found that the disqualification of tuna caught by setting on dolphins, together 
with the qualification of tuna caught by other fishing methods, is not inconsistent with Article 2.1 
of the TBT Agreement. The Panel thus considered  this issue to be "settled" and proceeded to 
"reaffirm the finding of the Appellate Body that, to  the extent that they modify the conditions of 
competition in the US market to the detriment of Mexican tuna and tuna products, the eligibility 
                                               
493 Mexico's other appellant's submission, para. 91 (referring to Panel Report, paras. 7.117-7.135). 
494 Panel Report, para. 7.119. 
495 Panel Report, para. 7.120. 
496 Panel Report, para. 7.122. 
497 Panel Report, para. 7.122 (quoting Original Panel Report, para. 7.504). (emphasis original) 
498 Panel Report, para. 7.122. 
499 Panel Report, para. 7.123. 
500 Panel Report, para. 7.123. (emphasis original) WT/DS381/AB/RW 
 
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 criteria are even-handed, and accordingly are not inconsistent with Article 2.1 of the 
TBT Agreement".501 
7.2.3.2.2.2  Whether the Panel erred by misrea ding the findings of the Appellate Body in 
the original proceedings 
7.118.  Mexico asserts that the Panel erred in finding that the Appellate Body had already "settled" 
in the original dispute the issue of "even-handedness" concerning the granting of eligibility for the dolphin-safe label to tuna products containing tuna caught by fishing methods other than 
setting on dolphins. Mexico stresses that the analysis of even-handedness under Article 2.1 of the 
TBT Agreement "is complicated both legally and fa ctually" and that the Appellate Body did not 
undertake the "rigorous assessment" required to assess the even-handedness of the granting of 
the eligibility for the dolphin-safe label to tuna products containing tuna caught by other fishing 
methods.
502 Nor, according to Mexico, did the Appellate Body make the findings of even-
handedness or consistency with Article 2.1 that the Panel imputed to it.503 Rather, in Mexico's 
view, the findings of the Appellate Body related to the issue of disqualification of tuna caught by 
setting on dolphins from accessing the dolphin-safe label and did not address the granting of 
the dolphin-safe label to tuna products containing tuna caught by other fishing methods.504 
Therefore, Mexico emphasizes that this issue was not "definitively settled".505 
7.119.  The United States responds that, contrary to Mexico's assertions, the Panel correctly 
concluded that the Appellate Body had already rejected that the United States could not distinguish between different fishing methods consis tently with Article 2.1 of the TBT Agreement. 
The United States contends that Mexico wrongly argues that the Appellate Body's 
"even-handedness" analysis was limited to the disqualification of tuna caught by setting on 
dolphins and did not cover the eligibility of tuna caught by other fishing methods. According to the United States, that issue was "squarely before"
506 the Appellate Body in the original proceedings. 
Therefore, the United States asserts that the Panel did not err in finding that the issue was 
"definitively settled" in the original proceedings, given that the central question for the Appellate Body was whether the challenged measure was "calibrated" to the risks to dolphins 
arising from different fishing methods in different areas of the oceans.
507 
7.120.  To address this claim of error by Mexico, we must first recall the main findings made by 
the Appellate Body in the original dispute. 
7.121.  Having found that the original tuna measure modified the conditions of competition in the 
US market to the detriment of Mexican products, the Appellate Body turned to assess whether the 
detrimental impact reflected discrimination and, in particular, whether the measure at issue was "calibrated" to the risks to dolphins. The Appellate Body began by noting that the United States 
had argued before the original panel that, "to the extent that there are any differences in criteria 
that must be satisfied in order to substantiate 'dolphin-safe' claims, they are 'calibrated' to the risk that dolphins may be killed or seriously injured when tuna is caught".
508 The Appellate Body 
pointed out that "[t]he aspect of the measure that causes the detrimental impact on Mexican tuna 
products is thus the difference in labelling conditio ns for tuna products containing tuna caught by 
setting on dolphins in the ETP, on the one hand, and for tuna products containing tuna caught by other fishing methods outside the ETP, on the other hand."
509 Therefore, the Appellate Body 
                                               
501 Panel Report, para. 7.126. The Panel noted that the Appellate Body ultimately found that the original 
tuna measure was inconsistent with Ar ticle 2.1. However, according to the Panel, such finding was not because 
the United States disqualified tuna caught by setting on dolphins from accessing the dolphin-safe label, but 
rather because the regulatory regime imposed by  the United States on  tuna fishing methods other  than setting 
on dolphins did not sufficiently address the risks pose d to dolphins by those me thods. (Ibid., para. 7.127 
(referring to Appellate Body Report, US – Tuna II (Mexico) , para. 298)) The Panel then went on to examine a 
range of exhibits that both parties had referred to in the course of arguing about this issue and indicated that 
the new evidence presented in these Article 21.5 proceedings "merely supports the conclusion reached by the panel and the Appellate Body in the orig inal proceedings". (Ibid., para. 7.135) 
502 Mexico's other appellan t's submission, para. 93. 
503 Mexico's other appellan t's submission, para. 92. 
504 Mexico's other appellan t's submission, para. 90. 
505 Mexico's other appellant's submission, pa ra. 93 (quoting Panel Report, para. 7.119). 
506 United States' appellee's submis sion, para. 63. (emphasis omitted) 
507 United States' appellee's submission, para. 64. 
508 Appellate Body Report, US – Tuna II (Mexico) , para. 282. (fn omitted) 
509 Appellate Body Report, US – Tuna II (Mexico) , para. 284. WT/DS381/AB/RW 
 
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 considered that the question before it was whether the United States had demonstrated "that this 
difference in labelling conditions is a legitimate regulatory distinction, and hence whether the detrimental impact of the measure stem[med] exclusively from such a distinction rather than reflecting discrimination."
510 
7.122.  In addressing this question, the Appellate Body recalled and relied upon a number of 
findings made by the original panel. These included: that "the fishing method of setting on dolphins causes observed and unobserved adverse effects on dolphins"
511; that "these adverse 
effects [were] fully addressed in the measure at issue"512; and that "the use of certain tuna fishing 
techniques other than setting on dolphins may also cause harm to dolphins'."513 The 
Appellate Body highlighted that, while the origin al panel "accepted the United States' argument 
that the fishing technique of setting on dolphins is particularly harmful to dolphins", it "did not 
agree with the United States … that the risks to dolphins from other fishing techniques are 
insignificant and do not under some circumstances rise to the same level as the risks from setting on dolphins."
514 In the view of the Appellate Body, these findings formed the basis for the original 
panel's concerns about the way in which the original tuna measure addressed the potential 
adverse effects on dolphins from the use of fishing techniques other than setting on dolphins outside the ETP.
515 Like the original panel, the Appellate Body concluded that the original tuna 
measure did not address adverse effects on dolphins resulting from the use of fishing methods 
predominantly employed by fishing fleets supplyi ng the United States' and other countries' tuna 
producers, because there was no requirement for certification that no dolphins had been killed or seriously injured applicable to fisheries outside the ETP.
516 Rather, the only requirement that the 
original tuna measure applied to vessels fishing outside the ETP was, in respect of tuna caught by 
purse-seine vessels, to provide a certification by the captain that setting on dolphins had not taken 
place. The Appellate Body agreed with the origin al panel that this requirement did not address 
risks to dolphins resulting from fishing methods other than setting on dolphins.517 
7.123.  For these reasons, the Appellate Body concluded that "the United States ha[d] not 
demonstrated that the difference in labelling conditions for tuna products containing tuna caught 
by setting on dolphins in the ETP, on the one hand, and for tuna products containing tuna caught 
by other fishing methods outside the ETP, on the other hand, [was] 'calibrated' to the risks to dolphins arising from different fishing methods in different areas of the ocean."
518 Consequently, 
the Appellate Body considered that the United States had not rebutted Mexico's prima facie case 
that "the US 'dolphin-safe' labelling provisions modify the conditions of competition in the 
US market to the detriment of Mexican tuna products and are not even-handed in the way in which they address the risks to dolphins arising fr om different fishing techniques in different areas 
of the ocean."
519 
7.124.  As can be seen from the above, the Appellate Body did not make the findings attributed to 
it by the Panel. Although the Panel stated that it was "reaffirm[ing]" the Appellate Body's findings, 
the Appellate Body report contains no statement that the United States is "entitled" to disqualify 
tuna caught by setting on dolphins "from ever being labelled as dolphin-safe", much less that "the eligibility criteria are even-handed, and accordingly are not inconsistent with Article 2.1 of the TBT Agreement".
520 Indeed, the Panel does not refer to any paragraph(s) in the Appellate Body 
                                               
510 Appellate Body Report, US – Tuna II (Mexico) , para. 284. (emphasis original) The Appellate Body 
stated that it would examine to what extent the panel' s findings shed light on the question of "whether the 
difference in labelling conditions for tu na products containing tuna caught by setting on dolphins in the ETP, on 
the one hand, and for tuna products containing tuna ca ught by other fishing method s outside the ETP, on the 
other hand, [were] calibrated to the likelihood that dolp hins would be adversely affect ed in the course of tuna 
fishing operations in the respective conditions". (Ibid., para. 286) 
511 Appellate Body Report, US – Tuna II (Mexico) , para. 287. 
512 Appellate Body Report, US – Tuna II (Mexico) , para. 287. 
513 Appellate Body Report, US – Tuna II (Mexico) , para. 288 (quoting Original Panel Report, para. 7.520 
(emphasis original; fn omitted)). 
514 Appellate Body Report, US – Tuna II (Mexico) , para. 289. (fns omitted) 
515 Appellate Body Report, US – Tuna II (Mexico) , para. 289. 
516 Appellate Body Report, US – Tuna II (Mexico) , para. 289 (referring to Original Panel Report, 
para. 7.532). 
517 Appellate Body Report, US – Tuna II (Mexico) , para. 292 (referring to Original Panel Report, 
para. 7.561). 
518 Appellate Body Report, US – Tuna II (Mexico) , para. 297. 
519 Appellate Body Report, US – Tuna II (Mexico) , para. 298. 
520 Panel Report, paras. 7.123 and 7.126. WT/DS381/AB/RW 
 
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 report that contain these alleged findings. Im portantly, and as the Panel acknowledged, the 
Appellate Body found the original tuna measure to lack even-handedness and, for that reason, to 
be inconsistent  with Article 2.1 of the TBT Agreement.521  
7.125.  As we have already explained, and as the term itself implies, "even-handedness" is a 
relational concept, and must be tested through a comparative analysis. Regulatory distinctions by 
definition treat groups of products differently . Thus, the even-handedness of a measure and a 
regulatory distinction drawn thereunder cannot prop erly be appreciated through an examination of 
how they treat a single group of products or production methods. Rather, it is only through 
scrutiny of the treatment accorded to all the gr oups that are being compared that a proper 
assessment of even-handedness can be made.  
7.126.  In some parts of its reasoning, the Pa nel seemed to be aware of the relational and 
comparative nature of the analysis of whether the amended measure is calibrated and 
even-handed. The Panel noted that, in the origin al proceedings, the Appellate Body's finding of 
inconsistency with Article 2.1 was made not because the United States disqualified tuna caught by 
setting on dolphins from accessing the dolphin-safe label, but rather because the regulatory 
regime imposed by the United States on tuna fishing methods other  than setting on dolphins did 
not sufficiently address the risks posed to dolphins by those methods.522 H o w e v e r ,  i t  d o e s  n o t  
follow from the Appellate Body's findings in the original dispute that the measure's 
"disqualification" of products containing tuna caught in the ETP by setting on dolphins could be – or was – assessed for consistency with Article 2.1 in isolation from the requirements applied with respect to other fishing methods that also cause harm to dolphins in other fisheries. As noted, in 
order to assess whether the regulatory distinctions drawn under a measure are even-handed, the 
treatment of both groups between which the measure's regulatory treatment differs has to be appreciated. Whether a regulatory distinction that involves a denial of access to the dolphin-safe 
label in respect of setting on dolphins is even-handed depends not only on how the risks 
associated with this method of fishing are addresse d, but also on whether the risks associated with 
other fishing methods in other fisheries are addres sed, commensurately with their respective risk 
profiles, in the labelling conditions that apply in respect of tuna caught in such other fisheries. By 
finding that the issue of disqualifying setting on dolphins had been "settled" in the original proceedings, the Panel precluded a proper relation al and comparative analysis of the regulatory 
distinctions and the treatment of both groups of products (i.e. those that are ineligible for access 
to the label under the amended measure and those that are eligible for such access).  
7.127.  The same is true when, as was the case with the changes introduced to the dolphin-safe 
labelling regime through the measure taken to comply (the 2013 Final Rule), a measure is 
modified in a way that affects the treatment of only one of the two groups subject to that 
distinction. Following such modification, the ev en-handedness of the re gulatory treatment and 
relevant distinctions must be assessed anew. The legal significance of  the changed treatment 
afforded to one group of products cannot proper ly be understood by examining that group in 
isolation. Rather, answering the question of wh ether the detrimental impact stems exclusively 
from a legitimate regulatory distinction also requires consideration of the unchanged regulatory treatment accorded to the other group.  
7.128.  To us, the Panel's statements are all the more surprising given that they do not seem 
entirely consonant with the way in which the Panel itself described the findings of the Appellate Body in an earlier section of the Panel Re port. As explained in section 7.1 of this Report, 
in considering the scope of its jurisdiction, the Panel stressed that the Appellate Body "did not say 
that any one particular element" of the dolphin-safe labelling regime was "solely responsible" for the original tuna measure's lack of even-handedness.
523 The Panel observed that "[i]t is true that 
the Appellate Body's reasoning focused primarily on the disqualification of tuna caught by setting 
on dolphins from accessing the dolphin-safe label", but added that this "may very well have been a 
consequence of the way the case was argued by the parties".524 In any event, the Panel explained, 
                                               
521 Panel Report, para. 7.127 (referring to Appellate Body Report, US – Tuna II (Mexico) , para. 298). 
522 Panel Report, para. 7.127 (referring to Appellate Body Report, US – Tuna II (Mexico) , para. 298). As 
we have noted, the Panel found that the original tuna  measure was considered WTO-inconsistent, not because 
it disqualified tuna caught by setting on dolphins from accessing the dolphin-safe label, but because the 
measure was not even-handed with respec t to other methods of fishing , which may also cause harm to 
dolphins. (Ibid., para. 7.123) 
523 Panel Report, para. 7.33. 
524 Panel Report, para. 7.38. WT/DS381/AB/RW 
 
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 it was "the tuna measure as a whole, with its varying regulatory requirements, that was found [by 
the Appellate Body] to be inconsistent with Article 2.1 of the TBT Agreement."525 In particular, the 
Panel considered that the Appellate Body's referenc e in the plural to "the difference in labelling 
conditions" and "different requirements" indicated that the Appellate Body's findings encompassed 
various distinctions embedded in the original tuna measure, including in respect of the 
requirements pertaining to certification and tracking and verification.526  
7.129.  We do not see how, in the light of the Ap pellate Body's findings, the Panel formed the view 
that the Appellate Body report in the original proc eedings had "settled": (i) that the United States 
can disqualify tuna caught by setting on dolphins from ever accessing the dolphin-safe label527; 
and (ii) the question whether the disqualification of tuna caught by setting on dolphins, together with the qualification of tuna caught by other fishing methods, is inconsistent with Article 2.1 of 
the TBT Agreement.
528 In particular, the Appellate Body did not assess the questions identified by 
the Panel independently from each other. Nor does the Appellate Body report either state or imply that these issues had been "settled", especially in the categorical manner in which the Panel 
described them. Rather, in assessing whether the measure at issue was "calibrated", the 
Appellate Body scrutinized and compared the difference in labelling conditions for tuna products containing tuna caught by setting on dolphins in the ETP, on the one hand, and for tuna products 
containing tuna caught by other fishing methods ou tside the ETP, on the other hand. Therefore, it 
is only through an examination of the treatment accorded to both of the groups that are being 
compared that a proper assessment of the even-h andedness of the measure at issue can be made. 
7.130.  We further observe that the Panel's decision , in addressing the eligibility criteria under the 
amended tuna measure, to focus on the aspects that it considered the Appellate Body had already 
"settled" appeared to prevent it from engaging in a full exploration of the central question in these 
compliance proceedings, namely, whether the changes introduced by the United States through 
the amended tuna measure suffice to bring that measure into compliance with the 
recommendations and rulings of the DSB concerning Article 2.1 of the TBT Agreement.  
7.131.  In sum, the Appellate Body report contains  no finding that the United States is entitled 
"to disqualify tuna caught by that method from ever being labelled as dolphin-safe"
529, or that the 
original proceedings "settled the question whether th e disqualification of tuna caught by setting on 
dolphins, together with the qualification of tuna caught by other fishing methods, is inconsistent with Article 2.1 of the TBT Agreement."
530 Accordingly, the Panel's "reaffirm[ation]" of the 
supposed "finding" of the Appellate Body that "the eligibility criteria are even-handed, and 
accordingly are not inconsistent with Article 2.1 of the TBT Agreement", is incorrect.531 For the 
foregoing reasons, we find that the Panel erred in finding that the Appellate Body "settled" the 
issue of the even-handedness of the eligibi lity criteria in the original proceedings. 
7.2.3.2.3  The certification and tracki ng and verification requirements  
7.132.  The United States claims that the Panel erred in reaching findings that the detrimental 
impact caused by the certification requirements, and the tracking and verification requirements, 
does not stem exclusively from a legitimate regulatory distinction. As a result of these alleged errors, the United States seeks reversal of the Panel's ultimate findings that: (i) the certification requirements accord less favourable treatment to Mexican tuna products than that accorded to like 
products from the United States and to like products originating in any other country, in violation 
of Article 2.1 of the TBT Agreement; and (ii) the tr acking and verification requirements accord less 
favourable treatment to Mexican tuna products than that accorded to like products from the 
                                               
525 Panel Report, para. 7.33. See also para. 7.117.  The Panel also considered and rejected the 
United States' contention that the compliance proceedings should be limited to evaluating the 2013 Final Rule. The Panel concluded that its task was to determine whether the amended tuna measure, including the 2013 Final Rule, brings the United States into compliance  with the WTO covered agreements. (Ibid., para. 7.24) 
526 Panel Report, paras. 7.35-7.37 (q uoting Appellate Body Report, US – Tuna II (Mexico) , paras. 284 
and 298, respectively). 
527 Panel Report, para. 7.123. 
528 Panel Report, para. 7.126. 
529 Panel Report, para. 7.123. 
530 Panel Report, para. 7.126. 
531 Panel Report, para. 7.126. WT/DS381/AB/RW 
 
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 United States and to like products originating in any other country, in violation of Article 2.1 of the 
TBT Agreement.532  
7.133.  The United States appeals two main aspects of the Panel's assessment of the 
even-handedness of the certification requirements. First, the United States submits that the Panel 
erred in finding that the different certification requirements lack even-handedness because 
captains may not necessarily and always have the technical skills to certify that no dolphins were killed or seriously injured, and this may result in inaccurate information being passed to 
consumers, in contradiction with the objectives of the amended tuna measure. Second, the 
United States argues that the Panel erred in finding that the determination provisions prove that the detrimental impact caused by the certificatio n requirements does not stem exclusively from a 
legitimate regulatory distinction.
533 We address the United States' challenge to the Panel's analysis 
of the determination provisions in the next subsection of this Report. Following that subsection, we 
deal with claims raised by the participants under Article 11 of the DSU in connection with the Panel's analysis of the even-handedness of the different certification requirements.  
7.134.  In this subsection of our Report, we addres s the claims of error raised by the United States 
in respect of the first part of the Panel's an alysis of the even-handedness of the different 
certification requirements, and in respect of the Panel's analysis of the even-handedness of the 
different tracking and verification requirements. We begin by providing a summary of the relevant 
Panel findings, first with respect to the even-hande dness of the different certification requirements 
and, second, with respect to the different tracking and verification requirements.  
7.2.3.2.3.1  The Panel's findings 
The different certification requirements 
7.135.  With respect to the different certification requirements, Mexico submitted to the Panel that, 
like the original tuna measure, the amended tuna measure lacks even-handedness, because it fully 
addresses the risks posed to dolphins by setting on dolphins in the ETP, but does not fully address 
the risk posed by other fishing methods in other fisheries. Mexico highlighted that, within the ETP large purse-seine fishery, the required certifications must be provided both by the captain of the 
vessel and by an independent on-board observer, but,  outside that fishery, the certifications need 
be provided only by the captain. The Panel ex pressed the view that Mexico's claim that the 
different certification requirements are not even-handed rested on the "fundamental factual premise" that captains' certifications are "inherently unreliable" and "meaningless"
534 for two main 
reasons: (i) captains have a financial incentive to certify that their catch is "dolphin safe" even 
when it is not, and the amended tuna measure co ntains no mechanism to check this incentive; 
and (ii) captains lack the technical expertise necessary to certify accurately that no dolphins were 
killed or seriously injured, and therefore their certifications do not ensure that tuna labelled as 
"dolphin safe" in fact meet the statutory and regulatory requirements. 
7.136.  In considering the first of these assertions, the Panel was of the view that "the fact that 
many domestic, regional, and international regimes rely on captains' self-certification raises a 
strong presumption that, from a systemic perspective, such certifications are reliable."535 The 
Panel considered that the arguments and evidence submitted by Mexico were not sufficient to rebut this presumption
536, and noted that the United States' alternative understanding of the 
economic incentives facing captains seemed equally plausible.537 The Panel was thus not convinced 
                                               
532 United States' appellant's submission, paras. 135, 188, 194, 287, and 335 (referring to Panel Report, 
paras. 8.2.a and 8.2.b). 
533 United States' appellant's submission, para. 787. 
534 Panel Report, para. 7.198 (quoting Mexico's firs t written submission to the Panel, paras. 285 
and 295). 
535 Panel Report, para. 7.208. 
536 Panel Report, para. 7.209. 
537 Panel Report, para. 7.210. The United States argued before the Panel that, contrary to Mexico's 
position, vessel captains have economic incentives not to lie on their dolphin-safe declarations, because 
canneries would stop doing business with them and beca use of possible civil and criminal penalties. (Ibid., 
para. 7.202) WT/DS381/AB/RW 
 
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 that relying on captains' certifications outside the ETP large purse-seine fishery deprives the 
amended tuna measure of even-handedness.538 
7.137.  Next, in assessing Mexico's argument that captains may not have the necessary technical 
expertise to certify accurately that no dolphins were killed or seriously injured, the Panel 
considered it useful to compare the kinds of task s expected to be carried out by observers in the 
ETP and other oceans with those that are customarily carried out by captains.539 Having examined 
the evidence concerning the kinds of tasks perfor med by observers, the Panel concluded that this 
evidence "strongly suggests that certifying whether a dolphin has been killed or seriously injured in 
a set or other gear deployment is a highly complex task."540 Next, the Panel analysed the evidence 
regarding the tasks generally expected of captains and was not convinced that certifying dolphin mortality or serious injury is the kind of task generally expected of captains, or that captains 
necessarily have the skills to certify whether dolphins have been killed or seriously injured.
541 For 
these reasons, the Panel held that "the United States ha[d] not rebutted Mexico's showing that 
captains may not necessarily and always have the technical skills required to certify that no 
dolphins were killed or seriously injured in a set or other gear deployment"542, because "the 
United States ha[d] not explained why its measure assumes that captains have at their disposal the skills necessary to ensure accurate certification."
543 Accordingly, the Panel reasoned that 
captain certification of the dolphin-safe status of tuna "may result in inaccurate information being 
passed to consumers, in contradiction with the objectives of the amended tuna measure".544 The 
Panel therefore found that "the different certification requirements are not even-handed, and so cannot be said to stem exclusively from a legitimate regulatory distinction."
545 
7.138.  Subsequently, the Panel set out to "sketch" how it would analyse the even-handedness of 
the certification requirements if the United States , rather than Mexico, bore the burden of proof 
with respect to the second step of the anal ysis of "treatment no less favourable" under 
Article 2.1.546 The Panel accepted the United States' argument that "the 100 per cent observer 
requirement in the ETP is intricately tied to the sp ecial and, in some senses, 'unique' nature of the 
harms that the ETP large purse seine fishery poses to dolphins."547 In doing so, the Panel clarified 
that it did not understand the United States to have taken the position that such observer 
certifications are required in the ETP large purse-seine fishery but not in other fisheries "because the risk of dolphin mortality or serious injury is somehow less important in other fisheries".
548 
Rather, according to the Panel, the United States explained the different certification requirements 
as due to "the nature of the fishing technique used by ETP large purse seiners, which essentially 
involves the chasing and encirclement of many do lphins over an extended period of time, [and 
that this] means that it is necessary to have one single person on board with the responsibility of 
keeping track of those dolphins caught up in the chase and/or the purse seine nets set."549 In 
contrast, because the nature and degree of the interaction between dolphins and tuna fishers using other fishing methods in other oceans is "different in quantitative and qualitative terms 
(since dolphins are not set on intentionally, and interaction is only accidental), there is no need to 
have a single person on board whose sole task is to monitor the safety of dolphins during the set or other gear deployment".
550  
7.139.  The Panel considered that Mexico's evidence was not sufficient to rebut the United States' 
argument that the special and unique risks to dolphins posed in the ETP large purse-seine fishery 
justify the different certification requirements applied to the ETP large purse-seine fishery and other fisheries.
551 On this basis, the Panel observed that it "would find that the United States ha[d] 
made a prima facie  case that the different certification requirements stem exclusively from a 
                                               
538 Panel Report, para. 7.211. 
539 Panel Report, para. 7.213. 
540 Panel Report, para. 7.218. 
541 Panel Report, para. 7.225. 
542 Panel Report, para. 7.233. 
543 Panel Report, para. 7.234. 
544 Panel Report, para. 7.233. 
545 Panel Report, para. 7.233. 
546 Panel Report, paras. 7.235-7.236. 
547 Panel Report, para. 7.238. 
548 Panel Report, para. 7.240. 
549 Panel Report, para. 7.240. 
550 Panel Report, para. 7.240. (fns omitted) 
551 Panel Report, para. 7.241. WT/DS381/AB/RW 
 
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 legitimate regulatory distinction".552 However, the Panel then pointed out that, since the 
United States had not rebutted the evidence submitted by Mexico concerning the complexity of certifying the dolphin-safe status of a tuna catch, it "would find that the United States ha[d] not explained sufficiently why it assumes that captains  are capable of carrying out an activity that the 
amended tuna measure itself recognizes as highly complex and for which training and education 
are required".
553 In the absence of such explanation, the Panel felt "compelled" to find that, while 
the United States may legitimately draw distinctions between the ETP large purse-seine fishery 
and other fisheries, the lack of explanation concerning the technical capacities of captains means 
that the different certification requirements canno t be said to be even-handed, and as such to 
stem exclusively  from a legitimate regulatory distinction.554 One of the panelists was unable to 
agree with the reasoning and conclusions of the Panel's majority.555 
The different tracking and verification requirements 
7.140.  In assessing the even-handedness of the di fferent tracking and verification requirements, 
the Panel began its analysis by recalling that it was for Mexico to show  prima facie  that the 
different tracking and verification requirements are not even-handed.556 Then, the Panel expressed 
its agreement with Mexico's argument that "there is no obvious connection between the imposition of a lighter burden on tuna caught outside the ETP large purse-seine fishery and the goals of the 
amended tuna measure."
557 The Panel found that Mexico had shown prima facie  "that there is no 
rational connection between the different burden created by the tracking and verification requirements and the objectives of the amended tuna measure."
558 
7.141.  The Panel disagreed with the arguments pu t forward by the United States to rebut this 
showing. First, the Panel considered that the United States' argument that the tracking and 
verification requirements are origin neutral was not responsive to the point that the differences in the requirements are inconsistent with the objectives pursued by the amended tuna measure.
559 
Second, the Panel disagreed with the United States' argument that the tracking and verification 
requirements simply reflect international commitments undertaken by the United States and Mexico under the AIDCP, because this does not explain why the amended tuna measure contains a 
regulatory distinction whose effect is to impose a significantly lighter compliance burden on tuna 
caught in some fisheries than on tuna caught in others.
560  
7.142.  The Panel also did not accept the United States' explanation that the tracking and 
verification requirements are different because of  the higher degree of risk to dolphins in the 
ETP large purse-seine fishery. This higher risk "does not explain why the tracking and verification 
requirements, which by their very nature concern the movement of fish subsequent to the time of 
catch , differ between fisheries to the detriment of like Mexican tuna and tuna products".561 For the 
Panel, the different risk profiles of different fisheries may explain regulatory differences concerning 
                                               
552 Panel Report, para. 7.245. 
553 Panel Report, para. 7.246. 
554 Panel Report, para. 7.246. 
555 This panelist did not join in the analysis of th e Panel majority as set out in paragraphs 7.233-7.246 
of the Panel Report. Instead, in a se parate opinion, this panelist expr essed the view that any detrimental 
treatment caused by the diffe rent certification requiremen ts does stem exclusively from a legitimate regulatory 
distinction, and accordingly is not in consistent with Article 2.1 of the TBT Agreement. Since neither captain nor 
observer certifications are capable of detecting every  instance of dolphin mortality or serious injury, a certain 
degree or margin of error is necessar ily tolerated. This panelist emphasized that, provided that the tolerated 
margin of error is "calibrated" to the risks faced by do lphins in a particular fishery, the mere fact that the 
detection mechanisms inside the ETP large purse-seine fishery and outside that fishery are not the same does not deprive the amended tuna measure of even-handedness.  In this panelist's view, the United States had put 
forward evidence sufficient to show that the risks in a ll fisheries other than the ETP large purse-seine fishery 
are, as a general matter, significantly less serious than those posed in the ETP large purse-seine fishery. (See Panel Report, paras. 7.264-7.283) 
556 Panel Report, para. 7.389. The Panel also recalled th at the extent to which a particular instance of 
detrimental treatment is reconcilable with, or explic able by, reference to the objectives pursued by a 
challenged measure may be a relevant consideration in the assessment of whether that detrimental treatment 
stems exclusively from a legitimate regulatory distinction. (Ibid., para. 7.390) 
557 Panel Report, para. 7.392. 
558 Panel Report, para. 7.392. 
559 Panel Report, paras. 7.394-7.395. 
560 Panel Report, paras. 7.396-7.397. 
561 Panel Report, para. 7.398. (emphasis original) WT/DS381/AB/RW 
 
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 the eligibility criteria for fishing methods, as well as the need for an independent observer to 
monitor and certify during and immediately following the fishing activity itself , but they do not 
explain the different tracking and verification requirements, since such requirements apply only after the tuna has been caught. Finally, while the Pane l agreed that the United States is free to 
pursue its objectives at a level it considers appropriate, the Panel pointed out that this principle "is 
not a licence to modify the conditions of competition in a market to the detriment of imported products where such modification does not stem exclusively from a legitimate regulatory 
distinction".
562 
7.143.  For these reasons, the Panel found that the United States had not rebutted Mexico's 
prima facie  showing that the different tracking and verification requirements do not stem 
exclusively from a legitimate regulatory distinct ion, and therefore found that these requirements 
accord less favourable treatment to Mexican tuna products, in contravention of Article 2.1 of the 
TBT Agreement.563  
7.2.3.2.3.2  Whether the Panel erred by failing to examine whether the different 
certification and tracking and verification re quirements are "calibrated" to the risks to 
dolphins arising from different fishing me thods in different areas of the oceans  
7.144.  The United States argues that the Panel erred and applied an incorrect legal standard in 
failing to consider whether the different sets of certification and tracking and verification 
requirements are each "calibrated" to the risks to dolphins arising from diffe rent fishing methods in 
different areas of the oceans.564 The United States highlights that, in contrast, the panelist who 
wrote a separate opinion on one part of the certification requirements correctly recognized that the 
issue of calibration is determinative, and that "the analysis of whether the [different] requirements 
are calibrated to the differing risk profiles of the different fisheries lay 'at the very heart of the even-handedness analysis [] in this case.'"
565 In the United States' view, unlike the Panel 
majority's analysis of the certification requirements and the Panel's analysis of the tracking and 
verification requirements, the analysis by the panelist who wrote a separate opinion is consistent with the Appellate Body's guidance in the original proceedings.
566 
7.145.  The United States considers that the "central question" for the Appellate Body was whether 
the relevant regulatory distinction was "even-handed in the manner in which it addresse[d] the risks to dolphins arising from different fishing methods in different areas of the ocean."
567 
Moreover, the United States indicates that it relied on the Appellate Body's "calibration" analysis in 
designing its measure taken to comply with the DSB's recommendations and rulings. The 
United States adds that, apart from the opinion of the panelist who wrote a separate opinion, the Panel "erred in not similarly taking the Appellate Body's guidance [on calibration] into account".
568 
The United States also highlights that, even in  the original proceedings, the Appellate Body's 
"calibration" analysis also related to  the certification requirements themselves. In particular, the 
Appellate Body noted that an observer requiremen t "may be appropriate in circumstances in which 
                                               
562 Panel Report, para. 7.399. 
563 Panel Report, para. 7.400. Having made its finding that the different tracking and verification 
requirements under the amended tuna measure are not even-handed, and therefore do not stem exclusively 
from a legitimate regulatory distinction, the Panel indicated that it would reach the same conclusion if the burden of proof were to be allocated to the United Stat es. In such scenario, the Pane l explained, it would find 
that the United States had not made a prima facie  case that the different tracking and verification 
requirements stem exclusively from a legitimate regulatory distinction.  (Ibid., para. 7.402) 
564 United States' appellant's submission, paras. 196 and 334. 
565 United States' appellant's submission, para. 198 (quoting Panel Report, para. 7.276). See also 
United States' appellant's submission, para. 340. 
566 The United States, in particular, refers to the fo llowing reasons by the panelist who wrote a separate 
opinion: 
[T]he general rule that captains' certifications are sufficient outside the ETP large purse seine fishery while observers are required inside the ETP large purse seine fishery is even-handed. I think that this distinction represents a fair resp onse to the different risk profiles existing in 
different fisheries, as esta blished by the evidence.  
(United States' appellant's submission, pa ra. 204 (quoting Panel Report, para. 7.282)) 
567 United States' appellant's submission, para. 340 (quoting Appellate Body Report, US – Tuna II 
(Mexico) , para. 232). See also ibid., para. 200. 
568 United States' appellant's submission, para. 205. (fn omitted) WT/DS381/AB/RW 
 
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 dolphins face higher risks of mortality or serious injury".569 Thus, for the United States, the 
Appellate Body has already accepted the "critical principle" that "a WTO Member is not required to impose the same  requirements for all Members – but may impose different requirements to 
address different risks".
570  
7.146.  The United States points out, in this regard, that the Panel "did, in fact, conclude that the 
ETP large purse seine fishery has a different 'risk profile' for dolphin harm than other fisheries 
do".571 According to the United States, it is thus entirely appropriate to set different requirements 
for tuna produced in the ETP large purse-seine fishery than for tuna produced in other fisheries.572 
Therefore, "the fact that the [requirements applicable to the ETP large purse-seine fishery and all other fisheries] are different – and  may have different rates of accura cy – cannot, standing alone, 
be a basis on which to find that the difference in the regimes is not even-handed where the risk 
profiles between the ETP large purse seine fisher y and all other fisheries are so dramatically 
different."
573 The United States adds that the differ ences in the applicable requirements are 
"calibrated" to the risks to dolphins arising from different fishing methods in different areas of the 
oceans.574 
7.147.  Furthermore, with respect to the tracking and verification requirements, the United States 
disagrees with the Panel that a "calibration" analysis is not legally relevant to whether the 
regulatory distinction is even-handed because such  requirements apply after the tuna has already 
been caught. The United States argues that, for purposes of the "calibration" analysis, it is immaterial when any degree of inaccuracy is introduced into the system (i.e. at the initial designation of the set as dolphin safe or non-dolphin safe, or in the subsequent tracking of the 
tuna). For the United States, the fact that there is so much more tuna harvested where a dolphin 
has been killed or seriously injured in one fishery compared to other fisheries provides a basis for treating that fishery differently.
575 Consequently, the United States submits that the tracking and 
verification requirements of the amended tuna measure are consistent with Article 2.1 of the 
TBT Agreement. 
7.148.  Mexico makes three main arguments in response. First, Mexico disagrees that "calibrated" 
is equivalent to "even-handed" or "not arbitrary or unjustifiable", and disputes that the 
Appellate Body jurisprudence on Article 2.1 includes  a "calibration test". Second, Mexico contends 
that the amended tuna measure does not incorporate any concept of "calibration". Third, Mexico disagrees that there are relevant differences between the ETP and other ocean regions that could 
justify any regulatory distinctions in the certification requirements and the tracking and verification 
requirements.
576 Mexico argues that the Panel correctly concluded that the different certification 
requirements and the different tracking and ve rification requirements evidence a lack of 
even-handedness, such that the detrimental im pact caused by the amended tuna measure's 
different labelling conditions cannot be said to stem exclusively from a legitimate regulatory distinction. 
7.149.  Mexico argues that it cannot be even-h anded for the amended tuna measure to permit a 
higher proportion of incorrect dolphin-safe information with respect to tuna caught in allegedly low-risk fisheries outside the ETP than for tuna caught in the allegedly high-risk ETP large purse-seine fishery. Thus, the "calibration" that th e United States proposes is clearly arbitrary, 
unjustifiable, and lacking in even-handedness because it results in inaccurate and misleading 
information, in direct contradiction with the measure's objectives.
577 
7.150.  With respect to the different certification requirements, Mexico asserts that the Panel 
correctly found that they lack even-handedness because captains may not necessarily always have 
the technical skills required for accurate dolphin-safe certification. Since, according to Mexico, the 
                                               
569 United States' appellant's submission, para. 201 (quoting Appellate Body Report, US – Tuna II 
(Mexico) , fn 612 to para. 296). 
570 United States' appellant's submission, para. 202. (emphasis original) 
571 United States' appellant's submission, paras. 197 and 338 (referring to Panel Report, 
paras. 7.240-7.242, 7.278, and 7.398). 
572 United States' appellant's submission, para. 339. 
573 United States' appellant's submission, para. 341. (emphasis original) 
574 United States' appellant's submission, para. 342. 
575 United States' appellant's submission, para. 344. 
576 Mexico's appellee's submission, para. 58. 
577 Mexico's appellee's submission, para. 175. WT/DS381/AB/RW 
 
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 United States does not disagree that captain certifications are less accurate than AIDCP-approved 
observer certifications, "[i]t is therefore uncontested that requiring only captains' certifications for tuna caught outside the ETP large purse seine fishery results in a 'margin of error', meaning that at least some tuna products containing non-dolphin-safe tuna caught outside the ETP are being 
incorrectly labelled as dolphin safe in the U.S. market."
578 Since, in Mexico's view, the amended 
tuna measure's objective of "ensuring that cons umers are not misled or deceived about whether 
tuna products contain tuna caught in a manner that adversely affects dolphins" is "absolute", it 
follows that this difference in the certification requirements is "arbitrary, unjustifiable and lacking 
in even-handedness".579  
7.151.  Mexico also disagrees with the United States' argument that the different tracking and 
verification requirements are even-handed because they are "calibrated" to the risks to dolphins 
posed by different fishing methods in different fi sheries. Mexico highlights that, as the Panel 
properly found, the risk profile of harm to dolphins is no longer a relevant consideration after the tuna has been harvested and stored aboard a fishing vessel. Therefore, in Mexico's view, there is 
no nexus between the different tracking and verifi cation requirements and the allegedly different 
risk profiles of harm to dolphins from different fishing methods in different areas of the oceans.
580 
Mexico also rejects the United States' position that, "[f]or purposes of the calibration analysis, it is 
immaterial when  any degree of inaccuracy is introduced into the system".581  
7.152.  In our view, these claims of error by the United States raise several issues. The first issue 
t h a t  w e  h a v e  t o  e x a m i n e  i s  w h e t h e r ,  i n  a p p l y i ng the second step of the "treatment no less 
favourable" requirement under Article 2.1 of the TBT Agreement, the Panel was required to assess 
whether the certification and tracking and verifica tion requirements in the amended tuna measure 
are "calibrated" to the risks to dolphins arising from different fishing methods in different areas of the oceans. If the Panel was required to do so, a related issue is whether the Panel in fact 
undertook such an analysis. In addressing these issues, we also need to give consideration to the 
questions of whether the even-handedness of each set of requirements could properly be assessed 
separately and in isolation from the other elem ents of the amended tuna measure and, if so, 
whether the appropriateness or nature of the a pproach adopted in order to assess such even-
handedness would differ as between the different elements of the amended tuna measure. 
7.153.  We have already undertaken some analysis relevant to the first issue when we addressed 
the United States' appeal of the Panel's articulation of the legal standard to be applied in the 
second step of an assessment of whether a technical regulation accords less favourable treatment 
under Article 2.1 of the TBT Agreement. We note d that, in determining whether the detrimental 
impact on imports stems exclusively from a legitimate regulatory distinction, the "particular 
circumstances" of the case may inform the approp riate way in which to assess even-handedness in 
that specific case. While acknowledging the potential utility to the even-handedness assessment of an inquiry into whether the detrimental impact, and the explanations given for it, can be reconciled 
with, or are rationally related to, the policy purs ued by the measure at issue, we explained that 
this is one possible examination that could be undertaken to determine whether a regulatory distinction is arbitrary or unjustifiable and thus not even-handed under Article 2.1. Yet, taking too 
narrow an approach to such an inquiry could lead a panel into error. To appreciate properly 
whether a measure is even-handed, an inquiry into  the nexus between the regulatory distinctions 
found in the measure and the measure's policy objective may have to encompass also, or to be supplemented by, consideration of whether the differences in the treatment accorded to different 
groups of products by virtue of those distin ctions, and the resulting detrimental impact, are 
disproportionate in the light of the objective pursued.
582  
7.154.  We also explained above that an assessment of the "calibration" of a measure and the 
regulatory distinctions that it draws is not, in and of itself, a generally applicable test of whether 
detrimental impact stems exclusively from a legitimate regulatory distinction. Rather, this term is nomenclature from the original proceedings that was used by the United States, and employed by 
the Appellate Body, to test whether the origin al tuna measure was even-handed. Indeed, the 
                                               
578 Mexico's appellee's submission, para. 123. 
579 Mexico's appellee's submission, para. 129. Mexico argues that the amended tuna measure's objective 
in no way allows some level of "acceptable" mortality or serious injury in the dolphin-safe information. (Ibid.) 
580 Mexico's appellee's submission, paras. 173-174. 
581 Mexico's appellee's submission, para. 173 (quoting United States' appellant's submission, para. 344 
(emphasis original)). 
582 Appellate Body Reports, US – COOL , para. 347. WT/DS381/AB/RW 
 
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 Appellate Body found in the original proceedings that "the United States ha[d] not demonstrated 
that the difference in labelling conditions for tuna  products containing tuna caught by setting on 
dolphins in the ETP, on the one hand, and for tuna products containing tuna caught by other fishing methods outside the ETP, on the other hand, [was] 'calibrated' to the risks to dolphins 
arising from different fishing method s in different areas of the ocean."
583 It followed from this that 
"the United States ha[d] not demonstrated that the detrimental impact of the US measure on Mexican tuna products stem[med] exclusively from a legitimate regulatory distinction."
584 The 
Appellate Body added that, "[i]n these circumstances, [it was] not persuaded that the 
United States ha[d] demonstrated that the measure [was] even-handed  in the relevant 
respects."585  
7.155.  These passages, in our view, demonstrate that the Appellate Body's assessment of 
"even-handedness" in the original proceedings was focused on the question of whether the original 
tuna measure was "calibrated" to the risks to dolphins arising from different fishing methods in different areas of the oceans. They further show  that this question was answered through a 
comparison of the conditions of access to the dolphin-safe label for tuna products derived from 
tuna caught within the ETP large purse-seine fishery, on the one hand, with those applied to tuna products derived from tuna caught outside that fishery by fishing methods other than setting on 
dolphins, on the other hand. By engaging with the United States' arguments as it did, the 
Appellate Body accepted the premise that such regime  will not violate Article 2.1 if it is properly 
"calibrated" to the risks to dolphins arising from different fishing methods in different areas of the oceans.
586 This, in turn, indicates that, in the co ntext of the original proceedings, the 
Appellate Body considered appropriate an analysis involving: first, an identification of whether 
different tuna fishing methods in different areas of the oceans pose different risks to dolphins; and, second, examination of whether, in the light of these risks, the different treatment created by 
the relevant regulatory distinction shows that, as between different groups, the treatment 
accorded to each group is commensurate with the relevant risks, taking account of the objectives of the measure. This assessment was conducted in order to determine whether or not the original 
US dolphin-safe labelling regime was even-handed.  
7.156.  We also consider it appropriate for WTO Members to seek guidance in the reasoning set 
out in adopted Appellate Body and panel report s when seeking to bring their inconsistent 
measures into compliance with their obligations under the covered agreements. Indeed, this 
contributes to the security and predictability of the multilateral trading system, as well as to the 
prompt settlement of disputes. In these compliance proceedings, the United States has defended its dolphin-safe labelling regime from the claim raised by Mexico under Article 2.1 of the 
TBT Agreement by explaining why the distinctio ns drawn under the amended tuna measure stem 
exclusively from a legitimate regulatory distinction in terms very similar to those that it used in the original proceedings. The United States has argued  that, to the extent that there is detrimental 
impact on Mexican tuna products, by virtue of the differences in the labelling conditions for tuna 
products containing tuna caught inside and outside the ETP large purse-seine fishery, such differences are explained by, or "calibrated" to, the different risks to dolphins arising from different fishing methods in different areas of the oceans.
587 Before the Panel, the United States also 
submitted extensive arguments and evidence seekin g to show that the different risks associated 
with different fisheries explain the differentia l treatment accorded under the amended tuna 
measure. 
7.157.   These considerations suggest to us that the Panel's inquiry in these Article 21.5 
proceedings should have included an assessment of whether, under the amended tuna measure, 
the differences in labelling conditions for tuna products containing tuna caught in the ETP large 
purse-seine fishery, on the one hand, and for tuna products containing tuna caught in other 
                                               
583 Appellate Body Report, US – Tuna II (Mexico) , para. 297. 
584 Appellate Body Report, US – Tuna II (Mexico) , para. 297. 
585 Appellate Body Report, US – Tuna II (Mexico) , para. 297. (emphasis added) 
586 We also agree with the United States that acceptance of such an approach is implicit in the 
Appellate Body's statement that requir ing certification by an observer, ra ther than by a captain, "may be 
appropriate in circumstances in which dolphins face higher  risks of mortality or seri ous injury". (United States' 
appellant's submission, para. 201 (quoting Appellate Body Report, US – Tuna II (Mexico) , fn 612 to para. 296)) 
587 United States' appellant's submission, paras. 195-196. WT/DS381/AB/RW 
 
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 fisheries, on the other hand, are "calibrated" to the likelihood that dolphins would be adversely 
affected in the course of tuna fishin g operations in the different fisheries.588 
7.158.  Having reached this preliminary conclusion, we next examine more specifically the inquiry 
that the Panel did undertake, including the questi on of whether such analysis encompassed an 
evaluation and comparison of the different risks to dolphins associated with different fishing 
methods in different oceans. As we have indicated, the Panel explained that, "in examining whether detrimental treatment stems exclusively from  a legitimate regulatory distinction, a panel 
may take into account the extent to which the identified detrimental treatment is explained by, or 
at least reconcilable with, the objectives [pursued] by the measure at issue."
589 The Panel found 
that the different certification requirements are not even-handed because "captains may not necessarily and always have the technical skills requir ed to certify that no dolphins were killed or 
seriously injured in a set or other gear deployment, and this may result in inaccurate information 
being passed to consumers, in contradiction with the objectives of the amended tuna measure."
590 
In analysing the different tracking and verification requirements, the Panel found that there is no 
rational or obvious connection between the amended tuna measure's imposition of a lighter burden 
on tuna caught outside the ETP large purse-seine fishery and the objectives of the amended tuna 
measure, and that none of the explanations prov ided by the United States suggested otherwise.591 
On these bases, the Panel found that the certification and tracking and verification requirements in 
place under the amended tuna measure are no t even-handed, and therefore do not stem 
exclusively from a legitima te regulatory distinction.592 
7.159.  In our view, the manner in which the Pane l applied the legal standard to ascertain the 
even-handedness of the certification and tracking and verification requirements presents certain 
difficulties. The first and most important of thes e arises from the segmented analysis adopted by 
the Panel. As we have indicated, the certification and tracking and verification requirements work 
together with the substantive conditions of the amended tuna measure to limit access to the 
dolphin-safe label. This means, in our view, that it is only when the conditions of access are viewed together that the nexus between the regulatory distinctions found in the measure and the 
measure's policy objectives can be understood. Assessing these discrete sets of requirements in 
isolation from the other elements of the measure may thus hinder a comprehensive analysis of the 
design and structure of the measure and how it pursues its objectives. Moreover, the Panel's segmented analysis of the amended tuna measure al so appears to have led the Panel to overlook 
that, at least when compared to the original tuna measure, the amended tuna measure as a whole  
furthers the objectives of providing information to consumers and protecting dolphins from harms arising from tuna fishing. For these reasons, we consider that the Panel's decision to adopt a 
segmented analytical approach prevented it from properly applying the legal standard that it 
articulated. 
7.160.  We next consider whether, notwithstanding that it did not explicitly engage with the 
explanations provided by the United States for the differences in the respective sets of certification 
and tracking and verification requirements, the Pa nel's analyses of the even-handedness of these 
requirements in fact reflect that it did assess and take due account of the different risks associated with tuna fishing in different fisheries. If, for ex ample, the Panel established that the risks posed to 
dolphins in the different fishing areas and by the different fishing methods are the same, then it 
may properly have reached the conclusion that trea ting them differently is not "even-handed". If, 
however, the Panel considered that the risk profiles are different, then further inquiry would have 
been needed into whether the regulatory distin ctions drawn by the amended tuna measure, and 
the resulting detrimental impact, could be expl ained as commensurate with the different risks 
associated with tuna fishing in different oceans and using different fishing methods. 
7.161.  In its analysis of the eligibility criteria, the Panel found that there is a difference in the 
nature of the risks posed to dolphins by the fish ing method of setting on dolphins, as opposed to 
other fishing methods. In particular, the Panel stated that it agreed with the United States that "even if  there are tuna fisheries using … gear types that produce the same number of dolphin 
mortalities and serious injuries allowed or caused in the ETP … it is simply not the case that such 
                                               
588 Appellate Body Report, US – Tuna II (Mexico) , para. 286. 
589 Panel Report, para. 7.196. 
590 Panel Report, para. 7.233.  
591 Panel Report, paras. 7.392 and 7.400. 
592 Panel Report, paras. 7.233 and 7.401. WT/DS381/AB/RW 
 
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 fisheries are producing the same level of unobserved harms".593 In reaching this finding, the Panel 
appears to have focused solely on its understanding that the unobserved  harms differed as 
between setting on dolphins and other fishing methods. On this basis, the Panel found that the new evidence did not overcome or contradict the finding from the original proceedings that setting 
on dolphins causes a level of unobserved harms to dolphins that is not found with other fishing 
methods. By focusing solely on its understanding that the unobserved  harms differed between 
setting on dolphins and other fishing methods, the Panel did not consider the relative risks posed 
by the relevant fishing methods in respect of observed  mortality or serious injury, and therefore 
did not resolve the questions of the overall levels of risk in the different fisheries and how they 
compare to each other. However, it was precisely this kind of examination that was the focus of the Appellate Body's analysis in the original proceedings, which revolved around an assessment of 
the US dolphin-safe labelling provisions in the light of the overall levels of risk in the relevant 
fisheries, including risks of both observed and unobserved harms. Indeed, we recall that, in its conclusion, the Appellate Body emphasized that "the US measure fully addresse[d] the adverse 
effects on dolphins resulting from setting on dolphins in the ETP, whereas it d[id] 'not address 
mortality (observed or unobserved) arising from fishing methods other than setting on dolphins outside the ETP'."
594 Therefore, we do not consider that, in  examining the eligibility criteria, the 
Panel's analysis reflects that it did assess and take due account of the different risks associated 
with tuna fishing in different oceans and using different fishing methods in a way that would have enabled it properly to evaluate the parties' arguments regarding the even-handedness of the amended tuna measure's regulatory distinctions. 
7.162.  In assessing the certification and tracking and verification requirements, the Panel stated 
that it considered these two regulatory distinctions to be relevant "only to tuna eligible and intended to receive the dolphin-safe label".
595 Accordingly, in the Panel's view, "tuna that is either 
ineligible to access this label (i.e. tuna caught by setting on dolphins) or not intended to be sold 
under the dolphin-safe label is not affected by these regulatory distinctions."596 We understand 
from this that, as it did in analysing the detrimental impact of each of the three distinctions, the 
Panel's analyses of the even-handedness of th e certification and tracking and verification 
requirements involved, in each case, a comparison of the treatment accorded to tuna products derived from tuna caught in the ETP large purse-seine fishery other than on a trip involving setting on dolphins, on the one hand, with that accorded to tuna products containing tuna caught outside 
the ETP large purse-seine fishery other than on a trip involving setting on dolphins, on the other 
hand. As explained below, however, it is not entirely clear whether the Panel considered, for 
purposes of these analyses, that the respective risks to dolphins posed in these fisheries compared 
was the same, different, or simply not relevant to its analyses. Nor did the Panel explicitly indicate 
whether it considered the respective risks to dolphins identified by the original panel, and "reaffirm[ed]"
597 by this Panel, in its analysis of the eligibility criteria, to also be relevant in 
analysing the even-handedness of the certificatio n and tracking and verification requirements.  
7.163.  In examining the different certification requirements, the Panel devoted most of its 
reasoning to a comparison of the different tasks carried out by observers in the ETP and captains, 
as well as their respective expertise, training, and education for purposes of providing 
certifications. In particular, the Panel based its finding that "the different certification requirements 
are not even-handed" on the conclusion that "captains may not necessarily and always have the technical skills required to certify that no dolphi ns were killed or seriously injured" and that 
"this may result in inaccurate information being passed to consumers, in contradiction with the 
objectives of the amended tuna measure."
598 The Panel's reasoning includes only limited 
references to the risks to dolphins in the relevant fisheries, and does not address whether, in the 
light of the risk profiles, the different treatment created by the relevant regulatory distinctions 
show that, as between different groups, the treatm ent accorded to each group is explained by, and 
appropriately tailored to, the relevant risks. Havi ng identified the "key problem with the amended 
tuna measure" as being that "the United States has not explained why its measure assumes that 
captains have at their disposal the skills necessary to ensure accurate certification", the Panel 
                                               
593 Panel Report, para. 7.135 (quoting United States' first written submission to the Panel, para. 113 
(emphasis original)). 
594 Appellate Body Report, US – Tuna II (Mexico) , para. 297 (quoting Original Panel Report, 
para. 7.544). (emphasis original) 
595 Panel Report, para. 7.143. 
596 Panel Report, para. 7.143. 
597 Panel Report, para. 7.126. 
598 Panel Report, para. 7.233. WT/DS381/AB/RW 
 
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 indicated that, "[a]ccordingly", it was "not convinced that the different certification requirements, 
as currently designed, sufficiently address 'the risks to dolphins arising from different fishing methods in different areas of the ocean'".
599 While this statement could be read to suggest that the 
Panel acknowledged that an examination of the different risk profiles attached to the different 
fishing methods in different areas of the oceans might have been relevant to its analysis, it does 
not appear to us that such an examination formed part of the Panel's analysis or served as a basis for its conclusions.
600 
7.164.  As noted above, the Panel also analys ed the even-handedness of the certification 
requirements assuming arguendo  that the United States, rather than Mexico, bore the burden of 
proof. In this alternative analysis, the Panel examined certain facts related to the risks to dolphins arising from various fishing methods in different areas of the oceans. The Panel accepted the 
United States' argument regarding the "special and, in some senses, 'unique' nature of the harms 
that the ETP large purse seine fishery poses to dolphins".
601 The Panel considered that Mexico's 
arguments and evidence relating to tuna-dolphin association and the prevalence of setting on 
dolphins outside the ETP were not sufficient to rebut the United States' argument that the situation 
in the ETP is unique or different in a way that wo uld justify the different treatment of the ETP large 
purse-seine fishery and other fisheries.602 On this basis, the Panel observed that it "would find that 
the United States ha[d] made a prima facie  case that the different certification requirements stem 
exclusively from a legitimate regulatory distinction".603 To us, this part of the Panel's reasoning 
appears to have employed a concept that looks li ke "calibration". Ultimately, however, the Panel 
concluded that the different certification requirements are not even-handed. Pointing out that the 
United States had not rebutted evidence submi tted by Mexico concerning the complexity of 
certifying the dolphin-safe status of a tuna catch, the Panel stated that it "would find that the United States ha[d] not explained sufficiently why it assumes that captains are capable of carrying 
out an activity that the amended tuna measure itself recognizes as highly complex and for which 
training and education are required".
604 For the Panel, the lack of explanation concerning the 
technical capacities of captains meant that the different certification requirements could not be 
said to be even-handed, and as such to stem exclusively  from a legitimate regulatory 
distinction.605  
7.165.  It appears to us that certain aspects of this part of the Panel's analysis suggest that the 
Panel gave some consideration to the respective risk profiles associated with different fishing 
methods in different areas of the oceans. Thus, for example, the Panel explained that the 
distinction between different fishing methods is "especially important" given that setting on is "inherently dangerous" to dolphins, even where no dolphin is seen to be killed or seriously injured, 
"because it has unobservable deleterious effects on dolphins' physical and emotional 
well-being".
606 At the same time, we note that, notwithstanding that it had stated that the 
treatment of tuna products derived from tuna caught by setting on dolphins would not be relevant 
to its analyses of the certification and tracking and verification requirements, the Panel's 
discussion of the respective risk profiles seems to have focused exclusively on this fishing technique. We are not certain whether, in the co ntext of the different certification requirements, 
                                               
599 Panel Report, para. 7.234 (quoting Appellate Body Report, US – Tuna II (Mexico) , para. 297). 
600 While an assessment of the di fferent risks to dolphins does not appear to have guided the Panel's 
analysis in the context of its analysis of Mexico's cl aim concerning the certification requirements, found in 
paragraphs 7.195-7.234 of its Report, the Panel did discuss in its analysis of the eligibility criteria, new evidence submitted in the compliance proceedings regard ing the respective "harms" to dolphins within the ETP 
large purse-seine fishery as compared to other fisher ies. (See Panel Report, paras. 7.129-7.135) We note, 
however, that in its analysis of the eligibility criteria the Panel appeared to be examining different groups of tuna products than in its analysis of the certification requirements. 
601 Panel Report, para. 7.238. 
602 Panel Report, para. 7.241. The Panel highlighted that Mexico's evidence suggested that, "even 
though there may be some interaction between tuna an d marine mammals, includin g dolphins, outside of the 
ETP, 'dolphins in the Atlantic, Indian, and western Pacifi c Oceans [do not associate with tuna] as systematically 
as they do in the Eastern Tropical Pacific'." (I bid. (quoting National Marine Fisheries Service, An Annotated 
Bibliography of Available Literature Regarding Cetacean Interactions with Tuna Purse-Seine Fisheries Outside of the Eastern Tropical Pacific Ocean , Administrative Report LJ-96-20 (November 1996) (Panel Exhibit MEX-40), 
p. 2)) The Panel added that, "although dolphins may occasionally and incidentally be set on outside the ETP, it is only inside the ETP that setting on dolphins is practiced consistently or 'systematically'." (Ibid., para. 7.242) 
603 Panel Report, para. 7.245. 
604 Panel Report, para. 7.246. 
605 Panel Report, para. 7.246. (emphasis original) 
606 Panel Report, para. 7.244. WT/DS381/AB/RW 
 
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 the Panel ultimately considered that the risk profiles of the relevant fisheries giving rise to the 
different groups of tuna products are the same  or different . Moreover the Panel's ultimate 
conclusion that the different certification requirements were not even-handed under Article 2.1 was due to the fact that the United States had failed to "explain [] sufficiently why it assumes that 
captains are capable of carrying out an activity that the amended tuna measure itself recognizes 
as highly complex and for which training and education are required".
607 Therefore, while the 
concept of different risks to dolphins in the relevant fisheries seems to have played some part in 
its analysis, we do not see that such analysis encompassed a clear identification of the respective 
risks or an assessment of whether such risks we re addressed in an even-handed manner by the 
different certification requirements.608  
7.166.  In analysing the even-handedness of the tr acking and verification requirements, the Panel 
dismissed the United States' argument that the diffe rent tracking and verification requirements are 
justified or explained in the light of the higher  degree of risk to dolphins in the ETP large 
purse-seine fishery. The Panel explained that any higher risk "does not explain why the tracking 
and verification requirements, which by their very nature concern the movement of fish 
subsequent to the time of catch , differ between fisheries to the detriment of like Mexican tuna and 
tuna products".609 According to the Panel, the "different risk profiles" of different fisheries may 
explain regulatory distinctions concerning the eligibility criteria for fishing methods, as well as the 
need for an independent observer to monitor and certify during and immediately following the fishing activity itself, but do not explain the tr acking and verification requirements, which are 
triggered after the tuna has been caught.
610 We are not convinced that, as the Panel seems to 
have thought, considerations of the similarities an d differences in risks may not be reflected in and 
relevant to all stages of the capture and subseque nt transport and processing of tuna. We read the 
Panel as having taken the view that the relevant risk profiles would change  or become irrelevant  to 
the analysis of "even-handedness" merely because those requirements regulate a situation that 
occurs after the tuna has been caught. In our view , this approach by the Panel does not seem to 
comport with its own reasoning that the accuracy of the US dolphin-safe label can be compromised 
at any stage of the tuna production stage, in contradiction with the ob jectives of the amended 
tuna measure.611 Moreover, we consider that the Panel's approach also runs counter to our 
observations that an assessment of the even-han dedness of the amended tuna measure must take 
account of the fact that its various elements – the eligibility criteria, the certification requirements, 
and the tracking and verification requirements – es tablish a series of conditions of access to the 
dolphin-safe label that are cumulative and highly interrelated. 
7.167.  In the light of these considerations, it is clear that, since the Panel did not consider the 
risks to dolphins to be relevant to its analys is of the even-handedness of the tracking and 
verification requirements, the Panel did not seek to identify those risks in respect of eligible tuna 
caught both inside and outside the ETP large purse-seine fishery in this part of its analysis. Nor did 
the Panel compare the different tracking and verification requirements in the light of those risks 
and the amended tuna measure's objectives concerning the protection of dolphins and providing accurate consumer information. 
                                               
607 Panel Report, para. 7.246. 
608 By contrast, the analysis by the panelist who wrote a separate opinion of the even-handedness of the 
different certification requir ements expressly discusses the notion of "risk profile" and how that applies to the 
different fisheries in the present dispute, using the te rm "calibration". (Panel Report, paras. 7.276 and 7.282) 
However, we do not necessarily see that, in assessin g the even-handedness of the different certification 
requirements, this panelist made a comp lete assessment of the di fferent levels of risk in different fisheries. 
Instead, the conclusions reached were on the basis of a general observation that, "given the higher degree of risk in the ETP large purse seine fish ery ["particularly harmful" versus "a s a general matter, significantly less 
serious" in fisheries other than th e ETP large purse-seine fishery], it is … entirely even-handed for the 
United States to tolerate a smaller margin of error in th at latter fishery, and accord ingly to require observers in 
that fishery but not in others." (Ibid., para. 7.258) 
609 Panel Report, para. 7.398. (emphasis original) 
610 Panel Report, para. 7.398. 
611 We recall that, in the context of the certification requirements, the Panel found that the United States 
had not rebutted Mexico's showing that captains may no t necessarily and always have the technical skills 
required to certify that no dolphins were killed or se riously injured, and that this may result in inaccurate 
information being passed to consumer s, in contradiction with the objectives of the amended tuna measure. 
(Panel Report, para. 7.233) Similarly, in the context of  the tracking and verification requirements, the Panel 
indicated that the different tracking and verification requirements have a detrimental impact on Mexican tuna 
and tuna products, including because they may make it  more likely that tuna caught other than by large 
purse-seine vessels will be incorrectly labelled as dolphin safe. (Ibid., para. 7.391) WT/DS381/AB/RW 
 
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 7.168.  As an additional argument, the United States contends that any detrimental impact caused 
by the certification and tracking and verification requirements stems exclusively from a legitimate regulatory distinction because the differences lead ing to the detrimental impact can be explained 
by a legitimate, non-discriminatory reason, namely, that these differences reflect that the parties 
to the AIDCP have consented to impose a unique observer programme on their tuna industries, 
while other regulatory authorities have not imposed like requirements.
612 In principle, we do not 
exclude that the fact that the amended tuna measure sets out rules for the ETP large purse-seine 
fishery reflecting requirements imposed under the AIDCP may be relevant to the question of 
whether the detrimental impact stems exclusively from a legitimate regulatory distinction under Article 2.1 of the TBT Agreement, in particular because it may shed light on the reasons for the 
distinctions drawn as well as on the nexus betw een such distinctions and the objectives of the 
relevant measure. Yet, tying some  aspects of a measure to an international agreement cannot, 
alone, suffice to establish that the measure does not embody discrimination of a type prohibited under Article 2.1. Moreover, we observe that, wh ile there is an absence of any international 
regulation comparable to the AIDCP with respect to all tuna fisheries other than the ETP large 
purse-seine fishery, the amended tuna measure sets forth  conditions  for those tuna fisheries. In 
this dispute, the relevant regulatory distinction drawn by the amended tuna measure consists of 
the requirements applicable to tuna products derived from tuna caught in the ETP large 
purse-seine fishery vis-à-vis the requirements applicable to tuna products derived from tuna caught in other fisheries. As we have said ab ove, assessing the even-handedness of the amended 
tuna measure requires looking at both sides of the regulatory distinctions that it draws. The 
AIDCP, however, is mainly relevant for one side of this regulatory distinction: the requirements 
applicable to tuna caught in the ETP large purse-seine fishery. Moreover, we observe that the relevant certification and tracking and verification requirements that the amended tuna measure 
applies in respect of tuna caught in the ETP large purse-seine fishery are not identical to, or 
coextensive with, those under the AIDCP, particularly given that the amended tuna measure, unlike the AIDCP, disqualifies from access to the dolphin-safe label all tuna products derived from 
tuna caught by setting on dolphins. 
7.169.  In sum, in the light of the circumstances of  this dispute and the nature of the distinctions 
drawn under the amended tuna measure, we are of the view that, in applying the second step of 
the "treatment no less favourable" requirement under Article 2.1 of the TBT Agreement, the Panel 
was required to assess whether the certification and tracking and verification requirements are 
"calibrated" to the risks to dolphins arising from different fishing methods in different areas of the oceans. Our review of the Panel Report reveals that the Panel's analysis failed to encompass 
consideration of the relative risks to dolphins from different fishing techniques in different areas of 
the oceans, and of whether the distinctions that the amended tuna measure draws in terms of the 
different conditions of access to the dolphin-safe label are explained in the light of the relative 
profiles. We therefore consider that the Panel failed to take full account of "the particular 
circumstances" of this case, including "the design, architecture, revealing structure, operation, and application" of the amended tuna measure, as well as of the manner in which similar circumstances pertaining to the original tuna measure had been assessed in the original 
proceedings. In addition, due to the segmented ap proach that it adopted in its analyses of the 
different sets of certification and tracking and verification requirements, the Panel did not properly apply the legal test that it had identified as relevant to an assessment of even-handedness, 
namely, "whether the detrimental treatment can be reconciled with, or is rationally related to, the 
policy pursued by the measure at issue."
613 The Panel thus erred in its discrete assessments of the 
even-handedness of the different certification re quirements, and of the different tracking and 
verification requirements. Accordingly, we find that, in assessing Mexico's claim that the 
certification requirements and the tracking and verification requirements are not "even-handed", 
the Panel erred in its application of the second step of the "treatment no less favourable" test under Article 2.1 of the TBT Agreement. 
7.2.3.2.3.3  Whether the Panel erred in find ing that, by virtue of the determination 
provisions, the detrimental impact does not stem exclusively from a legitimate 
regulatory distinction 
7.170.  The United States raises two challenges to the Panel's findings regarding the 
"determination provisions". First, the United States argues that, in finding that the "gap" in the 
                                               
612 United States' appellant's submission, paras. 209 and 347. 
613 Panel Report, para. 7.91. WT/DS381/AB/RW 
 
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 determination provisions does not stem exclusively from a legitimate regulatory distinction, the 
Panel erred by improperly making the case for Mexico. Second, the United States contends that the Panel erred in making its findings on the determination provisions based solely on their design, and not on their application.
614  
7.171.  Before addressing the United States' claims, we begin by recalling the Panel's explanation 
of the determination provisions, as well as the main findings by the Panel regarding these provisions. After reaching its conclusions regarding captains' certifications, the Panel turned to 
examine an additional aspect of the amended tuna measure that it considered to bear on, and to 
be of "some importance to"
615, its analysis of the even-handedn ess of the different certification 
requirements. The Panel noted that the United States had confirmed in response to a question from the Panel that the determination of regular and significant mortality or serious injury 
provided for under Section 216.91(a)(4)(iii) of the implementing regulations does not apply to 
purse-seine fisheries outside the ETP, and that the determination of regular and significant association that may be made pursuant to Section 216.91(a)(2)(i) of those regulations only 
applies to the non-ETP purse-seine fishery.
616 In this regard, the Panel made the following finding: 
[T]he determination provisions appear to reduce the range of circumstances in which 
observers can be required outside of the ETP large purse seine fishery (or in small 
purse seine fisheries inside the ETP), further entrenching the less favourable 
treatment caused by the different certification requirements. This is so because the design of the determination provisions is such that like tuna products may be subject to different requirements even where, as a matter of fact, the conditions in a 
non-ETP fishery (or a small purse seine fishery inside the ETP) are the same as those 
in the ETP large purse seine fishery. They thus seem to us to represent a further way in which the amended tuna measure lack s even-handedness in its treatment of 
different tuna fishing methods in different oceans, and may also make it easier for 
tuna caught other than by [a] large purse seine vessel in the ETP to be incorrectly labelled as dolphin-safe, thus modifying the conditions of competition in the US tuna 
market to the detriment of Mexican tuna and tuna products.
617 
7.172.  In addition, the Panel held that "the determination provisions appear to be arbitrary in the 
sense that they are difficult to reconcile with, or justify by reference to, the objectives pursued by 
the amended tuna measure itself."618 The Panel noted that the United States had not explained 
why purse-seine vessels outside the ETP cannot be subject to a declaration that they are causing 
regular and significant dolphin mortality.619 Moreover, the Panel expressed doubt about the 
United States' argument that the existence and nature of tuna-dolphin association has no impact 
on the degree of mortality or serious injury caused by fishing methods other than setting on 
dolphins, and observed that this seemed incompat ible with the United States' own explanation of 
the reasons why observers are necessary in the ETP large purse-seine fishery.620 
7.173.  For these reasons, the Panel expressed its understanding that the determination provisions 
open up a "gap" in the certification procedures applied outside the ETP large purse-seine fishery.621 
The Panel emphasized that "a determination of regular and significant mortality cannot be made in respect of purse seine fisheries outside the ETP, and a determination of regular and significant 
tuna-dolphin association cannot be made in respect of non-purse seine fisheries."
622 This means 
that, in some cases, fisheries other than the ETP large purse-seine fishery may be treated differently, and less stringently, under the amende d tuna measure even where the conditions in 
that fishery mirror those in the ETP large purse-seine fishery, either in terms of the level of dolphin 
mortality or the degree of tuna-dolphin associat ion. The Panel therefore expressed the view that, 
by virtue of the determination provisions, the different certification procedures lack 
                                               
614 The United States' additional contention that the Panel acted inconsistently with Article 11 of the DSU 
by failing to base its findings regarding the determination provisions on a sufficient evidentiary basis is addressed in the next subsection. 
615 Panel Report, para. 7.247. 
616 Panel Report, para. 7.249 (referring to United Stat es' response to Panel question No. 59, para. 295). 
617 Panel Report, para. 7.258. (fn omitted) 
618 Panel Report, para. 7.259. 
619 Panel Report, para. 7.260. 
620 Panel Report, para. 7.261. 
621 Panel Report, para. 7.263. 
622 Panel Report, para. 7.263. (fns omitted) WT/DS381/AB/RW 
 
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 even-handedness.623 Moreover, although one panelist had disagreed with the Panel majority 
regarding the even-handedness of the different ce rtification requirements under the amended tuna 
measure, that panelist agreed with the majority th at "the fact that a determination of regular and 
significant mortality cannot be made in respect of purse seine fisheries outside the ETP, and the 
fact that a determination of regular and signific ant tuna-dolphin association cannot be made in 
respect of non-purse seine fisheries, has not been explained or justified", and that, therefore, this 
aspect of the different certification requirements is inconsistent with Article 2.1 of the 
TBT Agreement.624 
Whether the Panel improperly made the case  for Mexico in reaching its findings 
regarding the determination provisions 
7.174.  The United States submits that the Panel erred in finding that the determination provisions 
"represent a further way" in which the certification requirements "lack[] even-handedness".625 In 
the United States' view, "Mexico put forward no affirmative argument  with regard to the 
determination provisions in its case-in-chief for its Article 2.1 claim" and, as a consequence, the 
United States did not present any rebuttal arguments in that respect.626 The Panel, however, 
raised the issue on its own initiative in its written questions to the United States, and reached its conclusions despite the fact that Mexico did not "explicitly connect" the determination provisions to 
its claims under Article 2.1 until it submitted its comments on the United States' responses to 
Panel questions.
627 Accordingly, the United States claims that the Panel improperly made a 
prima facie  case for the complainant and relieved Mexico of its duty to prove its claims under 
Article 2.1.628 
7.175.  Mexico rejects the United States' claim and observes that it identified the determination 
provisions in its first written submission, where it explained that the US Department of Commerce (USDOC) has never made any determination under those provisions
629, and in its responses to 
Panel questions, where it argued that the failur e of the USDOC to make any such determination 
was "an indication of arbitrariness".630 Mexico acknowledges that it did not argue that "the 
determination provisions themselves directly result in detrimental impact".631 However, in Mexico's 
opinion, it need not have done so, because the relevant detrimental impact of the US dolphin-safe 
labelling regime was definitively established by the panel and the Appellate Body in the original 
proceedings. Further, in examining whether the determination provisions are even-handed, it was appropriate for the Panel to focus on their "design, architecture and revealing structure" because 
such provisions "have never been applied".
632 
7.176.  In addressing this issue, we first recall that, while panels enjoy latitude to develop their 
re as oning  and  to d e c id e  whic h  e vid e n c e  on the  re c ord  the y wi s h to re ly  u p on in re ac h ing  the ir 
findings633, such discretion is not unfettered. Instead, it is limited by the requirement that the 
complainant satisfy its burden of proof by adduci ng evidence and arguments sufficient to make a 
prima facie case in relation to each of the elements of its claims.634 This does not mean that a 
complainant must necessarily put forward all evidence and arguments relevant to the question of 
the measure's consistency with the covered agreements. However, at a minimum, it must adduce arguments and evidence that, in the absence of effective refutation by the respondent, would 
enable a panel to rule in its favour.
635 A panel may not use its interrogative powers to make the 
                                               
623 Panel Report, para. 7.258.  
624 Panel Report, paras. 7.282-7.283. 
625 United States' appellant's submission, para. 213 (quoting Panel Report, para. 7.281). 
626 United States' appellant's submission, para. 218. (emphasis original) 
627 United States' appellant's submission, para. 219. 
628 United States' appellant's submission, paras. 225-226. 
629 Mexico's appellee's submission, para. 137 (referring to Mexico's first written submission to the Panel, 
paras. 21, 41, and 290). 
630 Mexico's appellee's submission, para. 137 (refe rring to Mexico's respon ses to Panel questions 
Nos. 21 and 22). 
631 Mexico's appellee's submission, para. 139. 
632 Mexico's appellee's submission, para. 139. 
633 See Appellate Body Reports, Canada – Aircraft , para. 192; EC – Hormones , para. 156; Chile – Price 
Band System , para. 166; US – Gambling , para. 280;  Mexico – Anti-Dumping Measures on Rice , para. 156; and 
Canada – Renewable Energy / Canada – Feed-In Tariff Program , para. 5.215. 
634 See Appellate Body Reports, US – Gambling , para. 140; and US – Wool Shirts and Blouses , p. 16, 
DSR 1997:I, p. 336. 
635 See Appellate Body Reports, Japan – Apples , para. 159; and EC – Hormones , para. 98. WT/DS381/AB/RW 
 
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 case for the complainant636, nor to make good the absence of argumentation on a party's 
behalf.637 
7.177.  Where, however, the complainant has made out a prima facie case, a panel may in 
principle draw from arguments and evidence on  the record, or develop its own reasoning in 
reaching its findings638, provided that it does so consistently with the requirements of due process. 
While arguments may be progressively refined throughout the course of the proceedings639, each 
party must be afforded a meaningful opportunity to comment on the arguments and evidence 
adduced by the other party.640 Finally, a panel is not required to test its intended reasoning with 
the parties.641 However, due process could be compromised in circumstances where the panel 
adopts an approach that departs so radically from the cases put forward by the parties that the parties are left guessing as to what pr oof they would have needed to adduce.
642 
7.178.  With these considerations in mind, we briefly describe the progression of the parties' 
arguments and the Panel's inquiry concerning the determination provisions throughout the proceedings. In its first written submission, Mexi co referred to the determination provisions by 
noting, inter alia , that the USDOC has never defined the term "regular and significant", nor made 
any determination of either regular tuna-dolphin association or of mortality or serious injury of dolphins with respect to fisheries outside the ETP large purse-seine fishery.
643 Mexico relied on the 
absence of any such determinations to support its view that the certification requirements lack 
even-handedness.644 After the first substantive meeting, the Panel sent the parties a set of written 
questions in order to explore further the applic ation of the determination provisions by the 
Administrator. In response to questioning from the Panel, both parties confirmed that the 
Administrator has not made any determination of regular and significant mortality or serious injury 
or a determination of regular and significant tuna-dolphin association.645  
7.179.  The Panel also asked the United States a number of questions concerning the functioning 
of the determination provisions. In particular, the Panel asked the United States to confirm its 
understanding that, if the NMFS Assistant Admi nistrator makes a determination of regular and 
significant tuna-dolphin association with respect to a given fishery, the observer coverage so 
imposed would concern only purse-seine vessels (as opposed to all vessels) operating in that 
fishery. The United States confirmed the Panel's understanding.646 After receiving written 
responses from the parties to its initial round of written questions, the Panel additionally asked the parties to confirm whether it was correct in understanding that: 
… large and small purse seine fisheries outside the ETP can never be required to have 
observers on board because of "regular and si gnificant mortality or serious injuries of 
dolphins". Rather, observers can only be re quired in such fisheries where there is 
"regular and significant association between dolphins and tuna similar to the ETP". 
Conversely, … non-purse seine fisheries outside the ETP, as well as small purse seine fisheries inside the ETP, can only be required to have observers in board in cases 
where they are causing "regular and significant mortality or serious injury of 
dolphins". A determination of "regular and significant association" cannot be made in respect of these fisheries.
647 
                                               
636 See Appellate Body Reports, US – Continued Zeroing , para. 343; and Japan – Agricultural 
Products II , para. 129. 
637 See Appellate Body Report, EC – Fasteners (China) , para. 566. 
638 See Appellate Body Report, US – Gambling , para. 282. 
639 See Appellate Body Reports, EC – Bananas III , para. 141; Korea – Various Measures on Beef , 
para. 88; Chile – Price Band System , para. 181; and Dominican Republic – Import  and Sale of Cigarettes , 
para. 121. 
640 See Appellate Body Reports, Thailand – Cigarettes (Philippines) , para. 150; Australia – Salmon , 
para. 278; and US – Gambling , para. 270. 
641 Appellate Body Report, US – Large Civil Aircraft (2nd complaint) , para. 1137. 
642 See Appellate Body Reports, US – Large Civil Aircraft (2nd complaint) , fn 2323 to para. 1137; and 
US – Continued Zeroing , para. 347. 
643 Mexico's first written submission to the Panel, paras. 289-290. 
644 Mexico's first written submission to the Panel, paras. 295 and 304. 
645 Mexico's responses to Panel questions No. 21, para. 93 and No. 22, para. 95; United States' 
responses to Panel questions No. 21, paras. 133-134 and No. 22, para. 145. 
646 United States' response to Panel question No. 55, para. 280. 
647 Panel Question No. 60 to both parties. WT/DS381/AB/RW 
 
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 7.180.  In responding to this question, Mexico submitted that the determination provisions are 
designed in a way whereby: (i) "even if purse seine vessels operating in a region outside the ETP are causing substantial dolphin mortalities, that region could never be the subject of a determination that there is regular and significant mortality or serious injury of dolphins on that 
basis"
648; and (ii) "even though dolphins strongly associate with longline fishing … the 
Amended Tuna Measure does not allow for a determination that such an association in a fishery is 'regular and significant' such that an observer requirement could be imposed for all tuna that is 
labelled dolphin-safe from that fishery".
649 According to Mexico, these features of the 
determination provisions are "arbitrary".650 In its response to the Panel's question, the 
United States noted that the determination provisions "appropriately provide[] for the possibility  
that the association in the ETP is not unique" and that "other fisheries (such as longline, 
hand line, etc.) may also, like the ETP large purse seine vessel fishery, be so problematic that it 
would be appropriate to require an observer statement to attest to the dolphin safe status of tuna product containing tuna harvested in those fisheries".
651 Further, the United States reiterated its 
view that Mexico "made no claim" that any differ ence between the two types of determinations is 
inconsistent with the covered agreements, and has therefore "made no prima facie  case with 
regard to the determination [provisions]".652 Finally, Mexico connected the features of the 
determination provisions that it had previously characterized as yet another indication of 
"arbitrariness"653 to its argument concerning the "absence of a 'rational connection' between" the 
detrimental impact of the amended tuna measure and the measure's objective.654 
7.181.  Like the Panel, we see the determination prov isions as "an integral part of the certification 
system put in place by the amended tuna measure".655 As such, they are relevant to the analysis 
of whether the United States has brought its dolphin-safe labelling regime into conformity with the recommendations and rulings of the DSB. Furthe rmore, it does not seem to us that the 
United States could have been unaware of the legal issues relating to the role of the determination 
provisions during these Article 21.5 proceedings. In particular, the original panel and Appellate Body reports contain several references to the determination provisions and their 
content.
656 For instance, the original panel observed that it was not aware of any process or 
procedure having been established or initiated, under the US dolphin-safe labelling regime, in order to trigger a determination of regular and significant mortality or serious injury of dolphins.
657 
The Appellate Body also made reference to the determination provisions in connection with its 
discussion of the role that a requirement that an  independent observer certify that no dolphins 
were killed or seriously injured would play in determining whether the dolphin-safe labelling provisions are "calibrated" to the risks arising from fishing techniques other than setting on 
dolphins.
658 In these compliance proceedings, the determination provisions are within the terms of 
reference of the Panel since they were identified by Mexico in its request for the establishment of a panel. Moreover, Mexico identified in its first written submission the determination provisions as 
part of its argument concerning the lack of even-handedness of the certification requirements
659, 
and, as set out above, highlighted key features  relating to the design of the determination 
provisions in response to the Panel's questions and in its comments on the United States' answers. In addition, we also observe that the United States had an opportunity to counter Mexico's 
allegations and to put forward its own arguments on  the design of such provisions. However, the 
United States chose not to do so, and instead maintained that Mexico had "made no prima facie  
case with regard to the determination [provisions]".
660 
                                               
648 Mexico's response to Panel question No. 60, para. 6. (fn omitted) 
649 Mexico's response to Panel question No. 60, para. 7. (fn omitted) 
650 Mexico's response to Panel question No. 60, paras. 6-7. 
651 United States' response to  Panel question No. 60, paras. 9-10. (emphasis original) 
652 United States' response to Panel question No. 60, paras. 15-16. 
653 Mexico's response to Panel ques tion No. 60, paras. 6-7 (referring  to Mexico's comments on the 
United States' response to Panel question No. 59). 
654 Mexico's comments on Unit ed States' response to Panel question No. 60, para. 5. 
655 Panel Report, para. 7.257. 
656 See Original Panel Report, paras. 7.534-7.536, 7.538, 7.543, and 7.614; and Appellate Body Report, 
US – Tuna II (Mexico) , para. 249 and para. 296 and fn 613 thereto. 
657 Original Panel Report, para. 7.543. 
658 Appellate Body Report, US – Tuna II (Mexico) , para. 296 and fn 613 thereto. 
659 See Mexico's first written submission to the Panel, para. 289. 
660 United States' response to Panel question No. 60, para. 16. See also United States' comments on 
Mexico's response to Panel question No. 60, para. 5. WT/DS381/AB/RW 
 
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 7.182.  Based on our review of the Panel record, viewed against the backdrop of the original 
proceedings, we do not consider that the Panel improperly made the case for Mexico in respect of the determination provisions. In the light of the above considerations, we find that the 
United States has failed to establish that the Panel improperly made the case for Mexico by finding 
that, by virtue of the determination provisions , the detrimental impact of the amended tuna 
measure does not stem exclusively from a legitimate regulatory distinction. 
Whether the Panel erred in making its findin gs on the determination provisions based 
solely on their design and not on their application 
7.183.  The United States argues that the Panel erred and applied an incorrect legal analysis by, in 
particular, failing to analyse whether the determination provisions support a finding that the certification requirements "are designed and applied" in an even-handed manner. Rather, 
"the Panel appears to have examined only how the determination provisions are designed  without 
also examining how those provisions are applied ."
661 Thus, according to the United States, there is 
no basis for finding that the application of the determination provisions means that the certification 
requirements are not even-handed "as designed and applied".662 
7.184.  Mexico responds that, in order to determine whether the regulatory distinctions of the 
amended tuna measure are even-handed, the Panel was required to assess the design, 
architecture, revealing structure, operation, and application of the measure. Since the 
determination provisions are an integral part of the amended tuna measure and, as recognized by 
the United States, they have never been applied, it was appropriate – and indeed required – for the Panel to focus on their design, architecture, and revealing structure.
663 Thus, Mexico asserts 
that the United States incorrectly faults the Panel for analysing the "design" of the determination 
provisions alone, instead of also examining how the determination provisions are "applied". Arguing that the United States can point to no evidence that the provisions have been applied, 
Mexico asserts that it was appropriate for the Panel to make findings based on the design of the 
determination provisions.
664 
7.185.  At the outset, we note the Panel's statement that the determination provisions "appear to 
be designed to enable the United States to impose conditions on fisheries other than the ETP large 
purse seine fishery where the conditions in the former approach those of the latter".665 In 
particular, we observe that, in the non-ETP large purse-seine fishery, the existing requirement for 
captain certification in respect of the conditions of "no setting on dolphins" and "no dolphins killed 
or seriously injured" is supplemented by a requirement of observer certification in respect of those 
two conditions when a determination has been made that there is regular and significant tuna-dolphin association, similar to the tuna-dolphin association in the ETP. Moreover, with respect 
to "all other fisheries", the United States' authorities can make a determination that there is 
regular and significant mortality or serious injury in a specific fishery, which would supplement the existing requirement that a captain provide a certification in respect of the condition of 
"no dolphins killed or seriously injured" by requiring the same certification from an observer in 
such a fishery. At the same time, the Panel indicated that the determination provisions do not contemplate the possibility that the US authoritie s make a determination of regular and significant 
mortality within the non-ETP purse-seine fishery, or a determination of regular and significant 
tuna-dolphin association within "all other fisheries".
666 The United States confirmed to the Panel 
that this understanding was correct.667 
7.186.  In advancing this claim, the United States appears to rely on the Appellate Body's 
reasoning that the relevant inquiry "probes the legitimacy of regulatory distinctions through careful 
scrutiny of whether they are designed and applied  in an even-handed manner such that they may 
                                               
661 United States' appellant's submission, para. 231. (emphasis original) 
662 United States' appellant's submission, para. 234 (referring to Panel Report, para. 7.281). 
663 Mexico adds that the determination provisions ar e tied to the United States' argument that the 
amended tuna measure's requirements  for independent observers are "ca librated" to potential harm to 
dolphins. (Mexico's appellee's submission, para. 140) 
664 Mexico's appellee's submission, paras. 145-147. 
665 Panel Report, para. 7.263. The panelist who wrote a separate opinion also cited the determination 
provisions as an example of where the amended tuna measure "enable[s] the United States to impose the 
same requirements in fisheries where the same degree of risk prevails". (Ibid., para. 7.280) 
666 Panel Report, paras. 7.251-7.252. 
667 Panel Report, para. 7.252. WT/DS381/AB/RW 
 
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 be considered 'legitimate' for the purposes of Article 2.1".668 W e  d o  n o t ,  h o w e v e r ,  r e a d  t h i s  
statement to preclude that, depending on the relevant circumstances of a particular case, it may be appropriate for a panel's examination of the measure at issue to focus on its design, rather than also focusing on its application. In the present case, it is uncontested that "no fishery outside 
the ETP has been determined to have a regular and significant association between tuna and 
dolphins similar to the association in the ETP."
669 Similarly, it is uncontested that the 
US authorities have not made a determination that any fishery belonging to the category of "all 
other fisheries" has regular and significant dolphin mortality.670 Yet, we do not regard the absence 
of such determinations as conclusively establishing that the factual circumstances that they contemplate do not exist. Nor does the absenc e of such determinations say anything about 
whether the circumstances that should trigger such determinations are likely to exist in the future. 
For these reasons, we do not see what probative or legal value the United States considers the 
Panel ought to have attached to the "application" of the determination provisions. It follows that, contrary to the United States' position, we do no t consider that, in the present circumstances, a 
focus on the design of the determination provisions per se  renders the Panel's analysis faulty. 
7.187.  The United States contends that the current fishery-by-fishery data clearly supports that 
there is no evidence  to establish that there is currently regular and significant association and 
regular or significant mortality or serious injury in any fishery other than the ETP large purse-seine 
fishery.
671 In criticizing the Panel for not examining how the determination provisions are applied , 
the United States appears to be taking issue with the fact that the Panel never assessed whether the evidence on the record  established that there is currently regular and significant association or 
regular and significant mortality or serious injury in any fishery other than the ETP large 
purse-seine fishery.
672 However, the Panel never sought to scrutinize the evidentiary basis 
supporting the proposition that the US authorities have failed to make a determination as to the 
existence of a fishery, other than the ETP larg e purse-seine fishery, presenting regular and 
significant association or regular and significant mortality or serious injury. Rather, the Panel was focusing on the content, structure, and expected operation of the measure at issue with a view to 
delineating the scope of application of each of the relevant determinations. Therefore, we see as 
somewhat beside the point the United States' assertion that "there is no basis on which to find that the certification requirements, in fact, impose an  observer requirement on tuna product produced 
from Mexican large purse seine vessels operating in the ETP and not on tuna product produced 
from other fisheries 'where, as a matter of fact, the conditions in [that other fishery] are the same 
as those in the ETP large purse seine fishery.'"
673 
7.188.  For the foregoing reasons, we find that the United States has not established that the 
Panel erred in its assessment of whether the determination provisions are even-handed under 
Article 2.1 of the TBT Agreement. 
7.2.3.3  Whether the Panel acted inconsistently with Article 11 of the DSU 
7.189.  Each of the participants raises several claims under Article 11 of the DSU in connection 
with the Panel's analysis of whether the detrimental impact on Mexican tuna products flowing from the eligibility criteria and the certification requirements stems exclusively from a legitimate regulatory distinction. With respect to the Panel's analysis of the eligibility criteria, Mexico raises 
three claims of error under Article 11 of the DSU.  First, Mexico argues that the Panel erred by 
changing the factual findings from the original  proceedings regarding the adverse effects from 
setting on dolphins.
674 Mexico's second challenge under Article 11 of the DSU is that the Panel 
erred in finding that other fishing meth ods have no unobservable adverse effects.675 Third, Mexico 
                                               
668 Appellate Body Reports, US – COOL (Article 21.5 – Canada and Mexico) , para. 5.92. 
(emphasis added) 
669 Panel Report, para. 3.22. 
670 Panel Report, para. 3.22. 
671 United States' appellant's submission, para. 233. 
672 The United States argues that the Panel reache d its conclusion in respect of the determination 
provisions "without any regard for the evidentiary reco rd". (United States' appellant's submission, para. 235) 
673 United States' appellant's submission, para. 234 (quoting Panel Report, para. 7.258). 
674 Mexico's other appellant's subm ission, subheading V.B.2.c(i). 
675 Mexico's other appellant's subm ission, subheading V.B.2.c(ii). WT/DS381/AB/RW 
 
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 contends that the Panel incorrectly asserted that the Appellate Body made a finding that setting on 
dolphins is more harmful to dolphins than other fishing methods.676 
7.190.  As regards the Panel's analysis of the certification requirements, the United States 
contends that the Panel acted inconsistently with Article 11 of the DSU by reaching a finding with 
respect to the determination provisions that is unsupported by the evidence on the record. Mexico, 
in turn, raises two Article 11 claims in connection with this part of the Panel's analysis. First, Mexico argues that the Panel erred in rejecting Mexico's argument and evidence that fishing vessel 
captains have an economic self-interest in not reporting that dolphins were killed or seriously 
injured.
677 Second, Mexico contends that, in finding that setting on dolphins occurs only in the ETP, 
the Panel erred in disregarding evidence that "dolphins associate with tuna and are intentionally set upon in the Indian Ocean."
678 
7.191.  Before turning to these various claims of error on appeal, we recall the legal standard for 
establishing that a panel has acted inconsistently with its duties under Article 11 of the DSU. To comply with its duty to make an objective assessment of the matter before it, the Appellate Body 
has stated that a panel must "consider all the evidence presented to it, assess its credibility, 
determine its weight, and ensure that its factual findings have a proper basis in that evidence".
679 
Panels may not "make affirmative findings that lack a basis in the evidence contained in the panel 
record".680 Within these parameters, panels enjoy a margin of discretion in their assessment of the 
facts.681 This margin includes the discretion to determine how much weight to attach to the various 
items of evidence placed before them by the parties.682 Moreover, the mere fact that a panel did 
not explicitly refer to each and every piece of evidence in its reasoning is insufficient to establish a 
claim of violation under Article 11.683 Rather, a participant must explain why such evidence is so 
material to its case that the panel's failure to address explicitly and rely upon the evidence has a bearing on the objectivity of the panel's factual assessment.
684 The Appellate Body has also 
considered that a participant cannot simply recast factual arguments that it made before the panel 
in the guise of a claim under Article 11.685 Instead, for a claim under Article 11 to succeed, the 
Appellate Body "must be satisfied that the panel has exceeded the bounds of its discretion, as the 
trier of facts".686 "[N]ot every error allegedly committed by a panel amounts to a violation of 
Article 11 of the DSU"687, but only those that are so material that, "taken together or singly"688, 
they undermine the objectivity of the panel's assessment of the matter before it.689 The 
Appellate Body has stated that a claim that a panel has failed to conduct the "objective 
assessment of the matter before it" required by Article 11 of the DSU is "a very serious 
allegation"690, and the Appellate Body will not "interfere lightly"691 with a panel's fact-finding 
authority. 
                                               
676 Mexico's other appellant's subm ission, subheading V.B.2.c(iii). 
677 Mexico's other appellant's submission, para. 139. 
678 Mexico's other appellant's submission, para. 143. 
679 Appellate Body Reports, China – Rare Earths , para. 5.178; Brazil – Retreaded Tyres , para. 185;  
EC – Hormones , paras. 132-133; Australia – Salmon , para. 266; EC – Asbestos , para. 161; EC – Bed Linen 
(Article 21.5 – India) , paras. 170, 177, and 181; EC – Sardines , para. 299; EC – Tube or Pipe Fittings , 
para. 125; Japan – Apples , para. 221; Japan – Agricultural Products II , paras. 141-142; Korea – Alcoholic 
Beverages , paras. 161-162; Korea – Dairy , para. 138; US – Carbon Steel , para. 142; US – Gambling , 
para. 363; US – Oil Country Tubular Goods Sunset Reviews , para. 313; EC – Selected Customs Matters , 
para. 258. 
680 Appellate Body Reports, US – Carbon Steel , para. 142; US – Wheat Gluten , paras. 161-162. 
681 Appellate Body Reports, China – Raw Materials , para. 341; EC – Asbestos , para. 161;  
EC – Hormones , para. 132; EC – Sardines , para. 299; Japan – Apples , paras. 221-222; Korea – Dairy , 
paras. 137-138; US – Wheat Gluten , para. 151. 
682 Appellate Body Report, Korea – Dairy , para. 137. 
683 Appellate Body Report, EC – Fasteners (China) , para. 441 (referring to Appellate Body Report, 
Brazil – Retreaded Tyres , para. 202). 
684 Appellate Body Report, EC – Fasteners (China) , para. 442. 
685 Appellate Body Report, EC – Fasteners (China) , para. 442. 
686 Appellate Body Report, US – Wheat Gluten , para. 151. 
687 Appellate Body Report, EC – Fasteners (China) , para. 442. 
688 Appellate Body Report, EC and certain member States – Large Civil Aircraft , para. 1318. 
689 Appellate Body Reports, China – Rare Earths , para. 5.179. 
690 Appellate Body Reports, US – Carbon Steel (India) , para. 4.79; China – Rare Earths , para. 5.227; 
EC – Poultry , para. 133. 
691 Appellate Body Reports, EC – Sardines , para. 299; US – Wheat Gluten , para. 151; US – Carbon 
Steel, para. 142. WT/DS381/AB/RW 
 
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 7.192.  As noted above, Mexico raises three claims of error under Article 11 of the DSU relating to 
the Panel's application of the "less favourable treatment" test to the eligibility criteria. Mexico's first challenge under Article 11 of the DSU is that the Panel erred in "changing" the factual findings regarding setting on dolphins from the original proceedings. In particular, Mexico claims that the 
original panel's findings that setting on dolphins in the ETP causes unobserved harms to dolphins 
were "not as strong" in the original proceedings as the Panel now asserts them to be.
692 Mexico 
points out that the original panel had found that: 
… it appears that there is a degree of uncertainty in relation to the extent to which 
setting on dolphins may have an advers e impact on dolphins beyond observed 
mortality. Nonetheless, we consider that sufficient evidence has been put forward by the United States to raise a presumption that genuine concerns exist in this respect.
693 
7.193.  According to Mexico, even though there wa s no new evidence on the unobserved effects of 
setting on dolphins in the ETP in these Article 21.5 proceedings, the Panel converted the prior finding that "genuine concerns" exist regarding th e extent to which setting on dolphins may have 
an adverse impact on dolphins beyond observed mortality into a finding of "conclusive evidence" of 
significant unobserved effects.
694 
7.194.  The United States responds that the Panel did not "change" the finding concerning the 
unobserved harms caused by dolphin sets from the original proceedings, nor mischaracterize the 
finding of the original panel in this regard. The United States adds that the Panel accurately concluded that the original panel made definitive findings that setting on dolphins can cause adverse effects on dolphins apart from observed mortalities.
695 According to the United States, the 
Appellate Body confirmed the original panel's analysis that dolphins suffer adverse impact beyond 
observed mortalities from setting on dolphins.696 
7.195.  We begin by noting that Mexico does not identify any specific paragraph in the 
Panel Report where the Panel allegedly "changed" the factual findings made by the original panel 
regarding the unobserved adverse effects on dolphi ns from setting on dolphins. From the context 
of Mexico's submission, we understand this allegation to relate to the findings made by the Panel 
in paragraphs 7.120 through 7.122 of its Report. In these paragraphs, the Panel made several 
observations regarding the unobserved adverse effe cts of setting on dolphins. According to the 
Panel, the Appellate Body "found that setting on dolphins is 'particularly harmful to dolphins'".697 
The Panel quoted various adverse effects "beyond observed mortalities" that can arise from setting 
on dolphins.698 The Panel also indicated that, "[i]mportantly, the Appellate Body also accepted that 
these harms arise as a result of the 'chase itself'."699 The Panel observed that, as a consequence, 
"[the Appellate Body] affirmed the original panel's conclusion that 'the US objectives … to minimize 
unobserved consequences of setting on dolphins' would not be attainable if tuna caught by 
setting-on dolphins were eligible for the dolphin-safe label".700 Then, the Panel expressed its 
understanding that "the Appellate Body clearly foun d that setting on dolphins causes observed and 
unobserved harm to dolphins."701  
7.196.  Mexico claims that "[t]he original panel's findings that dolphin sets in the ETP cause 
unobserved harms to dolphins were not as strong in the original proceedings as the Panel now asserts them to be."
702 In this regard, we consider it important to clarify that, in paragraphs 7.120 
                                               
692 Mexico's other appellant's submission, para. 117. 
693 Mexico's other appellant's submission, para. 117 (quoting Original Panel Report, para. 7.504). 
(underlining added by Mexico) 
694 Mexico's other appellant's submission, para. 118. 
695 The United States points out that  "the finding of the original pane l was that 'various adverse impacts 
can arise from setting on dolphins, beyond observed mortal ities.'" The United States also indicates that "the 
original panel had found that, while there was some unce rtainty regarding 'the exte nt' of these impacts, the 
U.S. evidence had established a presumption that 'genui ne concerns exist' in that respect." (United States' 
appellee's submission, para. 109 (quoting Original Panel Report, para. 7.737)) 
696 United States' appellee's submission, paras. 110-111. 
697 Panel Report, para. 7.120 (quoting Appellate Body Report, US – Tuna II (Mexico) , para. 289). 
698 Panel Report, para. 7.120 (quoting, without attribution, Original Panel Report, para. 7.499). 
699 Panel Report, para. 7.121. 
700 Panel Report, para. 7.121 (quoting Original Panel Report, para. 7.613). 
701 Panel Report, para. 7.122. 
702 Mexico's other appellant's submission, para. 117.  WT/DS381/AB/RW 
 
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 through 7.122 of its Report, the Panel was not referring to the findings of the original panel, but 
was rather describing its understanding of the findings reached by the Appellate Body in the original proceedings. In any event, the Panel's references to the Appellate Body report do not, in our view, mischaracterize the findings made in the original proceedings regarding the existence of 
unobserved effects on dolphins. We recall that, in a subsection of its report entitled "Uncontested 
Findings by the Panel", the Appellate Body made the following observations:  
The [original panel] further remarked that "there is a degree of uncertainty in relation 
to the extent to which setting on dolphins may have an adverse impact on dolphins 
beyond observed mortality." Nonetheless,  the [original panel] determined "that 
sufficient evidence has been put forward by the United States to raise a presumption 
that genuine concerns exist in this respect". The [original panel] also found that the 
United States had put forward sufficient evidence to raise a presumption "that the 
method of setting on dolphins 'has the capacity' of resulting in observed and 
unobserved adverse effects on dolphins".
703 
7.197.  The Appellate Body report also shows that, in response to questioning at the oral hearing 
in the original proceedings, Mexico accepted that "setting on dolphins within the ETP … has the capacity of resulting in observed and unobserved  effects on dolphins".
704 It follows that, in our 
view, the Panel reiterated the substance of the Appellate Body's findings when it indicated that 
"the Appellate Body clearly found that setting on dolphins causes observed and unobserved harm to dolphins."
705 Therefore, we do not agree with Mexico that the Panel's findings regarding the 
unobserved harms to dolphins due to setting on dolphins are somehow "stronger" than in the 
original proceedings, or that the Panel breached Article 11 of the DSU in reaching them. 
7.198.  Mexico's second challenge under Article 11 of the DSU is that the Panel erred in finding 
that fishing methods other than setting on dolphins have no unobservable adverse effects. 
According to Mexico, in paragraphs 7.132 and 7.134 of its Report, the Panel found that all of the 
effects on dolphins caused by other fishing meth ods would be "observable" if a trained person 
were watching for them. In Mexico's view, this is a factual error, given that it had submitted 
evidence that not all effects are observable.706 In particular, Mexico argues that the Panel ignored 
evidence presented by Mexico regarding gillnet and longline fishing showing that not all the effects 
from fishing techniques other than setting on dolphins are observable.  
7.199.  In response, the United States argues th at the Panel did not err in finding that other 
fishing methods do not have unobservable effects similar to those associated with setting on 
dolphins in the ETP. Contrary to Mexico's argument, the Panel's in-depth examination of the evidence on this point clearly satisfied its obligations under Article 11 of the DSU. The Panel's 
finding that fishing methods, other than setting on dolphins, do not cause "the kinds of 
unobservable harms that are caused by setting on dolphins"
707 is amply supported by evidence on 
the record and reflects a weighing and balancing of that evidence in line with Article 11.  
7.200.  We begin by noting that the essence of Mexico's claim is that the Panel erred in finding 
that other fishing methods have no unobservabl e adverse effects. This, however, is not an 
accurate characterization of the findings made by the Panel. Contrary to Mexico's assertion, the Panel did not make a finding that all of the effects on dolphins of other fishing methods would be 
"observable" if a trained person were watching for them. Rather, in paragraph 7.132, the Panel 
found that none of the evidence presented by Mexico regarding the adverse effects on dolphins caused by other fishing methods "suggests that fishing methods other than setting on dolphins 
inflict the same kinds of unobservable harms that are caused by net sets" (i.e. setting on 
dolphins).
708 In paragraph 7.134, the Panel rejected Mexico's contention that the United States 
had conceded that "fishing methods other than setting on dolphins cause the kind of unobservable 
harms that dolphins suffer as a 'result of the chase in itself'."709 Therefore, contrary to Mexico's 
assertion, we do not read the Panel's reasoning to include any finding that all of the adverse 
                                               
703 Appellate Body Report, US – Tuna II (Mexico) , para. 246. (fns omitted) 
704 Appellate Body Report, US – Tuna II (Mexico) , para. 251. (emphasis adde d; fn omitted) See also 
fn 513 to para. 246. 
705 Panel Report, para. 7.122. 
706 Mexico's other appellant's submission, paras. 120-121. 
707 Panel Report, paras. 7.131 and 7.134.  
708 Panel Report, para. 7.132. 
709 Panel Report, para. 7.134. WT/DS381/AB/RW 
 
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 effects on dolphins caused by other fishing meth ods would be "observable" if a trained person 
were watching for them. 
7.201.  Moreover, we note that, in raising this cl aim of error under Article 11 of the DSU, Mexico 
appears to be rearguing the case that it put to th e Panel and asking us to attribute to its evidence 
greater significance than did the Panel. Such a request is neither compatible with the scope of 
appellate review, nor a proper way to esta blish a breach of Article 11 of the DSU.710 In any event, 
we disagree with Mexico's assertion that the Panel "did not even mention" the evidence concerning 
the adverse effects on dolphins caused by fishing using gillnets and longlines.711 Our review of the 
Panel Report reveals, rather, that the Panel did examine evidence regarding gillnet fishing, in 
paragraph 7.130, and evidence on longline fishing, in paragraph 7.131 of its Report. 
7.202.  For the foregoing reasons, we consider that Mexico has not properly substantiated its claim 
under Article 11 of the DSU, nor established that the Panel found that fishing methods other than 
setting on dolphins have no unobservable adverse effects. 
7.203.  In its third challenge under Article 11 of the DSU, Mexico asks us to reverse the Panel's 
finding that the Appellate Body made a factual finding that "dolphin sets under the rules of [the] 
AIDCP are more harmful to dolphins than other fishing methods."712 In making its arguments on 
this issue, Mexico refers to the following statement by the Panel: 
The Appellate Body found that setting on dolphins is "particularly harmful to dolphins", 
because: 
[V]arious adverse impacts can arise from setting on dolphins, beyond 
observed mortalities, including cow-calf separation during the chasing and 
encirclement, threatening the subsistence of the calf and adding 
casualties to the number of observed moralities [sic], as well as muscular damage, immune and reproductive system failures, and other adverse 
health consequences.
713 
7.204.  Mexico highlights that the quoted text that the Panel attributed to the Appellate Body is 
actually a quotation from the original panel report, which does not appear in the Appellate Body 
report. Mexico also refers to paragraph 260 of the Appellate Body report, where the 
Appellate Body noted that the original panel had distinguished between the risks associated with 
setting on dolphins before the AIDCP controls were adopted  (unregulated dolphin sets), and 
dolphin sets that are regulated under the rules of the AIDCP. On this basis, Mexico argues that, 
when read in context, "the Appellate Body did not find, nor did it imply, that [setting on dolphins] 
is more harmful to dolphins than other fishing methods when the dolphin set method is regulated under the AIDCP."
714 To the contrary, Mexico considers that the Appellate Body affirmed the 
finding of the original panel that dolphins face "equivalent" risks from AIDCP-regulated setting on 
dolphins and from other fishing methods.715 
7.205.  The United States rejects Mexico's claims of error. In its view, the original proceedings 
clearly resolved that setting on dolphins, including under the AIDCP regime, causes various 
adverse impacts "beyond observed mortalities". Moreover, "it is clear from the Appellate Body report that the finding that setting on dolphins is 'particularly harmful to dolphins' was not limited to setting on dolphins other than under the AIDCP regime."
716  
7.206.  In addressing Mexico's third challenge und er Article 11 of the DSU, we begin by pointing 
out that the paragraph of the Panel Report to which Mexico objects is silent as to the relative 
harms  associated with setting on dolphins, on the one hand, as compared to other fishing 
methods, on the other hand. Rather, in the paragraph identified by Mexico, the Panel is addressing 
                                               
710 Appellate Body Report, EC – Fasteners (China) , para. 442. 
711 Mexico's other appellant's submission, paras. 121-122. 
712 Mexico's other appellant's submission, para. 130. 
713 Mexico's other appellant's submission, pa ra. 125 (quoting Panel Report, para. 7.120). 
714 Mexico's other appellant's submission, para. 129. 
715 Mexico's other appellant's submission, para . 129 (referring to Appellate Body Report, US – Tuna II 
(Mexico) , paras. 260-281). 
716 United States' appellee's submission, para. 128. WT/DS381/AB/RW 
 
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 only the fishing method of setting on dolphins. The Panel's language is somewhat unfortunate 
insofar as it may be read to imply that the Appellate Body, itself, "found" that setting on dolphins is "particularly harmful to dolphins".
717 What the Appellate Body actually stated, as Mexico also 
points out718, was that the original panel appeared to have "accepted the United States' argument 
that the fishing technique of setting on dolphins is particularly harmful to dolphins".719 Moreover, 
while Mexico is correct that the passage quoted by  the Panel comes from the original panel report 
rather than the Appellate Body report, we do not see that this alone amounts to error under 
Article 11, particularly given that the Appellate Bo dy did refer to precisely these types of harms in 
its report. Specifically, in addressing the United States' appeal under Article 2.2 of the TBT Agreement, the Appellate Body took note of the original panel's finding, "undisputed by the 
participants, that dolphins suffer adverse impact beyond observed mortalities from setting on 
dolphins, even under the restrictions contained in the AIDCP rules."
720 In footnotes to this 
observation, the Appellate Body also referred to the original panel's statements regarding the unobserved effects that arise "as a result of the chase itself"
721 and to the examples given by the 
original panel of these various adverse effects.722  
7.207.  We see no merit in this allegation of error under Article 11 of the DSU by Mexico. Mexico 
has neither established that the Panel made a find ing "that the dolphin set method is more harmful 
to dolphins than other fishing methods when the dolphin set method is regulated under the 
AIDCP", nor identified any problem with the statements made by the Panel regarding the Appellate Body's use of the phrase "particularly harmful" in connection with the fishing method of setting on dolphins. We further observe that Mexico's arguments in support of this claim of error 
are cursory and do not explain why any alleged e rror made by the Panel would rise to the level 
required in order to establish a breach of Article 11 of the DSU.  
7.208.  For all of the above reasons, we find that Mexico has not established that the Panel acted 
inconsistently with its duty to conduct an ob jective assessment of the matter, pursuant to 
Article 11 of the DSU, in its analysis of the consistency of the eligibility criteria set out in the amended tuna measure with Article 2.1 of the TBT Agreement. 
7.209.  We next examine the participants' claims in connection with the Panel's analysis of the 
certification requirements. We begin with the United States' claim that the Panel acted inconsistently with Article 11 of the DSU in its assessment of the determination provisions. 
7.210.  The United States contends that the Panel acted inconsistently with Article 11 of the DSU 
by arriving at a finding that is unsupported by the evidence on the record. The United States 
recalls that the Panel expressed concern over two particular "gaps" in the determination provisions.
723 The first "gap" identified by the Panel would occur within the non-ETP purse-seine 
fishery where there is regular and significant mortality or serious injury of dolphins without regular 
and significant tuna-dolphin association. The United States notes that the evidence establishes that there is a direct positive correlation between association and observed mortality or serious 
injury in purse-seine fisheries. As a consequence, "the evidence establishes that a 'gap' such as 
the Panel envisioned does not, in fact, occur – there is no evidence on the record that a 
purse seine fishery exists where a 'regular and significant' mortality is occurring without a tuna-dolphin association also being present."
724 The United States indicates that, in the Panel's 
view, the second "gap" would occur in a non-purse-seine fishery where there is regular and 
significant tuna-dolphin association without regular and significant mortality or serious injury of dolphins. The United States considers that the Panel's analysis appears to be a "self-defeating 
                                               
717 Panel Report, para. 7.120 (quoting Appellate Body Report, US – Tuna II (Mexico) , para. 289). 
718 Mexico's other appellant's submission, para. 126. 
719 Appellate Body Report, US – Tuna II (Mexico) , para. 289. 
720 Appellate Body Report, US – Tuna II (Mexico) , para. 330 (referring to Original Panel Report, 
paras. 7.491-7.506). 
721 Appellate Body Report, US – Tuna II (Mexico) , fn 664 to para. 330 (quoting Original Panel Report, 
para. 7.504). 
722 The Appellate Body noted the following examples gi ven by the original panel of the various adverse 
effects that arise "as a result of the chase in itself": "cow-calf separation; potential muscle injury resulting from 
the chase; immune and reproductive systems failures; and other adverse health co nsequences for dolphins, 
such as continuous acute stress". (Appellate Body Report, US – Tuna II (Mexico) , fn 663 to para. 330 (referring 
to Original Panel Report, paras. 7.491-7.506)) 
723 United States' appellant's submission, paras. 237-239. 
724 United States' appellant's submission, para. 245. WT/DS381/AB/RW 
 
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 proposition"725, because, if the Panel is correct that the risk of mortality or serious injury is 
positively correlated with the existence of a tuna-dolphin association in non-purse-seine fisheries, then any regular and significant association would imply that there is regular and significant mortality or serious injury. In such situation, "the non-purse seine fishery would not fall into a 
'gap' at all but would be designated under [Section] 216.91(a)(4)(iii)."
726 
7.211.  Mexico disagrees with the United States' argument that the Panel acted inconsistently with 
Article 11 of the DSU by finding that there are tw o "gaps" in the determination provisions. Mexico 
argues that there is considerable evidence on  the record to support the Panel's findings.727 
Moreover, in Mexico's view, it was "both reasonable and appropriate for the Panel to conclude that dolphin association with fishing methods other than purse seine nets could be harmful to dolphins, and that purse seine fishing could cause dolphin mortalities even if an ocean region did not feature 
tuna-dolphin association similar to the ETP".
728 
7.212.  We understand the essence of the United States' claim to be that the Panel's reasoning 
and findings regarding the determination provisions  were not based on "sufficient" evidence and, 
consequently, that the Panel acted inconsistently with Article 11 of the DSU in making such 
findings. The United States contends that it is incorrect to believe that there are two "gaps" in the determination provisions. 
7.213.  Our assessment of the United States' arguments reveals that a number of them are aimed 
at establishing that there is no evidence  on the record supporting the conclusion that there is any 
fishery, other than the ETP large purse-seine fi shery, where there is regular and significant 
tuna-dolphin association or regular and significant mortality or serious injury of dolphins. We have 
examined and rejected this argument above in th e context of the United States' challenge to the 
Panel's application of Article 2.1 to the determination provisions. We recall that the Panel never sought to scrutinize the evidentiary basis supporti ng the proposition that the US authorities have 
failed to make a determination as to the existence of a fishery, other than the ETP large 
purse-seine fishery presenting regular and significant tuna-dolphin association or regular and significant mortality or serious injury of dolphins. Rather, the Panel was focusing on the content, 
structure, and expected operation of the measure at issue with a view to delineating the scope of 
application of each of the relevant determinations. The Panel was thus providing a series of hypothetical situations regarding the applicability of the determination provisions to the various fisheries that are subject to the amended tuna measure. 
7.214.  In the light of the above considerations, we  find that the United States has not established 
that the Panel acted inconsistently with its duty to conduct an objective assessment of the matter 
before it pursuant to Article 11 of the DSU in its analysis of the consistency of the determination 
provisions set out in the amended tuna meas ure with Article 2.1 of the TBT Agreement. 
7.215.  We now turn to Mexico's claims that the Panel acted inconsistently with its obligations 
under Article 11 of the DSU in its analysis of the certification requirements under Article 2.1 of the 
TBT Agreement. In its first claim, Mexico asserts that the Panel erred in rejecting Mexico's 
argument and evidence that fishing vessel captains have an economic self-interest in not reporting that dolphins were killed or seriously injured.
729 Mexico asserts that, despite its finding that "[t]he 
documents submitted by Mexico certainly suggest that there have been instances in which 
captains' certifications have been unreliable"730, the Panel declined to "draw the inevitable 
conclusions from that evidence".731 Consequently, Mexico submits that the Panel did not make an 
                                               
725 United States' appellant's submission, para. 247. 
726 United States' appellant's submission, para. 247. 
727 Mexico recalls that the panel in the original proc eedings found that there is "strong evidence that 
regular and significant mortality and serious injury of dolphins also exists outside the ETP". (Mexico's appellee's submission, para. 149 (quoting Original Panel Report, pa ra. 7.543)) Mexico also points to evidence about the 
harms caused to dolphins by other fishing methods, such  as the undisputed facts that dolphins are attracted to 
feed on the fish caught on hooks or in gillnets, an d that the USDOC has designated the Atlantic Pelagic 
Longline fishery as a "Category I" fishery due to frequ ently documented interactio ns with marine mammals. 
(Ibid., para. 149 (referring to Mexico's firs t written submission to the Panel, para. 141)) 
728 Mexico's appellee's submission, para. 151. 
729 Mexico's other appellant's submission, para. 139. 
730 Mexico's other appellant's submission, para. 139 (q uoting Panel Report, para. 7.209; and referring to 
para. 7.596). 
731 Mexico's other appellant's submission, para. 139. WT/DS381/AB/RW 
 
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 objective assessment of the matter "because it conf lated captains' reliability in general with the 
reliability, specifically, of captains' self-certifications with respect to the 'dolphin-safe' status of tuna for the purposes of accessing the market ad vantage of the U.S. label", and requests us to 
reverse the Panel's finding that "captains' dolphin-safe certifications are always reliable."
732 
7.216.  In response, the United States asserts that the Panel's findings regarding the reliability of 
captains' certifications were not inconsistent with Article 11 of the DSU. For the United States, Mexico wrongly argues that the Panel failed to understand that Mexico's argument concerned the 
specific situation of captains making dolphin-sa fe certifications. To the contrary, "the Panel 
described Mexico's argument as relating to vessel captains' 'financial incentive to certify that their catch is dolphin-safe even when it is not'".
733 The United States also disagrees that the Panel erred 
by finding that Mexico had not established that captains' statements are unreliable, because the 
Panel's finding "was supported by a significant am ount of evidence on the record, which Mexico 
f a i l s  t o  c o n f r o n t  i n  m a k i n g  t h i s  a p p e a l " .734 The United States points out that Mexico "does not 
articulate any basis for finding that the Panel exceeded its discretion as the trier of fact, or that the 
Panel's finding was not based on a weighing of the evidence before it", or "allege that the Panel's 
treatment of the evidence undermined its objectivity".735 Consequently, the United States 
concludes that Mexico's claim should be rejected. 
7.217.  At the outset, we note that, in response to questioning at the oral hearing, Mexico 
indicated that this claim is both a challenge to the Panel's application of the law to the facts and a challenge that the Panel acted inconsistently with its obligations under Article 11 of the DSU. We recall that the Appellate Body has stated that, "[i]n most cases … an issue will either  be one of 
application of the law to the facts or an issue of the objective assessment of facts, and not 
both."
736 Allegations implicating a panel's assessment of the facts and evidence fall under 
Article 11 of the DSU.737 Mexico's central argument is that the Panel did not make "an objective 
assessment" because it "declined to draw the inevitable conclusions from [certain] evidence"738 
and because it "conflated captains' reliability in general with the reliability, specifically, of captains' self-certifications with respect to the 'dolphin-safe' status of tuna".
739 In the light of the nature of 
Mexico's arguments, which relate, in our view, to the Panel's weighing of the evidence, we analyse 
Mexico's claim as a challenge to the Panel's findings under Article 11 of the DSU.  
7.218.  Having made this preliminary observation, we also note that Mexico requests us to reverse 
the Panel's finding that "captains' dolphin-safe certifications are always reliable."740 Our review of 
the Panel Report reveals that, in fact, the Panel made no such finding. Rather, after examining the 
arguments and evidence submitted by each party, the Panel considered the evidence presented by 
the United States to be a "highly relevant and probative fact" that "many regional and 
international organizations and arrangements rely on captains' certifications and logbooks".741 In 
the Panel's view, this fact raised "a strong presumption that, from a systemic perspective, such certifications are reliable."
742 Then, the Panel explicitly acknowledged that Mexico's evidence 
"suggest[ed] that there have been instances in which captains' certifications have been 
unreliable".743 However, the Panel noted that this evidence did not suffice to rebut the 
United States' general demonstration regarding the reliability of captains' certifications.744 
                                               
732 Mexico's other appellant's submission, para. 142. 
733 United States' appellee's submission, para. 142 (quoting Panel Report, para. 7.198). 
734 United States' appellee's submission, para. 145. 
735 United States' appellee's submission, para. 147. (fns omitted) 
736 Appellate Body Report, US – Large Civil Aircraft (2nd complaint) , para. 955 (quoting Appellate Body 
Report, EC and certain member States – Large Civil Aircraft , para. 872 (emphasis original)). 
737 Appellate Body Report, US – Large Civil Aircraft (2nd complaint) , para. 955. 
738 Mexico's other appellant's submission, para. 139. 
739 Mexico's other appellant's submission, para. 142. 
740 Mexico's other appellant's submission, para. 142. 
741 Panel Report, para. 7.208. 
742 Panel Report, para. 7.208. 
743 Panel Report, para. 7.209. 
744 In particular, the Panel conclude d that "the fact that domestic, regional, and international regimes 
have continued to rely on captains' certifications and logbooks even though instances of non-compliance have 
been reported suggests … that such instances of non-compliance should not be considered as seriously undermining the general reliability of captains' certifications". (Panel Report, para. 7.209) WT/DS381/AB/RW 
 
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 Furthermore, the Panel was also not convinced by Mexico's argumentation concerning the 
economic incentives facing captains.745 
7.219.  As established by the Appellate Body, panels enjoy a margin of discretion in their 
assessment of the facts under Article 11 of the DSU.746 A panel does not err simply because it 
declines to accord to the evidence the weight that one of the parties believes should be accorded 
to it.747 In the present claim, Mexico does not single out any particular exhibit that the Panel 
misinterpreted or failed to take into consideration. Nor does Mexico point to any mistakes 
regarding the Panel's objectivity in its assessment of the evidence. Consequently, we consider that 
Mexico has not established that the Panel acted inconsistently with Article 11 of the DSU in concluding that "Mexico ha[d] not met its burden of making a prima facie  case that captains' 
certifications are unreliable because captains have a financial incentive not to report accurately on 
the dolphin-safe status of tuna".
748 
7.220.  In its second claim under Article 11 of the DSU, Mexico argues that the Panel erred in its 
finding that setting on dolphins only occurs in the ETP.749 According to Mexico, "[t]he failure of the 
Panel to even mention, let alone address, evidence Mexico submitted that dolphins associate with 
tuna and are intentionally set upon in the Indian Ocean was inconsistent with the Panel's obligations under Article 11 of the DSU".
750 Mexico points out that Exhibit MEX-161 was not 
mentioned or addressed by the Panel.751 According to Mexico, Exhibit MEX-161, a report by 
Dr R. Charles Anderson on Cetaceans and Tuna Fisheries in the Western and Central Indian 
Ocean752, contains a comprehensive and scientific analysis of dolphin mortalities in the 
Indian Ocean tuna fishery.753 Mexico submits that "the refusal of the Panel to deal with this crucial 
evidence played a key role in its finding that independent observers are unnecessary outside the 
ETP to assure the accuracy of dolphin-safe claims."754 
7.221.  The United States rejects Mexico's appeal and asserts that "Mexico has failed to meet the 
high standard required for a successful Article 11 claim".755 The United States argues, first, that 
the Panel fulfilled its obligations under Article 11 since it analysed Mexico's evidence and arguments concerning the existence of dolphin sets outside the ETP.
756 The United States points 
out that Exhibit MEX-161 was acknowledged by the Panel in a citation in another part of the 
Panel Report.757 Accordingly, the Panel "had discretion to choose 'which evidence … to utilize in 
making findings' and the fact that it did not rely on  one of Mexico's exhibits in a particular place is 
not sufficient to establish an Article 11 violation."758 The United States submits that, in any event, 
Exhibit MEX-161 in "no way undermines the Panel's finding", since the report in this exhibit makes 
no mention of "dolphins sets, as they occur in the ETP – involving chasing dolphins to catch tuna – ever occurring outside  the ETP" and does not suggest that "the type of 'association' that ETP large 
purse seiners exploit … occurs anywhere outside the ETP".
759 
                                               
745 For the Panel, Mexico provided no evidence to esta blish that it is unlikely that captains accurately 
report dolphin mortality or serious injury. (Panel Report, para. 7.210) 
746 Appellate Body Reports, China – Raw Materials , para. 341; EC – Asbestos , para. 161;  
EC – Hormones , para. 132; EC – Sardines , para. 299; Japan – Apples , para. 221; Korea – Dairy , 
paras. 137-138; US – Wheat Gluten , para. 151. 
747 Appellate Body Reports, Australia – Salmon , para. 267; Japan – Apples , para. 221; Korea – Alcoholic 
Beverages , para. 164. 
748 Panel Report, para. 7.211. 
749 Mexico notes that the Panel rejected its position, stating that, "although dolphins may occasionally 
and incidentally be set on outside the ETP, it is only inside the ETP that setting on dolphins is practiced consistently or 'systematically'". (Mexico's other appellant's submission, para. 143 (quoting Panel Report, para. 7.242)) 
750 Mexico's other appellant's submission, para. 143. 
751 Mexico's other appellant's submission, paras. 144-145. 
752 R.C. Anderson, Cetaceans and Tuna Fisheries in the Western and Central Indian Ocean , International 
Pole and Line Foundation, Technical Report No. 2 (London, 2014) (Panel Exhibit MEX-161). 
753 Mexico's other appellant's submission, paras. 143-144. 
754 Mexico's other appellant's submission, para. 146. 
755 United States' appellee's submission, para. 160. 
756 United States' appellee's submission, para. 156 (r eferring to Panel Report, fn 134 to para. 7.46). 
757 United States' appellee's submission, para. 156 (r eferring to Panel Report, fn 134 to para. 7.46). 
758 United States' appellee's submission, para. 156 (quoting Appellate Body Reports, China – Rare 
Earths , para. 5.178). 
759 United States' appellee's submissi on, para. 159 (referring to Anderson, Cetaceans and Tuna 
Fisheries ). (emphasis original) WT/DS381/AB/RW 
 
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 7.222.  Mexico's central claim on appeal is that the Panel failed to address the evidence contained 
in Exhibit MEX-161, which, in its view, indicates that dolphins associate with tuna and are intentionally set upon in the Indian Ocean. According to Mexico, this amounts to a breach of the Panel's obligations under Article 11 of the DSU. 
7.223.  At the outset, we observe that Mexico co rrectly points out that the Panel did not discuss 
Exhibit MEX-161 in the section of the Panel Report addressing the certification requirements.
760 
However, this does not necessarily amount to a breach of the Panel's obligations under Article 11 
of the DSU. As established by the Appellate Body, the mere fact that a panel did not explicitly refer 
to each and every piece of evidence in its reasonin g is insufficient to establish a claim of violation 
under Article 11.761 Indeed, it is within the Panel's discretion in assessing the facts "to decide 
which evidence it chooses to utilize in making findings"762 and to determine how much weight to 
attach to the various items of evidence placed before it by the parties.763  
7.224.  Moreover, we observe that the content of Exhibit MEX-161 is entirely compatible with the 
Panel's findings. Indeed, we note that, before the Panel, Mexico argued that "'tuna dolphin 
associations have been sighted and deliberately set on' outside of the ETP, and accordingly the 
absence of independent observers outside the ETP is unjustifiable."764 After reviewing evidence 
submitted by both parties, the Panel was not pe rsuaded by Mexico's arguments and evidence. We 
note that, in response to Mexico's argument, th e Panel acknowledged that the evidence submitted 
by Mexico suggests that "there may be some interaction between tuna and marine mammals, including dolphins, outside of the ETP".
765 However, the Panel also pointed out that "dolphins in 
the Atlantic, Indian, and western Pacific Oceans [do not associate with tuna] as systematically as 
they do in the Eastern Tropical Pacific".766 This passage reveals that the Panel did acknowledge 
and accept the existence of association between tuna and dolphins in the Indian Ocean, which is one of the issues addressed in Exhibit MEX-161. Furthermore, we observe that, while this exhibit 
concludes that "dolphins and tuna do associate in the [Western Indian Ocean (WIO)]"
767, it also 
notes that "the only comparative study of the cetaceans from the [WIO] and the ETP … suggested 
that tuna-dolphin schools were seen less frequently in the WIO than in the ETP."768 This 
observation from Exhibit MEX-161 also seems to be in line with the above-mentioned Panel 
findings.  
7.225.  Furthermore, we note that the Panel indicated that, "although dolphins may occasionally 
and incidentally be set on outside the ETP, it is only inside the ETP that setting on dolphins is 
practiced consistently or 'systematically'".769 This passage shows that, contrary to Mexico's 
assertion, the Panel never made the finding that "dolphin sets are only made in the ETP".770 To the 
contrary, the Panel acknowledged that setting on dolphins may, "occasionally and incidentally", 
occur outside the ETP. Exhibit MEX-161 notes that "it is possible that there has been more setting 
on dolphins in the WIO than has been reported".771 At the same time, this exhibit also indicates 
that "[t]his does not imply that the tuna-dolphin fishery in the WIO is of the same scale as that in 
                                               
760 We note that the Panel did acknow ledge the existence of Exhibit MEX-161, given that it referred to it 
in a different part of its Report. (Panel Report, fn 134 to para. 7.46) We observe, however, that this reference by the Panel did not relate to the issue of the prevalen ce of tuna-dolphin association and setting on practices 
outside the ETP, but was rather utilized to support the proposition that there is limited evidence regarding the 
incidence of dolphin mortality in fisheries other than the ETP large purse-seine fishery. (Ibid.) 
761 Appellate Body Report, EC – Fasteners (China) , paras. 441-442; Brazil – Retreaded Tyres , para. 202. 
762 Appellate Body Report, EC – Hormones , para. 135. 
763 Appellate Body Report, Korea – Dairy , para. 137. 
764 Panel Report, para. 7.241 (quoting Mexico's firs t written submission to the Panel, para. 113). 
765 Panel Report, para. 7.241. 
766 Panel Report, para. 7.241 (quoting National Marine Fisheries Service, An Annotated Bibliography of 
Available Literature Regarding Cetacean Interactions wi th Tuna Purse-Seine Fisheries Outside of the Eastern 
Tropical Pacific Ocean , Administrative Report LJ-96-20 (November 1996) (Panel Exhibit MEX-40), p. 2). 
767 Mexico's other appellant's submis sion, para. 145 (quoting Anderson, Cetaceans and Tuna Fisheries , 
p. 63). 
768 Mexico's other appellant's submission, para. 145;  United States' appellee's submission, para. 158 
(both quoting Anderson, Cetaceans and Tuna Fisheries , p. 63). 
769 Panel Report, para. 7.242. 
770 Mexico's other appellant' s submission, heading VI.B. 
771 Mexico's other appellant's submis sion, para. 145 (quoting Anderson, Cetaceans and Tuna Fisheries , 
p. 67). WT/DS381/AB/RW 
 
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 the ETP."772 The study concludes that "[t]he true scale of purse seine fishing on dolphin-associated 
schools in the WIO is therefore open to question."773 These passages, in our view, also indicate 
that the Panel's findings regarding the use of the fishing technique of setting on dolphins in fisheries outside the ETP are consistent with the conclusions found in Exhibit MEX-161.  
7.226.  For the foregoing reasons, we conclude that, while the Panel did not expressly refer to 
Exhibit MEX-161 in the context of its assessment of the certification requirements, this, in and of 
itself, is insufficient to establish a breach of Article 11 of the DSU.
774 The excerpts from 
Exhibit MEX-161 cited by Mexico show that the conten t of this exhibit is entirely compatible with 
the Panel's findings, and do not suggest widespread tuna-dolphin association or widespread use of the fishing technique of setting on dolphins outside the ETP. 
7.227.  For all of the above reasons, we find that Mexico has not established that the Panel acted 
inconsistently with its duty to conduct an ob jective assessment of the matter, pursuant to 
Article 11 of the DSU, in its analysis of the consis tency of the certification requirements set out in 
the amended tuna measure with Article 2.1 of the TBT Agreement. 
7.2.3.4  Overall conclusions on the Pane l's analysis under Article 2.1 of the 
TBT Agreement 
7.228.  We have found that the Panel erred in its analysis of whether the amended tuna measure 
has a detrimental impact on Mexican tuna products in the US market within the meaning of 
Article 2.1 of the TBT Agreement.  
7.229.  As regards the Panel's analysis of whether the detrimental impact on Mexican tuna 
products stems exclusively from a legitimate regulatory distinction, we have not found error in the 
Panel's articulation of the legal standard. However, we have found error in the Panel's 
"reaffirm[ation]" of the supposed "finding" of the A ppellate Body that "the eligibility criteria are 
even-handed, and accordingly are not inconsiste nt with Article 2.1 of the TBT Agreement."775 We 
have further found that, in the light of the circumstances of this dispute and the nature of the 
distinctions drawn under the amended tuna measure, the Panel erred by failing to consider whether differences in the relative risks of harm to dolphins from different fishing techniques in 
different areas of the oceans explain or justify the differences in the certification requirements and 
the tracking and verification requirements app lied inside and outside the ETP large purse-seine 
fishery. In addition, we have indicated that, due to the segmented approach that it adopted in its 
analysis of the different sets of certification an d tracking and verification requirements, the Panel 
did not properly apply the legal test that it ha d identified as relevant to an assessment of 
even-handedness, namely, "whether the detrimen tal treatment can be reconciled with, or is 
rationally related to, the policy pursued by the measure at issue".
776 
7.230.  Taken together, the errors that we have identified in the two steps of the Panel's analysis 
of "treatment no less favourable" under Article 2.1 of the TBT Agreement constitute error in the application of that provision to the amended tuna measure, and deprive the Panel's ultimate 
findings thereunder of a proper legal basis. Accordingly, we reverse the Panel's discrete findings, in 
paragraph 8.2 of the Panel Report, that:  
a. the eligibility criteria in the amended tuna measure do not accord less favourable 
treatment to Mexican tuna and tuna products than that accorded to like products from 
the United States and to like products originating in any other country, and are thus 
consistent with Article 2.1 of the TBT Agreement;  
b. the different certification requirements in the amended tuna measure accord less 
favourable treatment to Mexican tuna and tuna products than that accorded to like 
                                               
772 Mexico's other appellant's submis sion, para. 145 (quoting Anderson, Cetaceans and Tuna Fisheries , 
p. 67). 
773 Mexico's other appellant's submis sion, para. 145 (quoting Anderson, Cetaceans and Tuna Fisheries , 
p. 67). 
774 Appellate Body Reports, EC – Fasteners (China) , paras. 441-442; Brazil – Retreaded Tyres , 
para. 202. 
775 Panel Report, para. 7.126. 
776 Panel Report, para. 7.91. WT/DS381/AB/RW 
 
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 products from the United States and to like products originating in any other country, in 
violation of Article 2.1 of the TBT Agreement; and  
c. the different tracking and verification requirements in the amended tuna measure accord 
less favourable treatment to Mexican tuna and tuna products than that accorded to like 
products from the United States and to like products originating in any other country, in 
violation of Article 2.1 of the TBT Agreement. 
7.2.4  Completion of the legal analysis 
7.231.  We now turn to consider whether the amended tuna measure has brought the 
United States into compliance with the DSB's recommendations and rulings in the original proceedings. We recall that completion of the legal analysis may assist in ensuring the prompt settlement and effective resolution of the dispute.  However, the Appellate Body has completed the 
legal analysis only when sufficient factual findings by the panel and undisputed facts on the record 
have allowed it to do so. 
7.232.  In order to establish that a measure is inconsistent with Article 2.1 of the TBT Agreement, 
the following elements must be established: (i) that the measure constitutes a technical regulation 
within the meaning of Annex 1.1; (ii) that the imported products are "like" the domestic products and products of other origins; and (iii) that the treatment accorded to imported products is "less 
favourable" than that accorded to like domestic products and/or like products from any other 
country.
777 Based largely on the findings in the original proceedings and the positions of the 
parties, the Panel accepted that the first two elements had been established in these compliance proceedings, and this is not appealed by the participants.
778  
7.233.  With respect to the third element, we recall that an analysis of "treatment no less 
favourable" under Article 2.1 consists of two steps: (i) whether the technical regulation at issue modifies the conditions of competition to the detriment of imported products vis-à-vis like products 
of domestic origin and/or like products originating in any other country; and, if so, (ii) whether 
such detrimental impact stems exclusively from a legitimate regulatory distinction.
779  
7.234.  Beginning with the first step, we consider whethe r the labellin g conditions under the 
amended tuna measure, taken together, modify the conditions of competition to the detriment of 
Mexican tuna products in the US market. In so doing, we must take "due cognizance"780 of the 
DSB's recommendations and rulings, including the findings of detrimental impact in the original proceedings, which constitute relevant background for our assessment. Accordingly, we begin by 
recalling the Appellate Body's finding in the original proceedings that the detrimental impact of the 
original tuna measure was "caused by the fact that most Mexican tuna products contain tuna caught by setting on dolphins in the ETP and are therefore not eligible for a 'dolphin-safe' label, 
whereas most tuna products from the United States and other countries that are sold in the 
US market contain tuna caught by other fishing methods outside the ETP and are therefore eligible for a 'dolphin-safe' label."
781 Our task is to ascertain whether the amended tuna measure has 
altered the detrimental impact that was associated with the original tuna measure, as established 
in the findings that were made by the original panel and the Appellate Body in the original proceedings and, by virtue of the DSB's adoption  of the reports from the original proceedings, 
form part of the recommendations and ru lings of the DSB in this dispute.  
                                               
777 Appellate Body Report, US – Tuna II (Mexico) , para. 229. 
778 Panel Report, para. 7.71. We note that, although the Panel referred to the like products as consisting 
of both tuna and tuna products, Mexi co had explained to the original panel that it was limiting its claims to 
tuna products, and the participants conf irmed at the oral hearing that the cl aims in this dispute, both in the 
original and Article 21.5 proceedings, are raised only with respect to tuna products. (See Original Panel Report, paras. 7.228-7.233 and 7.253-7.254) 
779 Appellate Body Reports, US – COOL , paras. 268 and 271 (referring to Appellate Body Reports,  
US – Clove Cigarettes , para. 182; and US – Tuna II (Mexico) , para. 215). 
780 Appellate Body Report, Chile – Price Band System (Article 21.5 – Argentina) , para. 136 (referring to 
Appellate Body Reports, US – Oil Country Tubular Goods Sunset Reviews (Article 21.5 – Argentina) , para. 142; 
Mexico – Corn Syrup (Article 21.5 – US) , paras. 109 and 121; US – FSC (Article 21.5 – EC II) , para. 61;  
US – Softwood Lumber IV (Article 21.5 – Canada) , paras. 68 and 77; and  US – Softwood Lumber VI 
(Article 21.5 – Canada) , para. 102). 
781 Appellate Body Report, US – Tuna II (Mexico) , para. 284. WT/DS381/AB/RW 
 
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 7.235.  As we have already explained, before the Panel and in these appellate proceedings, Mexico 
and the United States have both expressed the vi ew that the detrimental impact of the amended 
tuna measure is the same as that of the original measure. Mexico's core argument with respect to detrimental impact is that the key elements of the original measure – in particular, the 
disqualification of all tuna caught by setting on dolphins – and the relevant features of the 
US market for tuna products remain unchanged, such that most Mexican tuna products are still being excluded from access to the dolphin-safe label, whereas most like products from the 
United States and other Members are still eligible for such label.
782 Mexico also submitted that 
"virtually all of [its] purse seine tuna fleet continues to fish in the ETP by setting on dolphins".783 
The United States, for its part, does not contest the continuing applicability of the Appellate Body's conclusions on detrimental impact in the original proceedings.
784 Rather, it expressly acknowledges 
that, "because Mexico's tuna fleet is comprised 'virtually' entirely of large purse seine vessels 
setting on dolphins in the ETP, Mexico does not export 'any products to the United States that are eligible to be labelled dolphin-safe under the Amended Tuna Measure'."
785  
7.236.  As the original panel found and as both participants have acknowledged in these 
compliance proceedings, access to the dolphin-safe label constitutes an "advantage" on the US market for tuna products by virtue of that label's "significant commercial value".
786 We further 
recall that, in the original proceedings, the Appellate Body relied on the following factual findings 
by the original panel: (i) "the Mexican tuna cannery industry is vertically integrated, and the major Mexican tuna products producers and canneries own their vessels, which operate in the ETP"; 
(ii) "at least two thirds of Mexico's purse seine tuna fleet fishes in the ETP by setting on dolphins" 
and is "therefore fishing for tuna that would not be eligible to be contained in a 'dolphin-safe' tuna 
product under the US dolphin-safe labelling provis ions"; (iii) "the US fleet currently does not 
practice setting on dolphins in the ETP"; and (iv) "as the practices of the US and Mexican tuna 
fleets currently stand, most tuna caught by Mexican vessels, being caught in the ETP by setting on 
dolphins, would not be eligible for inclusion in a dolphin-safe product under the US dolphin-safe labelling provisions", while "most tuna caught by US vessels is potentially eligible for the label".
787 
These various factual elements thus supplied the foundation for the Appellate Body's finding of 
detrimental impact. At the oral hearing in these appellate proceedings, both Mexico and the United States confirmed that the relevant factual situation, as defined by these findings relied upon by the Appellate Body, has not changed. 
7.237.  We do not see that the Panel made any factual findings that go against those original 
findings. In fact, the opposite is true. In its assessment of the consistency of the amended tuna measure with Articles I:1 and III:4 of th e GATT 1994, the Panel found that the regulatory 
distinction between tuna products derived from tuna caught by setting on dolphins and tuna 
products derived from tuna caught by other fish ing methods "has the effect of denying [Mexican] 
tuna products … access to the dolphin-safe label".
788 In the light of the above, we do not see any 
Panel findings or uncontested evidence on the record indicating that the position of Mexican tuna 
products in terms of access to the dolphin-safe label has substantially changed as a result of the amended tuna measure.
789  
                                               
782 Mexico's first written submission to the Panel, paras. 223-224 and 231-232. 
783 Mexico's first written submission to the Panel, para. 227. According to Mexico, as of 2012, its tuna 
fishing fleet operating in the ETP was comprised of "39 large purse-seine vessels" and "three small vessels". (Ibid. (referring to Statement of Dr  Michel Dreyfus, Chief Researcher, Na tional Program for the Utilization of 
Tuna and Protection of Dolphins (28 March 2014) (Panel Exhibit MEX-84)) 
784 See Panel Report, para. 7.446. 
785 United States' appellant's submission, para. 329 (ref erring to and quoting Mexico's response to Panel 
question No. 57, paras. 155 and 146, respectively). We re call that, in 2009, Mexican tuna products accounted 
for only 1% of the tuna products imported into the United States. (See Original Panel Report, para. 7.355) 
786 Original Panel Report, paras. 7.289 and 7.291. See also Panel Report, para. 7.424. 
787 Appellate Body Report, US – Tuna II (Mexico) , para. 234 (quoting Original Panel Report, 
paras. 7.310, 7.314, and 7.316-7.317). 
788 Panel Report, para. 7.447. See also para. 7.498. 
789 Given that the 2013 Final Rule introduced addition al certification and tracking and verification 
requirements for tuna products containing tuna caught  outside the ETP large purse-seine fishery, it may be 
that fewer such products qualify for the label than was the case under the original measure. However, it does 
not appear that there are any Panel findings, nor any evidence on the record, uncontested or otherwise, 
regarding the extent to which the absolute levels or proportions of tuna products from the United States and 
other countries that can access the dolphin-safe label may have changed as compared to the situation under 
the original tuna measure. WT/DS381/AB/RW 
 
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 7.238.  Since the amended tuna measure maintains the overall architecture and structure of the 
original tuna measure – in particular, in terms of the regulatory distinction between tuna products derived from tuna caught by setting on dolphins and tuna products derived from tuna caught by other fishing methods – and given the participants' agreement that the relevant factual situation 
has not changed from the original proceedings, we find that, by excluding most Mexican tuna 
products from access to the dolphin-safe label, while granting conditional access to such label to 
like products from the United States and other countries, the amended tuna measure, similar to 
the original measure, modifies the conditions of competition to the detriment of Mexican tuna 
products in the US market. 
7.239.  Next, we address whether the amended tuna measure can nevertheless be said not to 
constitute less favourable treatment of Mexican tuna products by virtue of the fact that the 
detrimental impact on Mexican tuna products stems exclusively from a legitimate regulatory 
distinction. Such an examination requires scrutiny of whether the amended tuna measure is, in the light of the particular circumstances of the case, even-handed in its design, architecture, revealing 
structure, operation, and application.
790 As we have noted, where a regulatory distinction is not 
designed and applied in an even-handed manner, beca use, for example, it is designed or applied in 
a manner that constitutes a means of arbitrary or unjustifiable discrimination, that distinction 
cannot be considered legitimate for purposes of Article 2.1.791 We have also explained that, in the 
circumstances of this dispute, it is appropriate to assess whether the differences in the labelling conditions for tuna products containing tuna caught in the ETP large purse-seine fishery, on the one hand, and for tuna products containing tuna caught outside that fishery, on the other hand, 
are calibrated to the likelihood that dolphins will be adversely affected in the course of tuna fishing 
operations in the respective fisheries.
792 
7.240.  In these Article 21.5 proceedings, the Panel pointed to the statements in paragraph 292 of 
the Appellate Body report in the original proceedings regarding the basis for the finding of 
WTO-inconsistency of the original tuna measure.793 In that paragraph, the Appellate Body stated: 
From the [original panel's] findings, it thus appears that the measure at issue does 
not address adverse effects on dolphins resulting from the use of fishing methods 
predominantly employed by fishing fleets supplying the United States' and other countries' tuna producers. The [original panel] noted that the only requirement currently applicable to purse seine vessels fishing outside the ETP is to provide a 
certification by the captain that no purse seine net was intentionally deployed on or 
used to encircle dolphins during the fishing trip. This requirement, however, does not address risks from other fishing methods, such as [fish aggregating devices] FADs. As 
the [original panel] stated, risks to dolphins resulting from fishing methods other than 
setting on dolphins "could only be monitored by imposing a different substantive requirement, i.e. that no dolphins were killed or seriously injured in the sets in which 
the tuna was caught."
794 
7.241.  The Panel went on to state that adding a new substantive requirement to the amended 
tuna measure addressing the mortality or serious injury of dolphins is "precisely what the United States has done".
795 The Panel recalled that, by virtue of  the additional requirements that 
the 2013 Final Rule incorporated into the US dolphin-safe labelling regime, " all tuna, wherever and 
however caught, can only be labelled as dolphin sa fe if it was not caught in a set or other gear 
                                               
790 Appellate Body Report, US – Clove Cigarettes , para. 182. 
791 See Appellate Body Reports, US – COOL , para. 271: "[W]here a regulatory distinction is not designed 
and applied in an even-handed manner – because, for example, it is desi gned or applied in a manner that 
constitutes a means of arbitrary or unjustifiable discr imination – that distinction cannot be considered 
'legitimate', and thus the detrimental impact will reflect discrimination prohibited under Article 2.1"; and  EC – Seal Products , para. 5.306: "One of the most important factors in the assessment of arbitrary or 
unjustifiable discrimination is the question of whether the discrimination can be reconciled with, or is rationally related to, the policy objective with respect to which the measure has been provisionally justified under one of the subparagraphs of Article XX." 
792 Appellate Body Report, US – Tuna II (Mexico) , para. 286. 
793 Panel Report, para. 7.140 (quoting Appellate Body Report, US – Tuna II (Mexico) , para. 292). 
794 Appellate Body Report, US – Tuna II (Mexico) , para. 292 (quoting Original Panel Report, 
para. 7.561). (fns omitted) 
795 Panel Report, para. 7.141. WT/DS381/AB/RW 
 
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 deployment in which one or more dolphins was killed or seriously injured."796 The Panel stated that 
this meant that "the substantive certification required for all tuna … is now the same."797 In the 
Panel's view, "this new uniformity in the required substantive certification addresses the specific concern identified by the Appellate Body at pa ragraph 292 of its report, and moves the amended 
measure towards compliance with WTO law."
798 
7.242.  We agree with this reasoning by the Panel. As we have noted, the question before the 
Panel was whether the amended tuna measure, in cluding the new elements introduced by the 
2013 Final Rule, has brought the United States into compliance with the DSB's recommendations 
and rulings. The 2013 Final Rule introduced into the amended tuna measure additional 
requirements that apply outside the ETP large purs e-seine fishery, the principal of which are the 
new requirements: (i) that captains certify that no dolphins were killed or seriously injured 
irrespective of the fishing method used; and (ii) that all dolphin-safe tuna be segregated from 
non-dolphin-safe tuna from the time of the catch through the entire processing chain.799 Thus, to 
the extent that these requirements serve to enhance the capacity of the amended tuna measure to 
"address adverse effects on dolphins resulting from the use of fishing methods predominantly 
employed by fishing fleets supplying the United  States' and other countries' tuna producers"800 
outside the ETP large purse-seine fishery, they may be said to respond to the "calibration" of the 
dolphin-safe labelling regime that the Appellate Body found was lacking in the original tuna 
measure. In assessing whether the amended tuna measure is adequately calibrated to the relative adverse effects on dolphins arising outside the ETP large purse-seine fishery as compared to those inside that fishery, we must examine whether ther e are relevant factual findings by the Panel or 
undisputed evidence on the record regarding the diff erent risk profiles in these different fisheries. 
7.243.  The Panel had before it considerable evidence concerning the nature and scope of the 
relative risks associated with different fishing practices in different areas of the oceans. Mexico 
claimed before the Panel that the amended tuna measure is not even-handed because it imposes 
different and heightened requirements in the ETP large purse-seine fishery as compared to other fisheries, and that this is not justified because the adverse effects on dolphins arising from fishing 
methods other than setting on dolphins are equal to or greater than the risks associated with the 
setting on method.
801 Mexico further argued that "dolphins suffer observed and unobserved 
adverse effects – including serious injury or death – as a result of commercial tuna fishing operations throughout the fisheries of the world (i.e., both within and outside the ETP) by every 
country with a commercial tuna fishing fleet."
802 Mexico indicated before the Panel that, since the 
original proceedings, it had collected "substantial additional evidence showing that (i) tuna fishers intentionally set nets on marine mammals outside the ETP, and (ii) other methods of fishing for 
tuna are causing many thousands of dolphin mortalities."
803 Mexico submitted evidence regarding 
fishing methods and bycatch arising from various fishing methods outside the ETP, including 
                                               
796 Panel Report, para. 7.141. (emphasis original) 
797 Panel Report, para. 7.141.  
798 Panel Report, para. 7.141. 
799 As we have noted, in fisherie s other than the ETP large purse-seine fishery, the amended tuna 
measure also introduced an observer requirement in the event of a determination by the NMFS Assistant 
Administrator that observers are qual ified and authorized to certify that there are "no dolphins killed or 
seriously injured", and, in the non-ETP purse-seine fishery, "no setting on dolphins", when such observers are already on board the vessel. 
800 Appellate Body Report, US – Tuna II (Mexico) , para. 292. 
801 Mexico's first written submission to the Panel, paras. 13, 248, 263, and 306. Mexico also argued 
before the Panel, and on appeal, that there is a "zero tolerance" benchmark for risk  embodied in the amended 
tuna measure, and that this benchmark does not permit di fferences in regulation to address differences in risks 
to dolphins arising in different fish eries. We do not see that such a contention differs in substance from 
Mexico's position that, because there ar e no differences in harms to dolphins  arising in differe nt fisheries, any 
consideration of relative harms is not relevant to an analysis of the even-handedness of the distinctions drawn under the amended tuna measure. (See Panel Report, para. 7.184; Mexico's other appellant's submission, 
para. 109; and United States' appell ee's submission, paras. 80-87) 
802 Mexico's second written submission to the Panel, para. 319. (fn omitted) 
803 Mexico's first written submission to the Panel, para. 106. WT/DS381/AB/RW 
 
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 dolphin mortalities due to setting on practices, and other fishing methods such as using FADs, 
gillnets, and longline fishing.804 
7.244.  The United States responded to Mexico's claims by arguing that it was justified in drawing 
distinctions between the method of setting on dolphins and other fishing methods due to the 
different risks posed to dolphins by these different fishing methods.805 The United States did not 
contest that fishing methods other than setting on dolphins present risks to dolphins, but rather drew support from the original panel's conclusion that "certain fishing techniques seem to pose 
greater risks to dolphins than others"
806 and the Appellate Body's "conclusion" that "setting on 
dolphins is particularly harmful to dolphins."807 The United States also submitted considerable 
evidence to demonstrate that "setting on dolphins causes both observed and unobserved harms to dolphins."
808 In relation to observed harms, the United States claimed that the "number of 
dolphins killed in the ETP tuna purse-seine fishery … is the greatest known for any fishery" and 
that Mexico had failed to put forward evidence demonstrating that other fishing methods had killed as many dolphins in any fishery as had setting on dolphins.
809 Moreover, the United States 
addressed Mexico's contention that other fishing methods pose harms to dolphins that are equal to 
or greater than the harms caused by setting on dolphins, by introducing evidence of regional 
fishing management organizations, observer progra mmes, and scientists, on the levels of observed 
harms associated with fishing methods used to produce tuna products for the US market, such as 
                                               
804 Mexico listed this evidence as consisting of th e following: (i) nets are set on dolphins outside the 
ETP; (ii) it is well accepted and scientifically documented that dolphins are killed as bycatch in all of the world's major tuna fisheries; (iii) scientists  have estimated that globally, hundreds of thousands of cetaceans die from 
entanglement in fishing gear each year, including in US  fisheries; (iv) a report published by the Sea Turtle 
Restoration Project on long line fishing estimates that over 18,000 do lphins are killed a nnually by longline 
fishing in the Pacific Ocean; (v) there is substantial dolphin bycatch when using FADs in the Philippines, where 
it is estimated that 2,000 dolphins are killed annually; (vi)  gillnet fishing along the In dian coast is killing about 
10,000 cetaceans including dolphins every year which is  "alarmingly high"; (vii) when dolphins do not 
immediately drown in a gillnet (observe d adverse effects), interactions with the net causes dolphins to die later 
(unobserved adverse effects); (viii) it is now widely recognized that dolphins are severely harmed by interactions with longline fishing an d that adverse effects are both observed and unobserved; (ix) trawl fishing 
kills and injures dolphins. (Mexico's first written submission to the Panel, para. 248) In addition, Mexico submitted evidence in support of its contention before the Panel that, although the United States claimed its 
dolphin-safe labelling regime was necessary because tw o dolphin stocks in the ET P – northeastern offshore 
spotted and eastern spinner dolphins – were depleted, this was no longer the case since those dolphin stocks were growing. (Mexico's first written submission to the Panel, paras. 188-194 (referring to IDCP, 7th Meeting of the Scientific Advisory Board held on 30 October 2009, "Updated Estimates of N
min and Stock Mortality 
Limits", Document SAB-07-05 (Original Panel Exhibit MEX-91; Panel Exhibit MEX-4); AIDCP, 22nd Meeting of 
the Parties held on 30 October 2009, Minutes (Original Pa nel Exhibit MEX-117; Panel Exhibit MEX-5), item 8 on 
p. 4, and Appendix 8 on p. 10; M.N.  Maunder, "Evaluating recent trends in EPO dolphin stocks", IATTC draft 
paper (Panel Exhibit MEX-81); and V. R. Restrepo, Chair's Report of the ISSF Tuna-Dolphin Workshop held 
on 25-26 October 2012 (Panel Exhibit MEX-82), p. 3)) 
805 United States' second written su bmission to the Panel, para. 92. 
806 United States' first written submission to the Panel, para. 71 (quoting Original Panel Report,  
para. 7.438; and referring to Appellate Body Report, US – Tuna II (Mexico) , para. 288). 
807 United States' first written submission to the Panel, para. 71 (quoting Appellate Body Report,  
US – Tuna II (Mexico) , para. 289). 
808 United States' first written submission to the Pane l, para. 89 (referring to Original Panel Report,  
paras. 7.493, 7.504, and 7.738;  and Appellate Body Report, US – Tuna II (Mexico) , para. 251). 
809 United States' second written submission to the Panel, para. 16 (referring to T. Gerrodette, "The 
Tuna-Dolphin Issue", in Encyclopedia of Marine Mammals , 2nd edn, W.F. Perrin, B.  Würsig, J.G.M. Thewissen 
(eds.) (Oxford, 2009), p. 1192 (Panel Exhibit US-29)). WT/DS381/AB/RW 
 
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 non-setting on purse-seine fishing, longline fishing, and pole-and-line fishing.810 In regards to 
unobserved harms, the United States submitted that other fisheries are not "producing the same level of unobserved harms, such as cow-calf separation, muscular damage, immune and reproductive system failures, which 'arise as a result of the chase in itself,' as the purse seine 
fishery in the ETP."
811 In support of this position, the United States offered IATTC data on the 
numbers of dolphins chased and captured in th e years 2009-2013 showing that "the scale of the 
unobserved harms caused by the chase in the ETP is unprecedented."812 
7.245.  We recall that, at the outset of its assessment of the relative harms posed by setting on 
dolphins versus other fishing methods, the Panel focused mainly on the unobserved harms associated with different fishing methods.
813 Observing that the Appellate Body found that setting 
on dolphins causes both observed and unobserved harm to dolphins, the Panel nevertheless 
considered that "what makes setting on dolphins particularly harmful is the fact that it causes 
certain unobserved effects  beyond  mortality and injury 'as a result of the chase itself'."814 
Subsequently, the Panel acknowledged that "[t]he evidence presented by Mexico, especially in its 
first written submission, certainly suggests that very significant numbers of dolphins are killed in 
tuna fishing operations outside of the ETP large purse seine fishery."815 The Panel therefore 
accepted that tuna fisheries other than the ETP large purse-seine fishery may, and in fact have, 
caused harms to dolphins.  
7.246.  The Panel, however, did not address what the evidence adduced by the parties indicated in 
respect of the overall relative  harms, both observed and unobserved, associated with setting on 
dolphins versus other fishing practices, but rather focused only on whether that evidence 
undermined its understanding that these fishing practices are distinguishable on the basis of 
unobserved harms. Thus, in respect of gillnet fish ing, the Panel referenced Mexico's substantial 
                                               
810 The United States indicated that the evidence it had put forward demonstrates the following: (i) in 
the ETP, dolphin sets account for virtually all observed dolphin mortalities and serious injuries despite the fact 
that dolphin sets constitute less than half the total number of sets on average; (ii) the percentage of dolphins killed in the ETP purse-seine fishery from dolphin sets has never fallen below 99% of total observed dolphin 
mortalities in the years 2009-2013; (iii) in the Western Central Pacific Ocean purse-seine fishery, dolphin mortality per 1,000 sets was an estimated 26.98 dolphi ns in 2007-2009 and 2.64 dolphins in 2010, whereas, in 
the ETP purse-seine fishery, dolphin mortality per 1,000 sets was 56.1 dolphins in 2009 and 53.4 dolphins in 2010; (iv) the average numbers of dolphins killed each ye ar in the Atlantic and Hawaii US longline fisheries 
between 2006 and 2010 are mere fractions of the number killed each year in the ETP and of the number allowed to be killed under the AIDCP; (v) in the Hawaii longline fishery, the estima ted average annual dolphin 
mortality from 2006-2010 was 40.4 animals per year; (vi) pole and line fishing is not associated with dolphin bycatch or bycatch of any marine mammal; and (vii) pu rse-seine fishing other than  by setting on dolphins, 
longline fishing, and pole and line fishing are often employed without any dolphin within sight of the vessel and without any dolphin interaction at all, whereas all dolphin sets are inherently  dangerous to dolphins. 
(United States' second written submission to the Panel, para. 23 (emphasis omitted)) 
811 United States' first written submission to the Panel, para. 113 (quoting Original Panel Report, 
paras. 7.499 and 7.504; and referring to the review of A.C. Myrick, Jr. and P.C. Perkins, "Adrenocortical color darkness and correlates as indicato rs of continuous acute premortem stress in chased and purse-seine 
captured male dolphins" (1995) 2 Pathophysiology  (Original Panel Exhibit US -11; Panel Exhibit US-48), 
p. 191). 
812 United States' response to Pane l question No. 15, para. 82. The Un ited States added that "IATTC 
data indicates that in the years 2009-2013 large ETP purse seine vessels chased 31.3 million  dolphins, 
capturing 18.5 million  of them." (Ibid. (referring to Tables Su mmarizing Fishery-by-Fishery Evidence on the 
Record (Panel Exhibit US-127), Table 1, "Association of  Dolphins and Tuna in Various Fisheries") (emphases 
original)) See also United States' first written submissi on to the Panel, para. 73 (referring to IATTC, Eastern 
Pacific Ocean (EPO) Dataset 2009-2013 (9 May 2014) (Panel Exhibit US-26 (corrected)); United States' response to original panel question No. 31, para. 70; and IDCP, 34th Meeting of the International Review Panel held on 9-10 October 2003, "Effectiveness of Technical Gu idelines to Prevent High Mortality During Sets on 
Large Dolphin Herds", Document IRP-34-10 (revised) (Panel Exhibit US-27), Table 2 at p. 4). The United States also challenged Mexico's position that the United States itself considered that ETP dolphin stocks were recovering, and offered its own sc ientific evidence to show that dolphin populations are not increasing. 
(See United States' first written submission to the Panel, paras. 104-108 (referring to, inter alia , A.E. Punt, 
Independent Review of the Eastern Pacific Ocean Dolphin Population Assessment , IATTC Special Report 21 
(2013) (Panel Exhibit US-49), pp. 5-6; and S.B. Reilly et al., Report of the Scientific  Research Program Under 
the International Dolphin Conservation Program Act , NOAA Technical Memorandum NMFS (March 2005) (Panel 
Exhibit US-28), pp. 31-32)) 
813 Panel Report, paras. 7.120-7.121 (referring to Appellate Body Report, US – Tuna II (Mexico) , 
para. 289; and quoting, without attributio n, Original Panel Report, para. 7.499). 
814 Panel Report, para. 7.122 (quoting Original Panel Report, para. 7.504). 
815 Panel Report, para. 7.129 (referring to Mexico's first written submission to the Panel, section III.A). WT/DS381/AB/RW 
 
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 evidence showing that gillnets kill and seriously injure dolphins, but stated that none of this 
evidence indicated that gillnets have the same kind of unobserved effects as has setting on dolphins.
816 Similarly, in respect of longline fishing, the Panel stated that, although Mexico's 
evidence indicated that longlining is having a negative effect on the sustainability of dolphin 
populations, none of that evidence suggests that  longline fishing has unobserved effects similar to 
those caused by setting on dolphins.817 Furthermore, the Panel explicitly acknowledged that Mexico 
submitted evidence concerning the extent of mortality and serious injury caused by tuna fishing 
methods including FAD fishing, longline fishing, gillnet fishing, trawl fishing, and driftnet fishing, 
but again opined that none of this evidence sugg ested that such fishing methods inflict the same 
kinds of unobserved effects as setting on dolphins.818 The Panel therefore concluded that Mexico 
had not demonstrated that fishing methods other than setting on dolphins "consistently cause" 
harms similar to the harms to dolphins caused by setting on dolphins.819 
7.247.  We note that the Panel's conclusion could be read to imply that it found that Mexico had 
not demonstrated that fishing methods other than setting on dolphins consistently cause observed 
and unobserved harms to dolphins similar to the observed harms caused by setting on dolphins, 
and that Mexico had also failed to demonstrate that such other fishing methods cause unobserved harms to dolphins similar to those caused by setting on dolphins. In fact, however, when read 
together with the reasoning that preceded it, it is clear that the Panel's conclusion rests solely on 
its finding that the unobserved  harms differed between setting on and other fishing methods. This 
is because, whenever the Panel referred to the ev idence of observed mortality or serious injury 
arising from fishing methods other than setting on dolphins, it was only to establish that such 
harms occur, but without indicating how the nature or extent of those harms compare to  the 
observed harms arising from setting on dolphins. Indeed, although the Panel referred to observed 
mortality or serious injury arising from fishing methods other than setting on dolphins, we do not 
see that the Panel ever compared those harms with those arising from setting on dolphins in a 
manner that allowed for a comparative assessment of the extent  of those harms in relation to  each 
other.  
7.248.  The limited scope of the Panel's conclusion is relevant in two respects. First, the 
disagreement between the parties regarding whet her the amended tuna measure is even-handed 
rested on fundamentally different premises concer ning the risks associated with different fishing 
practices. Mexico maintained that the observed mortality or serious injury from practices other 
than setting on dolphins was "equal to or greater than"
820 that associated with setting on dolphins, 
whereas the United States asserted that the risks associated with practices other than setting on dolphins produced "nowhere near the observed dolp hin mortality or serious injury that setting on 
dolphins does".
821 The parties also disagreed regarding the nature and extent of unobserved 
harms. The United States contended that tuna-dolphin association and related unobserved harms are unique to the ETP large purse-seine fishery
822, whereas Mexico maintained that such 
association also occurs outside the ETP, and that unobserved harms also result from fishing 
methods other than setting on dolphins.823 By failing to consider the relative risks posed by 
different fishing methods in respect of observed  mortality or serious injury, while focusing solely 
on the narrower difference in the respective risks attributable to unobserved  harms, the Panel 
never resolved the question of the overall levels of risk in the different fisheries, and how they 
compared to each other, notwithstanding that bo th parties had addressed such comparative risk 
profiles in their pleadings in support of their arguments regarding even-handedness. We note, in 
this regard, that, at the oral hearing in this appeal, both Mexico and the United States criticized 
the Panel for focusing on too narrow a range of harms and, in particular, for not dealing with observed harms. 
                                               
816 Panel Report, para. 7.130. 
817 Panel Report, para. 7.131. 
818 Panel Report, para. 7.132. (fns omitted) 
819 Panel Report, para. 7.135: "[O]ur view is that Mexico has not provided evidence sufficient to 
demonstrate that setting on dolphins does not cause observed and unobserved harms to dolphins, or that 
other tuna fishing methods consistently cause similar harms." 
820 Mexico's first written submission to the Panel, paras. 13, 248, 263, and 306. 
821 United States' second written submission to the Panel, para. 201. See also United States' first written 
submission to the Panel, para. 236. 
822 United States' first written submission to the Panel, paras. 85 and 338-339. 
823 Mexico's first written submission to the Panel, para. 248. WT/DS381/AB/RW 
 
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 7.249.  Second, arriving at a conclusion in respect of the relative  risks attributable to different 
fisheries, including in respect of both observed and unobserved harms, was, in our view, 
particularly important given that the very issue the Panel was seeking to address was whether the new requirements of the amended tuna measure, which apply exclusively to fisheries other than 
the ETP large purse-seine fishery, adequately addre ss the risks of harm to dolphins arising in such 
fisheries.
824 Moreover, the two principal additional requirements – namely, that a captain must 
certify that there were no dolphins killed or seriously injured, and that tuna caught must be 
segregated into dolphin-safe and non-dolphin-safe storage areas – both seek to enhance the 
manner in which the measure addresses the risks of observed mortality or serious injury outside of the ETP large purse-seine fishery. Yet, the Panel never sought to compare the relative  harms in 
respect of observed  mortality or serious injury. Instead, the Panel reached a conclusion only on 
the basis of a comparative assessment of unobserved  harms. On the basis of the foregoing 
concerns, we do not consider that the Panel put itself in a position to conduct an assessment of whether the amended tuna measure is even-handed in addressing the respective risks of setting 
on dolphins in the ETP large purse-seine fishery versus other fishing methods outside that fishery. 
7.250.  We recall that, in the original proceedings, the question concerning the relative risks to 
dolphins arising in different fisheries was framed by the original panel's findings that adverse 
effects consisting of observed mortality or serious injury arise in fisheries outside the ETP, but that 
the original tuna measure did not require any certification in respect of tuna caught in those fisheries that no dolphins were killed or seriousl y injured. On that basis, the Appellate Body was 
able to conclude that, while the original tuna measure fully addressed the adverse effects on 
dolphins resulting from setting on dolphins in the ETP, it did "not address mortality (observed or 
unobserved) arising from fishing methods other than setting on dolphins outside the ETP".
825 In 
these circumstances, it was reasonable to consid er that, irrespective of any differences in the 
relative risks, the original tuna measure did not address the incidence of harms arising from 
practices other than setting on dolphins because there was no certification required to document whether any dolphins had been killed or seriously injured. For that reason, the Appellate Body was 
able to state that, " even accepting  that the fishing technique of setting on dolphins is particularly 
harmful to dolphins", it was not persuaded that the measure was even-handed, as argued by the United States.
826 
7.251.  In these Article 21.5 proceedings, however, the question as to the relative risk profiles 
associated with different fishing practices in different areas of the oceans has become more acute. 
Given that the amended tuna measure introduced a requirement outside the ETP large purse-seine fishery that captains certify that no dolphins were killed or seriously injured, and that, for that 
purpose, segregation of dolphin-safe and non-dolphin-safe tuna must be maintained, the exercise 
of gauging whether these new requirements are sufficient to address the risks posed to dolphins outside the ETP large purse-seine fishery requires a more thorough understanding of the relative 
risk profile outside that fishery as compared to th e risks to dolphins within that fishery, and, in 
particular, the risks associated with setting on dolphins.
827 M o r e o v e r ,  a s  w e  h a v e  n o t e d ,  t h e  
parties presented conflicting accounts, supported by considerable arguments and evidence, as to why the relative risks of observed mortality or serious injury did or did not justify the differences 
in regulatory treatment inside and outside the ETP large purse-seine fishery provided for under the 
amended tuna measure. 
                                               
824 As we noted, the Panel appears to have sought to address this question because of the significance it 
attached to the Appellate Body's conclusion in the orig inal proceedings that "risks to dolphins resulting from 
fishing methods other than setting on dolphins 'could only be monitored by imposing a different substantive 
requirement, i.e. that no dolphins were  killed or seriously injured in the se ts in which tuna was caught'." (Panel 
Report, para. 7.140 (quoting Appellate Body Report, US – Tuna II (Mexico) , para. 292, in turn quoting Original 
Panel Report, para. 7.561)) 
825 Appellate Body Report, US – Tuna II (Mexico) , para. 297 (quoting Original Panel Report, 
para. 7.544). 
826 Appellate Body Report, US – Tuna II (Mexico) , para. 297. (emphasis added) 
827 On appeal, Mexico argues for the use of an "obj ective, scientifically-established" benchmark – such 
as potential biological removal (PBR) levels – that co uld be used to compare how different fishing methods 
each affect the sustainability of dolphin populations. (Mexico's other appellant's submission, para. 110) For its part, the United States points to th e insufficiency of PBR data across fi sheries and rejects the relevance of 
PBR levels for examining relative risk profiles. (United States' appellee's submission, paras. 88-90) We do not 
exclude that reference to such obje ctive indicators might assist in an  assessment of whether regulatory 
differences in the treatment of diffe rent fisheries can be explained on the basis that such treatment is 
calibrated to, or commensurate with, the relative risks to dolphins arising from di fferent fishing methods in 
different areas of the oceans. WT/DS381/AB/RW 
 
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 7.252.  We do not discount the difficulty associated with making such an assessment of the 
respective risks, particularly in the light of  the highly contested evidence adduced by the 
parties.828 Neither do we consider that the Panel was necessarily in a position to come to a 
definitive or precise view as to the extent to which the relevant risk profiles differed. However, for 
the reasons set out above, we do not see that the Panel in these proceedings set out to examine 
the extent of mortality or serious injury arising from fishing methods in different areas of the oceans so as to enable itself to gauge properly the overall relative risks or levels of harm to 
dolphins arising in those fisheries, which was needed in order to assess whether the differences in 
the dolphin-safe labelling conditions under the amended tuna measure are appropriately tailored to, and commensurate with, those respective risks.  
7.253.  For instance, we note the Panel's finding th at captains, in comparison to observers, do not 
necessarily and always have the technical skills requir ed to certify that no dolphins were killed or 
seriously injured.
829 As the Panel found, this difference, as between captains and independent 
observers, in the respective training and technical skills required to certify the dolphin-safe status 
of tuna "may result in inaccurate information being passed to consumers, in contradiction with the 
objectives of the amended tuna measure".830 We also note the Panel's conclusions that the 
tracking and verification requirements that apply outside the ETP large purse-seine fishery are less 
burdensome than those that apply inside that fish ery in terms of their depth, accuracy, and degree 
of government oversight831 and that this "may contribute to inaccurate labelling of tuna caught 
outside the ETP large purse seine fishery".832 In the absence of a proper assessment by the Panel 
of the relative risks existing inside and outside the ETP large purse-seine fishery, the Panel limited 
its ability to determine whether the discriminatory aspects of the amended tuna measure can be 
explained as being properly tailored to, or commens urate with, the differences in such risks in the 
light of the objective of protecting dolphins from adverse effects arising in different fisheries. For 
similar reasons, the Panel's limited analysis in respect of the relative risk profiles in turn constrains 
our ability to complete the legal analysis in this regard. 
7.254.  There are, however, other features of the amended tuna measure that are not dependent 
on an assessment of the relative risks associated with different fishing methods in different areas 
of the oceans. In particular, we have previously examined the Panel's analysis regarding the determination provisions set out in the amended tuna measure, and in particular the provisions that trigger a requirement to provide certification by observers for specific fisheries in scenarios in 
which the risks of harm to dolphins in such fisheries would be comparably high to those existing in 
the ETP large purse-seine fishery. We recall, in this context, the Panel's finding that the determination provisions are "an integral pa rt" of the "certification system" under the 
US dolphin-safe labelling regime.
833 In general, for tuna caught in fisheries other than the 
ETP large purse-seine fishery, the required certificat ion(s) need be provided only by a captain. Yet, 
as we previously explained, depending on the category of fishery concerned, and on whether 
certain determinations have been made by the NMFS Assistant Administrator, then, in addition to 
the required captain certification(s), the amended tuna measure in some circumstances also conditions access to the dolphin-safe label on the provision of a certification by a qualified and approved observer in respect of the conditions, where applicable, of "no setting on dolphins" and 
"no dolphins killed or seriously injured". In particular, such observer certification is required if a 
determination has been made by the NMFS Assistant Administrator: (i) within the non-ETP purse-seine fishery, that there is a regular and significant tuna-dolphin association, similar to the 
                                               
828 Panel Report, para. 7.46. The Panel stated that "t he relevant factual eviden ce is highly contested 
and, with respect to some of the issues in dispute, minimal", and that, "[i]n particular, there appears to be limited scientific evidence concerning the scope and nature of dolphin mortalities in some non-ETP fisheries". (Ibid.) 
829 Panel Report, para. 7.233. 
830 Panel Report, para. 7.233. 
831 Panel Report, paras. 7.354 and 7.370. 
832 Panel Report, para. 7.382. 
833 Panel Report, para. 7.257. WT/DS381/AB/RW 
 
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 tuna-dolphin association in the ETP; or (ii) within "all other fisheries"834, that there is a regular and 
significant mortality or serious injury of dolphins.835  
7.255.  In addressing the Panel's analysis of the certification requirements under the second stage 
of the "treatment no less favourable" analysis under Article 2.1 of the TBT Agreement, we did not 
accept the United States' claims that the Panel erred in its analysis of the determination provisions 
set out in Sections 1385(d)(1)(B)(i) and (d)(1)(D) of the DPCIA and Sections 216.91(a)(2)(i) and (a)(4)(iii) of the implementing regulations. Specifically, we found that Mexico has properly 
identified the determination provisions as part of its broader claim under Article 2.1 of the 
TBT Agreement, and that the United States has not established that the Panel erred, either in its 
application of Article 2.1 or under Article 11 of the DSU, in analysing the determination provisions by focusing on the design, structure, an d expected operation of the measure.  
7.256.  We note that, in their design
836, the determination provisions seem to apply to all fisheries 
other than the ETP large purse-seine fishery where the risk of harm to dolphins approximates that existing in the ETP large purse-seine fishery. Indeed, this link is explicit on the face of the 
determination provision applicable to the non-ETP purse-seine fishery in that it concerns a finding 
that regular and significant association occurs "similar to the association between dolphins and tuna in the [ETP]".
837 As the Panel explained, the determination provisions "appear to be designed 
to enable the United States to impose conditions  on fisheries other than the ETP large purse seine 
fishery where the conditions in the former approach those of the latter".838 As the Panel remarked, 
this helps to ensure that similar situations are treated similarly under the amended tuna measure. Thus, in the non-ETP purse-seine fishery, the existing requirement that a captain provide a 
certification in respect of the conditions of "no setting on dolphins" and "no dolphins killed or 
seriously injured" is supplemented by an additional requirement of observer certification in respect of those two conditions when a determination is made that there is regular and significant 
tuna-dolphin association, similar to the tuna-dolphin association in the ETP. When such a 
determination of tuna-dolphin association in the non-ETP purse-seine fishery is made, the certification requirements are thereby heightened in terms of who i s  t o  m a k e  t h e  r e q u i r e d  
certifications (captain and observer). Moreover, the amended tuna measure explicitly states that 
such a determination is to be made when the association is similar to the association between dolphins and tuna in the ETP.
839 Because the Panel found that observers are more qualified, and 
therefore more likely to make accurate certifications in respect of mortality or serious injury, this 
determination appears, in our view, to enhance the correlation, for fisheries other than the 
ETP large purse-seine fishery, between the risks of harm to dolphins and the manner in which the measure seeks to address those risks.  
7.257.  The same can be said of the determination provision applicable to "all other fisheries", 
which supplements the existing requirement that a captain provide a certification in respect of the 
                                               
834 We recall that the category of "all other fisheries"  includes non-purse-seine vessels in any fishery and 
small purse-seine vessels in the ETP. 
835 We further noted that the amended tuna measure al so provides, in fisheries other than the ETP large 
purse-seine fishery, for an  observer certification where observers are determined by the NMFS Assistant 
Administrator to be qualified and authorized to certify th at there are "no dolphins killed or seriously injured", 
and, for non-ETP purse-seine vessels, "no setting on dolphins", and such observers are already on board the 
vessel for other reasons. 
836 The United States confirmed, in response to questioning at the oral hearing that, to date, the NMFS 
Assistant Administrator has not made  a determination that any fishery outside the ETP large purse-seine 
fishery has either regular and significant tuna-dolphin a ssociation or regular and significant mortality or serious 
injury of dolphins. (See also Panel Report, para. 3.22) We  also note that, in responding to public comments on 
the proposed 2013 Final Rule, the NMFS identified the following question that it had received: "Is there a defined process for determining 'regul ar and significant,' and has the Depa rtment of Commer ce defined it?" 
The NMFS responded that the 2013 Final Rule was not intended to address or revise the "regular and significant" standard already in the DPCIA and the impl ementing regulations and that the NMFS had not made 
any determination because it had "no credible reports of  any fishery in the world, other than the tuna purse 
seine fishery in the ETP, where dolphins are systematic ally and routinely chased and encircled each year in 
significant numbers by tuna fishing ve ssels, or any tuna fishery that has regular and significant mortality or 
serious injury of dolphins". (2013 Final Rule, Comment 11, p. 41000) 
837 Section 1385(d)(1)(B)(i) of the DPCIA; Section 216. 91(a)(2)(i) of the implementing regulations. 
838 Panel Report, para. 7.263. The panelist who wrote a separate opinion also cited the determination 
provisions as an example of where the amended tuna measure "enable[s] the United States to impose the 
same requirements in fisheries where the same degree of risk prevails". (Ibid., para. 7.280) 
839 Section 1385(d)(1)(B)(i) of the DPCIA; Section 216. 91(a)(2)(i) of the implementing regulations. WT/DS381/AB/RW 
 
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 condition of "no dolphins killed or seriously injured" with a requirement for the same certification 
from an observer when there is a determination made that there is regular and significant mortality or serious injury in that fishery. When such a determination is made, the certification requirements are thereby heightened in terms of who is to make the required certifications 
(captain and observer). Although the amended tuna measure does not state what criteria inform a 
determination of regular and significant mortality or serious injury, we would understand the reference to "regular" and "significant" mortality or serious injury as indicating that there exist 
risks of dolphin death or serious injury that are equivalent to or greater than those existing in the 
ETP large purse-seine fishery. We therefore consider that this determination also appears to enhance the correlation, in respect of "all other fi sheries", between the risks of harm to dolphins 
and the manner in which the measure seeks to address those risks.  
7.258.  Like the Panel, however, we observe that  the determination provisions do not appear to 
address other scenarios in which there may be heig htened risks of harm to dolphins associated 
with particular fishing methods in fisheries other than the ETP large purse-seine fishery.
840 As 
noted, the determination provision applicable to the non-ETP purse-seine fishery allows for the 
addition of a requirement for observer certification if there is a determination of "regular and significant association", but not for a determination of "regular and significant mortality or serious 
injury".
841 In our view, this is difficult to reconcile with the fact that such an observer certification 
is required in the ETP large purse-seine fishery, and that such a determination, on the basis of "regular and significant mortality or serious injury", can be made pursuant to the other relevant determination provision, which is applicable to "all other fisheries".
842 We recall, in this regard, the 
Panel's finding that captains, in comparison to observers, do not necessarily and always have the 
technical skills required to certify that no dolphins were killed or seriously injured.843 
7.259.  According to the Panel, when asked why specific fisheries within the non-ETP purse-seine 
fishery cannot be subject to a determination that they are causing "regular  and significant dolphin 
mortality or serious injury", the United States provided no explanation.844 On appeal, the 
United States explains that a focus on mortality would not take into account the unobserved harms 
to dolphins resulting from setting on dolphins.845 The United States also maintains that, due to the 
direct positive correlation between tuna-dolphin association and observed mortality and serious injury in purse-seine fisheries, there is no eviden ce on the record that a purse-seine fishery exists 
where there is regular and significant mortality without tuna-dolphin association also being 
present.
846 We do not find these arguments convincing. First, while we agree that a focus only on 
mortality might not take into account the unobserved  harms to dolphins resulting from setting on 
dolphins, the question here is rather whether the determination provisions should also address a 
situation of regular and significant mortality or serious injury in addition to  addressing a situation 
of regular and significant tuna-dolphin association. Any concerns in respect of unobserved harms arising from setting on dolphins would be addressed by the existing determination provision to the 
extent that it requires observer certification if there is a determination of "regular and significant 
association". Instead, we are expressing concern that the determination provision does not allow for comparable regulation of a risk scenario where there is regular and significant mortality or serious injury in respect of non-setting on practices by purse-seine vessels inside versus outside 
the ETP.  
7.260.  Second, we do not find persuasive the United States' argument that there is no basis for 
imposing an observer requirement in the absence of evidence that a purse-seine fishery exists 
where there is regular and significant mortality without tuna-dolphin association also being 
present. We are not convinced that, in the abse nce of tuna-dolphin association, there is no 
possibility of regular and significant mortality or serious injury occurring in a fishery. As the 
Appellate Body noted in the original proceedings, requiring certification that purse-seine vessels 
have not engaged in setting on dolphins does not address the risks involved in such vessels' use of 
                                               
840 Panel Report, para. 7.263. As the Panel explained, by virtue of the determination provisions, 
"fisheries other than the ETP large purse seine fishery may be treated differently, and less stringently, under 
the amended tuna measure even where the conditions in that fishery mirror those in the ETP large purse seine fishery, either in terms of the leve l of dolphin mortality or the degree of tuna-dolphin association." (Ibid.) 
841 Section 1385(d)(1)(B)(i) of the DPCIA; Section 216. 91(a)(2)(i) of the implementing regulations. 
842 Section 1385(d)(1)(D) of the DPCIA; Section 216.91(a)(4)(iii) of the implementing regulations. 
843 Panel Report, para. 7.233. 
844 Panel Report, para. 7.260. 
845 United States' appellant's submission, para. 242. 
846 United States' appellant's submission, paras. 243-245. WT/DS381/AB/RW 
 
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 other fishing methods, such as using FADs.847 Moreover, the amended tuna measure contemplates 
the existence of risks of mortality or serious injury  in the absence of setting on dolphins given that 
the determination provision linked to regular and significant mortality or serious injury applies in "all other fisheries" existing both inside and outside the ETP. For the foregoing reasons, we see no 
convincing explanation as to why such a scenario should be excluded from the dolphin-safe 
labelling regime, thereby preventing the possibility of triggering the addition of an observer requirement for non-setting on activities in the non-ETP purse-seine fishery, when such a 
requirement already exists for non-setting on activities in the ETP large purse-seine fishery and, 
upon a determination, in "all other fisheries".  
7.261.  We also consider that our observations ab out the determination provisions are particularly 
relevant in the light of statements made by the Appellate Body regarding the shortcomings of the 
original tuna measure. The Appellate Body stated that it did not understand the original panel to 
have suggested that imposing a requirement that an independent observer certify that no dolphins were killed or seriously injured would be the only way for the United States to calibrate its 
dolphin-safe labelling provisions to the risks that the original panel found were posed by fishing 
techniques other than setting on dolphins. The Appellate Body added, however, that "such a 
requirement may be appropriate in circumstances in which dolphins face higher risks of mortality 
or serious injury".
848 Thus, even if the United States may reasonably have sought to implement 
the DSB's recommendations and rulings by implementing a condition of "no dolphins killed or seriously injured" other than through an observer certification, the Appellate Body also suggested that an observer requirement may be appropriate when dolphins face higher risks of mortality or 
serious injury.  
7.262.  In respect of the determination provision applicable to "all other fisheries", there is also a 
question as to whether this provision sufficiently addresses scenarios in which there may be 
elevated risks of harm associated with particular fishing methods outside the ETP large purse-seine 
fishery. We recall that, for this category of fisheries, the determination provision allows for the addition of a requirement of observer certification if there is a determination of "regular and 
significant mortality or serious injury", but does not provide for a determination of "regular and 
significant association".
849  
7.263.  Both before the Panel, and again on appeal, the United States argues that there is no need 
to provide for the possibility to make a determination linked to tuna-dolphin association in these 
fisheries since such determination would have no impact on the degree of mortality or serious 
injury caused by fishing methods other than setting on dolphins.850 As the United States explains, 
if there is a correlation between tuna-dolphin association and the risk of mortality or serious 
injury, then the higher risks to dolphins would already be addressed by a determination regarding 
regular and significant mortality or serious injury.851 The United States also questions the risks 
posed by such a correlation by noting that the tuna-dolphin association is only dangerous to 
dolphins when a purse-seine vessel intentionally interacts with dolphins and seeks to take 
advantage of that association by encircling them with purse-seine nets.852  
7.264.  We see some merit in the United States' contention that the more relevant consideration in 
respect of a tuna-dolphin association is whether there is a vessel that is capable of intentionally 
targeting and taking advantage of that association, and which would thereby produce the observed 
and unobserved harms to dolphins that are linked to the fishing method of setting on dolphins. Like the United States, we recognize that the other fisheries to which this determination provision 
applies do not concern the operation of large purse-seine vessels, which are the only vessels that 
are recognized as capable of setting on dolphins. At the same time, we also take note of the Panel's view that, wherever dolphins associate with tuna, "they are more likely to interact with 
                                               
847 Appellate Body Report, US – Tuna II (Mexico) , para. 292. 
848 Appellate Body Report, US – Tuna II (Mexico) , fn 612 to para. 296. 
849 Section 1385(d)(1)(D) of the DPCIA; Section 216.91(a)(4)(iii) of the implementing regulations. 
850 Panel Report, para. 7.261. 
851 United States' appellant's submission, para. 247. Th e United States also argues that, in any event, 
the evidence on the record contradicts the Panel's "c ommon-sense" approach because it shows that, in the 
ETP, where it is uncontested that tuna-dolphin associat ion exists, observed harms are very low for vessels that 
do not set on dolphins. (Ibid., paras. 248-249) 
852 United States' appellant's submission, para. 253. WT/DS381/AB/RW 
 
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 tuna fishing gear, even if such interaction is accidental or unintentional".853 For this reason, the 
Panel considered that, even for fishing methods that do not deliberately target the association of dolphins with tuna, "the risk of mortality or serious injury is necessarily heightened"
854 where 
there is association and that, accordingly, "observers may be necessary whenever there is a 
'regular and significant' tuna-dolphin association, regardless of whether the association occurs in a 
purse seine fishery or any other type of fishery".855 I t  i s  a l s o  n o t  c l e a r  t o  u s  w h e t h e r  t h e  
association of dolphins and tuna necessarily heightens the risk to dolphins from non-purse-seine 
fishing methods, nor whether any such heighten ed risk could be adequately addressed by a 
determination that there is "regular and significant mortality or serious injury". To the extent that there may in fact be a heightened risk to dolphins due to association, comparable to that existing in the ETP large purse-seine fishery, even where the fishing methods employed are not capable of 
setting on dolphins, and that such risk would not be addressed by a determination of "regular or 
significant mortality or serious injury", we would consider this to be relevant to an assessment of the even-handedness of the amended tuna measure. 
7.265.  Finally, we note that our analysis regarding the determination provisions is premised on 
the existence of risks outside the ETP large purse- seine fishery that are comparably high to the 
risks existing in the ETP large purse-seine fishery.
856 As the Panel explained, the determination 
provisions "appear to be designed to enable the United States to impose conditions on fisheries 
other than the ETP large purse seine fishery where the conditions in the former approach those of the latter".
857 We recall from our discussion of the measure at issue that there are differences 
between the documentation requirements that the amended tuna measure applies inside and 
outside the ETP large purse-seine fishery in respect of segregation.858 We also recall that the Panel 
found that the differences in the tracking and verification requirements are such that there are differences in the depth, accuracy, and degree of government oversight that is legally required 
under the amended tuna measure with respect to tuna products derived from tuna caught in the 
ETP large purse-seine fishery, on the one hand, and from tuna caught in all fisheries other than the ETP large purse-seine fishery, on the other hand.
859 In such circumstances, we would expect 
that any determination outside the ETP large purse-seine fishery would entail not only the 
heightened certification requirements, but also tracking and verification requirements that work together with and reinforce certification in addressing this heightened risk. 
7.266.  In conclusion, in the absence of a proper assessment by the Panel of the respective risks 
posed to dolphins inside and outside the ETP large purse-seine fishery, we are unable to complete 
the legal analysis and assess fully whether all of the regulatory distinctions drawn under the amended tuna measure can be explained and justified in the light of differences in the relative 
risks associated with different methods of fishing for tuna in different areas of the oceans. 
                                               
853 Panel Report, para. 7.261. According to the Panel, "the more dolphins there are in the vicinity, the 
more likely [it is] that one or more dolphins will be killed or seriously injured." (Ibid.) 
854 Panel Report, para. 7.261. 
855 Panel Report, para. 7.262. 
856 We note that the determination provisions may also aim at addressing situations where the risks to 
dolphins are comparably high to thos e associated with the other fishing me thod that is disqualified from access 
to the dolphin-safe label, namely, large-scale driftnet fishing in the high seas. 
857 Panel Report, para. 7.263. The panelist who wrote a separate opinion also cited the determination 
provisions as an example of where the amended tuna measure "enable[s] the United States to impose the 
same requirements in fisheries where the same degree of risk prevails". (Ibid., para. 7.280) 
858 We have noted in our discussion  of the measure at issue that th e regime for segregation of tuna 
caught in the ETP large purse-seine fishery is supported  by documentary requirements  consisting of separate 
TTFs, one of which is used to record information regard ing each dolphin-safe tuna set, and another to record 
the same information in respect of non-dolphin-safe sets. All tuna caught by US-flagged large purse-seine 
vessels fishing in the ETP must be accompanied by th ese TTFs, and importers of tuna and tuna products 
containing tuna caught by non-US-flagged ETP large pu rse-seine vessels must provide the TTF numbers when 
submitting the required documents for importation.  Moreover, the TTFs or TTF numbers accompany the 
relevant tuna from the time of catch throughout the fishing and production proces s. We have further noted 
that all fisheries outside the ETP large purse-seine fishery are required to segregate dolphin-safe and non-dolphin-safe tuna from the time of the catch through the entire processing chain. 
859 The Panel found, for example, that, for tuna pr oducts derived from tuna caught in the ETP large 
purse-seine fishery, the tuna can be traced back to the particular set in which the tuna was caught and the well 
in which it was stored, but for tuna products containing tuna caught in other fisher ies, the tuna can only be 
traced back to the vessel and trip on which it wa s caught. The Panel also highlighted the absence of a 
mechanism, in respect of tuna caught  outside the ETP large purse-seine fishery, to ensure that a particular 
certification matches and remains attached to a specific  batch of tuna throughout the production process. 
(Panel Report, paras. 7.354-7.368) WT/DS381/AB/RW 
 
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 Nevertheless, we have been able to examine th e even-handedness of the labelling conditions 
applied under the amended tuna measure in certain scenarios that would present comparably high risks to dolphins inside and outside the ETP large purse-seine fishery. We found, in this respect, that aspects of the design of the amended tuna measure reflect a lack of even-handedness. In 
particular, we considered that the determination provisions do not provide for the substantive 
conditions of access to the dolphin-safe label to be reinforced by observer certification in all circumstances of comparably high risks, and th at this may also entail different tracking and 
verification requirements than those that apply inside the ETP large purse-seine fishery. For this 
reason, it has not been demonstrated that the differences in the dolphin-safe labelling conditions under the amended tuna measure are calibrated to , or commensurate with, the risks to dolphins 
arising from different fishing methods in different areas of the oceans. Since it therefore follows 
that the detrimental impact of the amended tuna measure cannot be said to stem exclusively from 
a legitimate regulatory distinction, we find that the amended tuna measure is inconsistent with 
Article 2.1 of the TBT Agreement. 
7.3  Articles I, III, and XX of the GATT 1994 
7.3.1  Articles I:1 and III:4 of the GATT 1994 7.267.  We now turn to address whether the Panel erred in its analysis of the consistency of the 
amended tuna measure with Articles I:1 and III:4 of the GATT 1994.  
7.268.  The United States requests us to reverse the Panel's findings that the certification 
requirements and the tracking and verification requirements of the amended tuna measure are 
inconsistent with Articles I:1 and III:4.
860 The United States claims that the Panel erred in finding 
that the two sets of requirements under the am ended tuna measure: (i) provide an "advantage, 
favour, privilege, or immunity" to tuna and tuna products from other Members that is not "accorded immediately and unconditionally" to like products from Mexico, in a manner inconsistent 
with Article I:1; and (ii) accord "less favourable treatment" to Mexican tuna and tuna products 
than that accorded to like domestic products, in a manner inconsistent with Article III:4. The United States does not advance independent arguments in support of these claims, but rather 
refers back to the arguments it developed in its challenge to the Panel's alleged errors regarding 
the detrimental impact of the certification and tracking and verification requirements under Article 2.1 of the TBT Agreement.
861 In response, Mexico reiterates its claim that, instead of 
making separate findings of inconsistency with respect to each set of criteria, "the Panel should 
have analysed the amended tuna measure as a whole"862 and concluded that the measure is 
inconsistent with Articles I:1 and III:4 of the GATT 1994.863 In Mexico's view, the Panel's failure to 
make findings of inconsistency with Articles I:1 and III:4 with respect to the amended tuna 
measure as a whole amounts to legal error.864 
7.269.  Before addressing the merits of the participants' claims of error, we first recount the 
relevant analysis and findings by the Panel. 
7.270.  In setting out its analysis, the Panel noted that Article I:1 of the GATT 1994 embodies a 
"different legal standard[]" from that in Article 2.1 of the TBT Agreement.865 For the Panel, 
"whereas Article I:1 requires only an analysis of whether the conditions attached to an advantage 
detrimentally impact the competitive opportunities of imported products in the relevant market, 
Article 2.1 … requires an additional  consideration of whether any detrimental impact nevertheless 
stems exclusively from a legitimate regulatory distinction."866 The Panel noted, however, that the 
focus on the question of "whether conditions imposed on access to an advantage modify the 
conditions of competition to the detriment of imported like products" is "similar" to a detrimental 
impact analysis under Article 2.1 of the TBT Agreement, "which similarly looks to the effect of a 
                                               
860 United States' appellant's submission, paras. 43, 357, and 359 (referring to Panel Report, 
paras. 8.3.b and 8.3.c). 
861 United States' appellant's submission, paras. 357 and 359. 
862 Mexico's appellee's submission, paras. 179 and 182. 
863 Mexico's other appellant's submission, paras. 75 and 77. 
864 Mexico's other appellan t's submission, para. 72. 
865 Panel Report, para. 7.432 (referring to Appellate Body Reports, EC – Seal Products , para. 5.94). 
866 Panel Report, para. 7.432 (referring to Appellate Body Reports, EC – Seal Products , para. 5.93). 
(emphasis original) WT/DS381/AB/RW 
 
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 measure on the competitive opportunities of imported products".867 Likewise, in its analysis under 
Article III:4 of the GATT 1994, the Panel observed that, unlike Article 2.1 of the TBT Agreement, 
Article III:4 does not require a panel to examine whether the detrimental impact of a measure on competitive opportunities for like imported products stems exclusively from a legitimate regulatory 
distinction.
868 The Panel noted, however, that the "treat ment no less favourable" test under that 
provision "is very similar to the first element of the 'less favourable treatment' test in Article 2.1 of 
the TBT Agreement".869 In the light of the above, the Panel found it "appropriate" to apply the 
findings it made with respect to detrimental impact under Article 2.1 of the TBT Agreement to its 
analysis of the amended tuna measure's consistency with Articles I:1 and III:4 of the GATT 1994.
870  
7.271.  The Panel then separately examined whethe r each of the three sets of requirements under 
the amended tuna measure – the eligibility criteria , the certification requirements, and the tracking 
and verification requirements – is consistent with Article I:1.871 Similarly, the Panel conducted 
separate examinations of the consistency of ea ch of the three sets of requirements with 
Article III:4.872  
7.272.  Starting with the eligibility criteria, the Panel noted that the parties agreed that, under the 
amended tuna measure, most Mexican tuna products continue to be derived from tuna caught by 
setting on dolphins and are therefore denied access to the dolphin-safe label, while most like 
products from the United States and other Members are not derived from tuna caught by setting on dolphins and are therefore eligible for the label.
873 The Panel considered that the regulatory 
distinction between tuna products derived from tuna caught by setting on dolphins and tuna 
products derived from tuna caught by other fish ing methods "has the effect of denying [Mexican] 
tuna products a valuable market advantage (that is, access to the dolphin-safe label)".874 
Therefore, the Panel concluded that the eligibility criteria modify the conditions of competition to 
the detriment of Mexican tuna products in the US market, in a manner inconsistent with 
Articles I:1875 and III:4 of the GATT 1994.876 
7.273.   As for the certification requirements, th e Panel recalled that, in its detrimental impact 
analysis under Article 2.1 of the TBT Agreement, it had found that such requirements impose "a 
lighter burden" on tuna products derived from tuna caught outside the ETP large purse-seine fishery than on tuna products derived from tuna caught within that fishery.
877 According to the 
Panel, the imposition of an observer requirement in the ETP large purse-seine fishery, coupled with 
the absence of such a requirement in other fisheries, "in itself strongly suggests that the amended 
tuna measure imposes certain conditions on access to the dolphin-safe label on only some  tuna 
products".878 In the Panel's view, by imposing on tuna products containing tuna caught in the 
ETP large purse-seine fishery an "additional, heavier or more burdensome" condition for access to 
the dolphin-safe label than on tuna products containing tuna caught in other fisheries, the certification requirements "modif[y] the competitive opportunities of like … tuna products", 
inconsistently with Articles I:1
879 and III:4 of the GATT 1994.880 
                                               
867 Panel Report, para. 7.433. The Panel also noted th at "Mexico refer[red] to its factual allegations 
under Article 2.1 of the TBT Agreement in support of its argument under Article I:1 of the GATT 1994." (Ibid., para. 7.434 (referring to Mexico's second written submission to the Panel, para. 202)) 
868 Panel Report, para. 7.479 (referring to Appellate Body Reports, EC – Seal Products , para. 5.117). 
869 Panel Report, para. 7.481. 
870 Panel Report, paras. 7.434 and 7.495. 
871 Panel Report, sections 7.6.1.2.2.2, 7.6.1.2.2.3, and 7.6.1.2.2.4, respectively. 
872 Panel Report, paras. 7.498-7.499, 7.500-7.501, an d 7.502-7.503, respectively. The Panel reasoned 
that the segmentation of its assessment along the three sets of requirements was necessary because Mexico had articulated its claims under Articles I:1 and III:4 in  terms of the "different la belling conditions", thus 
encompassing not only the ineligibilit y of tuna products derived from tuna caught by setting on dolphins for 
access the dolphin-safe label, but also the different ce rtification and tracking and verification requirements. 
(Ibid., paras. 7.430 and 7.492) 
873 Panel Report, paras. 7.444-7.446. 
874 Panel Report, para. 7.447. See also para. 7.498. 
875 Panel Report, para. 7.447. 
876 Panel Report, para. 7.499. 
877 Panel Report, para. 7.454. 
878 Panel Report, para. 7.455. (emphasis original) 
879 Panel Report, para. 7.455. 
880 Panel Report, para. 7.501. WT/DS381/AB/RW 
 
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 7.274.  Finally, as regards the tracking and verification requirements, the Panel recalled that, in its 
detrimental impact analysis under Article 2.1 of the TBT Agreement, it had found that the requirements for tuna products containing tuna caught outside the ETP large purse-seine fishery are "less burdensome" than those for tuna products containing tuna caught within that fishery.
881 
The Panel considered that, by imposing on the latter group of products an "additional" and more 
"burdensome" condition for access to the label than on the former group of products, the tracking and verification requirements "upset the equality of competitive opportunities", inconsistently with 
Articles I:1
882 and III:4 of the GATT 1994.883 
7.275.  Based on the foregoing, the Panel made separate findings that the eligibility criteria, the 
different certification requirements, and the different tracking and verification requirements are each inconsistent with Articles I:1 and III:4 of the GATT 1994.
884 
7.276.  As the overview above shows, the Panel's analysis of the consistency of the eligibility 
criteria with Articles I:1 and III:4 somewhat differs from its analysis of the alleged detrimental impact flowing from such criteria under Articl e 2.1 of the TBT Agreement. In the context of 
Articles I:1 and III:4, the Panel assessed the extent to which the disqualification of tuna products 
derived from tuna caught by setting on dolphins affects the relative competitive conditions of Mexican, US, and other tuna products in the US market, whereas, in the context of Article 2.1, the 
Panel simply "reaffirm[ed]" the Appellate Body's alleged finding that the eligibility criteria are 
even-handed, without expressly evaluating their im pact on access to the dolphin-safe label for the 
relevant groups of like tuna products.
885 Conversely, in its separate analyses of the consistency 
with Articles I:1 and III:4 of the different certification requirements and the different tracking and 
verification requirements, the Panel's approach cl osely mirrored its approach to assessing of the 
alleged detrimental impact of each such se t of requirements under Article 2.1 of the 
TBT Agreement.  
7.277.  We recall that, in the original proceedings, the Appellate Body criticized the original panel's 
"assumption" that the claims under the TBT Agr eement and the GATT 1994 were "substantially the 
same". The Appellate Body found, for this reason, that the original panel had acted inconsistently 
with Article 11 of the DSU and exercised false ju dicial economy in refraining from ruling on 
Mexico's claims under Articles I:1 and III:4 of the GATT 1994.886 This is because, unlike Article 2.1 
of the TBT Agreement, Articles I:1 and III:4 do  not require a panel to examine whether the 
detrimental impact of a measure on competitive opportunities for like imported products stems 
exclusively from a legitimate regulatory distinction.887 Moreover, unlike in Article 2.1 of the 
TBT Agreement, the most-favoured nation obligation  in Article I:1 is not expressed in terms of 
"treatment no less favourable", but rather through an obligation to extend any "advantage" 
granted by a Member to any product originating in or destined for any other country "immediately 
and unconditionally" to the "like product" originating in or destined for all other countries.888  
7.278.  These differences notwithstanding, important parallels exist between the 
non-discrimination provisions contained in Arti cle 2.1 of the TBT Agreement and Articles I:1 
and III:4 of the GATT 1994. In particular, the in quiry under these provisions hinges on the 
question of whether the measure at issue modifies the conditions of competition in the responding Member's market to the detriment of products imported from the complaining Member vis-à-vis 
like domestic products or like products imported from any other country.
889 Accordingly, in 
assessing whether a measure affects competitive conditions under Article I:1 and/or Article III:4 of the GATT 1994, it may be reasonable for a panel to rely on any relevant findings it made in 
                                               
881 Panel Report, para. 7.463. 
882 Panel Report, para. 7.464. 
883 Panel Report, para. 7.503. 
884 Panel Report, paras. 8.3.a, 8.3. b, and 8.3.c, respectively. Subsequently, the Panel found that the 
"eligibility criteria" meet the requirements of the chapeau of Article XX of the GATT 1994 (ibid., para. 8.5.a), whereas the "certification requirements" and the "tracking and verification requirements" do not. (Ibid., paras. 8.5.b and 8.5.c, respectively) 
885 See section 7.2.2 of this Report. 
886 Appellate Body Report, US – Tuna II (Mexico) , para. 405. 
887 Appellate Body Reports, EC – Seal Products , paras. 5.93 and 5.105. 
888 Appellate Body Reports, EC – Seal Products , para. 5.81. 
889 See e.g. Appellate Body Reports, EC – Seal Products , paras. 5.88 and 5.101; Thailand – Cigarettes 
(Philippines) , para. 129; Korea – Various Measures on Beef , para. 137; US – Clove Cigarettes , para. 180;  
US – Tuna II (Mexico) , para. 215; and US – COOL , para. 268. WT/DS381/AB/RW 
 
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 examining that measure's detrimental impact under  Article 2.1 of the TBT Agreement. For these 
reasons, we do not see that the Panel's reliance, in its analyses under Articles I:1 and III:4 of the GATT 1994, on certain reasoning and findings from its analysis of detrimental impact under Article 2.1 of the TBT Agreement was, in itself, inappropriate.  
7.279.  However, we recall that we have already expressed a number of concerns with respect to 
the Panel's approach, in its analysis under Articl e 2.1 of the TBT Agreement, to assessing whether 
the amended tuna measure has a detrimental impact on Mexican tuna products in the 
US market.
890  
7.280.  First, we held that, by segmenting its analysis along the three sets of requirements under 
the amended tuna measure, the Panel failed to conduct a holistic assessment of how those various labelling conditions, taken together, adversely affect the conditions of competition for Mexican 
tuna products in the US market as compared to like US and other tuna products. Nor did the Panel 
give due consideration to the question of whether and how such detrimental impact resembles, in nature or extent, the detrimental impact that was found, in the original proceedings, to exist under 
the original tuna measure. These considerations apply equally to the Panel's analytical approach 
under Articles I:1 and III:4. In our view, the Panel's examination of relative access to the dolphin-safe label for Mexican, US, and other tuna  products should not have been limited to the 
regulatory distinction between tuna products derived from tuna caught by setting on dolphins and 
tuna products derived from tuna caught by other fishing methods. Indeed, while Mexican tuna products may be denied access to the dolphin-safe la bel by virtue of the fact that they are derived 
from tuna caught by setting on dolphins, other elements of the amended tuna measure, such as 
the "no dolphin killed or seriously injured" standard and the certification and tracking and 
verification requirements, may also exclude some tuna products of US or other origin from access to the label. Thus, the Panel should also have assessed how the certification and tracking and 
verification requirements introduced by the 2013 Final Rule for tuna products originating outside 
the ETP large purse-seine fishery had the effect of reducing (or increasing) access to the dolphin-safe label for such tuna products, thus narrowing (or broadening) the difference in 
treatment between Mexican tuna products and like US  or other products in terms of access to the 
dolphin-safe label. By failing to do so, the Pa nel's segmented analysis falls short of a proper 
examination of the extent to which the various labelling conditions under the amended tuna measure, taken together, modify the detrimental impact that was found to exist in the original 
proceedings. 
7.281.  Second, we noted that, in its discrete detrimental impact analyses regarding the 
certification and tracking and verification requirements, the Panel engaged in a comparison of a 
subset of the relevant groups of products found to be "like" in this dispute – on the one hand, 
Mexican tuna products derived from tuna caught other than by setting on dolphins; on the other hand, tuna products from the United States and other countries derived from tuna caught other 
than by setting on dolphins. We took the view that, in order to reach its conclusions on detrimental 
impact, the Panel should have, instead, compared the treatment that the labelling conditions under 
the amended tuna measure accord to the group  of Mexican tuna products, on the one hand, with 
the treatment accorded to the groups  of like tuna products from the United States and other 
countries, on the other hand. These considerations apply with equal force to the analytical 
approach adopted, and the product groups compared by the Panel in order to assess whether the certification and tracking and verification requirements discriminate against Mexican tuna products 
under Articles I:1 and III:4 of the GATT 1994. 
7.282.  For the above reasons, we consider that, in assessing whether the amended tuna measure 
modifies the conditions of competition to the detr iment of Mexican tuna products in the US market 
under Articles I:1 and III:4 of the GATT 1994, the Panel applied an incorrect approach. 
We therefore find that the Panel erred in its analysis of whether the amended tuna 
measure: (i) provides an "advantage, favour, privilege, or immunity" to tuna products from other 
Members that is not "accorded immediately and unconditionally" to like products from Mexico, in a 
manner inconsistent with Article I:1 of the GATT 1994; and (ii) accords "less favourable treatment" 
to Mexican tuna products than that accorded to like domestic products, in a manner inconsistent with Article III:4 of the GATT 1994. Accordingly, we reverse the Panel's findings, in 
paragraphs 8.3.a, 8.3.b, and 8.3.c of the Panel Re port, that the eligibility criteria, the different 
                                               
890 See section 7.2.2 of this Report. WT/DS381/AB/RW 
 
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 certification requirements, and the different trac king and verification requirements are each 
inconsistent with Articles I:1 and III:4 of the GATT 1994. 
7.283.  Having reversed these findings by the Panel, we do not consider it necessary to rule on the 
United States' claims on appeal that: (i) the Pane l improperly allocated the burden of proof under 
Articles I:1 and III:4 by making findings on the different costs and burdens imposed by the 
certification and tracking and verification requirements on suppliers of tuna products operating inside and outside the ETP large purse-seine fishery
891; (ii) the Panel erred in finding a difference 
in costs and burdens stemming from the certification and tracking and verification requirements 
and in failing to explain how any such difference modifies the conditions of competition to the detriment of Mexican tuna products
892; and (iii) the Panel did not properly establish a genuine 
relationship between the certification and tracking and verification requirements and any 
detrimental impact on Mexico's competitive opportunities in the US market.893 
7.3.2  The chapeau of Article XX of the GATT 1994 7.284.  The Panel found that the features of the amended tuna measure that gave rise to 
violations of Articles I and III relate to the goal of conserving dolphins and, accordingly, are 
provisionally justified under Article XX(g) of the GATT 1994.
894 Neither participant has challenged 
this finding on appeal.895 We therefore turn to address the clai ms of the United States and Mexico 
regarding the Panel's analysis and findings under the chapeau of Article XX of the GATT 1994. 
Before turning to address these claims, we first recount the relevant findings of the Panel. 
7.3.2.1  The Panel's findings 7.285.  In analysing the United States' defence under Article XX of the GATT 1994, the Panel 
sought to determine whether the requirements of the amended tuna measure, including its 
eligibility criteria, certification requirements, and tracking and verification requirements, are justified under Article XX(g).
896 The Panel agreed with the parties that dolphins are an "exhaustible 
natural resource"897, and considered that measures designed to reduce the harm done to dolphins 
in commercial fishing practices "concern" the protection of dolphins, and "relate to" the conservation of dolphins.
898 The Panel considered that "the amended tuna measure remains 
centrally concerned with the pain caused to dolphins in the context of commercial fishing practices 
both inside and outside the ETP, and caused by both setting on dolphins and other methods of tuna fishing."
899 The Panel therefore found that the requirements concerning eligibility, 
certification, and tracking and verification "relate to" the goal of conserving dolphins since they 
help to ensure that the US tuna market does not operate in a way that encourages fishing 
techniques that are not dolphin safe.900 The Panel therefore concluded that "the features of the 
amended tuna measure that give rise to violations of Articles I and III of the GATT 1994 are 
nevertheless provisionally justified under subparagraph (g) of Article XX [of] the GATT 1994."901 
7.286.  Turning to the chapeau of Article XX of the GATT 1994, the Panel considered that, where 
even-handedness under Article 2.1 of the TBT Agreem ent is analysed through the lens of, or using, 
the analytical framework of arbitrary or unjustifiable discrimination, it may be appropriate to rely 
                                               
891 United States' appellant's submission, paras. 357 and 359 (referring to paras. 136-144 
and 288-295). 
892 United States' appellant's submission, paras. 357 and 359 (referring to paras. 145-155 
and 314-319). 
893 United States' appellant's submission, paras. 357 and 359 (referring to paras. 167-184 
and 327-330). 
894 Panel Report, para. 7.541. The Panel exercised judicial economy in respect of the United States' 
defence under subparagraph (b) of Article XX. (Ibid., para. 7.545) 
895 In its Notice of Appeal, the United States also made a conditional request for completion of the legal 
analysis under Article XX(b) of the GATT 1994. Because th is request was contingent on Mexico appealing the 
Panel's finding that the amended tuna measure is provisionally justified under Article XX(g) of the GATT 1994 – which Mexico did not do – we need not consider the United States' request. 
896 Panel Report, para. 7.510. 
897 Panel Report, para. 7.521. 
898 Panel Report, para. 7.529. 
899 Panel Report, para. 7.533. 
900 Panel Report, para. 7.535. 
901 Panel Report, para. 7.541. The Panel exercised judicial economy in respect of the United States' 
defence under subparagraph (b) of Article XX. (Ibid., para. 7.545) WT/DS381/AB/RW 
 
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 on that reasoning in the context of assessing a measure's consistency with the chapeau of 
Article XX.902 The Panel acknowledged that, in  EC – Seal Products , the Appellate Body faulted the 
panel for automatically importing its analysis un der Article 2.1 of the TBT Agreement into its 
analysis under the chapeau of Article XX of the GATT 1994.903 The Panel in this dispute did not 
consider that this precluded reliance on Article 2.1 findings in the context of the chapeau of 
Article XX, but rather that a panel need only just ify its reliance on such findings. The Panel noted 
that its findings in the context of Article 2.1 were based on its conclusion that particular features of 
the amended tuna measure are arbitrarily discrim inatory because they are not reconcilable with 
the measure's objectives.904 Accordingly, the Panel considered that it was "appropriate" to rely on 
the reasoning it had developed in the context of Article 2.1 in the course of its analysis under the chapeau of Article XX.
905 
7.287.  The Panel separately analysed the requir ements of the amended tuna measure as they 
relate to eligibility, certification, and tracking and verification. With respect to the eligibility criteria, the Panel noted that the main regulatory distinction of the amended tuna measure does 
not concern different countries, but rather different fishing methods, and that it is the fishing 
method of setting on dolphins that is regulated differently and more tightly than other fishing methods. The Panel noted, moreover, that tuna products containing tuna caught in instances 
where a dolphin was killed or seriously injured are ineligible to be labelled dolphin safe regardless 
of what fishing method was used, and regardless of where or how the tuna was caught. The Panel agreed with the United States that the most appropriate condition to examine is the different harms to dolphins caused by setting on dolphins versus those caused by other fishing methods.
906 
The Panel recalled that setting on dolphins causes unobservable harms to dolphins beyond 
mortality and serious injury. These harms arise "as a result of the chase itself", and support the Appellate Body's conclusion in the original proceedings that setting on dolphins is "particularly 
harmful" to dolphins.
907 The Panel also noted the finding by the original panel that the observed 
and unobserved effects of setting on dolphins were "fully addressed" by the original measure precisely because it "disqualif[ied] all tuna products containing tuna harvested with that method 
from access to the 'dolphin-safe' label"
908, and that "to the extent that it would not discourage 
these unobserved effects of setting on dolphins and their potential consequences on dolphin populations … the use of the AIDCP labelling requirements … could potentially provide a lesser degree of protection than the exis ting US dolphin-safe provisions."
909 
7.288.  Applying these findings in the present case, the Panel was not convinced that fishing 
methods other than setting on dolphins cause the same or similar unobserved harms. Rather, the Panel agreed with the United States that, even if there are tuna fisheries using gear types that 
produce the same number of dolphin mortalities and serious injuries allowed or caused in the ETP, 
"it is simply not the case that such fisheries are producing the same level of unobserved harms, 
such as cow-calf separation, muscular damage, immune and reproductive system failures, which 
arise as a result of the chase in itself."
910 The Panel also observed that the Appellate Body did not 
say in the original proceedings that the United States must disqualify all other fishing methods from accessing the dolphin-safe label, or that setting on dolphins and other methods of fishing 
must be regulated in the same manner. To the contrary, the Appellate Body accepted that the 
United States is permitted to "calibrate" the requirements imposed by the amended tuna measure 
according to "the likelihood that dolphins would be adversely affected in the course of tuna fishing operations in the respective co nditions" of different fisheries.
911  
                                               
902 Panel Report, para. 7.557. 
903 Panel Report, para. 7.558 (referring to Appellate Body Reports, EC – Seal Products , para. 5.310). 
904 Panel Report, para. 7.559. 
905 Panel Report, para. 7.560. 
906 Panel Report, para. 7.577. 
907 Panel Report, para. 7.579 (referring to Appellate Body Report, US – Tuna II (Mexico) , paras. 246 
and 289). 
908 Panel Report, para. 7.580 (quoting Appellate Body Report, US – Tuna II (Mexico) , para. 287). 
909 Panel Report, para. 7.580 (quoting Original Panel Report, para. 7.613). We recall that tuna products 
may carry the AIDCP dolphin-safe label whenever no dolphin was killed or seriously injured in harvesting the tuna contained therein, even if the t una is caught by setting on dolphins. 
910 Panel Report, para. 7.581 (quoting United States' first written submission to the Panel, para. 113 
(emphasis original)). 
911 Panel Report, para. 7.582 (quoting Appellate Body Report, US – Tuna II (Mexico) , para. 286). WT/DS381/AB/RW 
 
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 7.289.  The Panel noted the parties' agreement that one of the most important factors in 
determining whether discrimination is arbitrary or unjustifiable is whether the discrimination can be reconciled with, or is rationally related to, the policy objective with respect to which the measure has been provisionally justified under  one of the subparagraphs of Article XX.
912 The 
Panel considered that the eligibility criteria are rationally related to the dolphin protection objective 
of the amended tuna measure. In the Panel's view, the fact that other fishing methods do not cause the kind of unobservable harms as those caused by setting on dolphins means that, at least 
insofar as the eligibility criteria are concerned, the conditions prevailing in fisheries where tuna is 
caught by setting on dolphins and fisheries where that method is not used are not the same. Having considered that any discrimination that the eligibility criteria cause is directly connected to the main goal of the amended tuna measure, the Panel found that this aspect of the measure is 
not inconsistent with the requirements of the chapeau of Article XX.
913 
7.290.  With respect to the certification requirements, the Panel recalled its finding that, while 
fishing methods other than setting on dolphins cause dolphin mortality and serious injury, the 
nature and degree of the interaction between tuna  fishing vessels and dolphins is different in 
quantitative and qualitative terms.914 Accordingly, there may be no need to have an observer on 
board whose sole task is to monitor the safety of dolphins during the set or other gear 
deployment. The Panel considered this sufficient to demonstrate that maintaining different 
certification requirements does not necessarily amount to unjustifiable or arbitrary discrimination, although neither is it necessarily determinative of whether the system in place in fisheries other than the ETP large purse-seine fishery – which requires certification by captains only – is balanced 
and justified within the meaning of the chapeau of Article XX.
915  
7.291.  The Panel agreed with Mexico that captains' certificates may be unreliable because 
captains may not have the technical expertise necessary to certify accurately that no dolphins 
were killed or seriously injured in a particular set or gear deployment.916 In particular, the Panel 
considered that the tasks generally expected of  a captain may be rather different from those 
involved in certifying that no dolphins were k illed or seriously injured in sets or other gear 
deployments, and captains or other crew members are not always and necessarily in possession of 
such highly specialized skills.917 In the Panel's view, the United States had not explained 
sufficiently how captains can perform the duties inherent to the certification for the dolphin-safe label since they do not appear to have the specific expertise required to do so thoroughly.
918 The 
Panel further recalled its concerns with the determination provisions due to the fact that such 
determinations are only possible in respect of certain fisheries, and the United States had not explained adequately how this limitation is rationally connected to the objectives pursued by the 
amended tuna measure.
919 
7.292.  On the basis of this analysis, the Panel considered that the findings that it had made in the 
context of Article 2.1 of the TBT Agreement applie d with equal force in the context of the chapeau 
of Article XX of the GATT 1994. The Panel considered that, insofar as the different certification 
requirements are not justified by the objective of conserving dolphins by providing consumers with 
accurate information about the dolphin-safe status of tuna products, this aspect of the amended tuna measure is unjustifiably and arbitrarily discriminatory. The Panel also stated that, unlike in 
the context of the eligibility criteria, for the purposes of this element of the measure, the 
conditions prevailing among Members are the same, because dolphins may be killed or seriously injured by all fishing methods in all oceans, and, accordingly, accurate certification is necessary 
regardless of the particular fishery in which tuna is caught. The Panel thus found that the different 
certification requirements are not applied consistently with the requirements of the chapeau of 
                                               
912 Panel Report, para. 7.583. 
913 Panel Report, para. 7.584. The Panel relied on the same reasoning to conclude that the eligibility 
criteria are applied in a manner that does not constitute a disguised restriction on trade. (Ibid., para. 7.585) 
914 Panel Report, para. 7.592. 
915 Panel Report, para. 7.593. 
916 Panel Report, para. 7.598. 
917 Panel Report, para. 7.601. 
918 Panel Report, para. 7.603. 
919 Panel Report, para. 7.604. WT/DS381/AB/RW 
 
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 Article XX.920 One of the panelists expressed a separate opinion similar to that which had been 
expressed in the context of Ar ticle 2.1 of the TBT Agreement.921 
7.293.  With respect to the tracking and verification requirements, the Panel recalled its conclusion 
that such requirements impose a lighter burden on tuna products containing tuna caught other 
than in the ETP large purse-seine fishery.922 The Panel saw merit in Mexico's arguments that the 
lighter tracking and verification requirements im posed outside of the ETP large purse-seine fishery 
may make it more likely that tuna products cont aining tuna caught by vessels other than large 
purse-seine vessels will be incorrectly labelled as dolphin safe, although it did not find it necessary 
to make a definitive finding on that point. The Panel agreed with Mexico that the lesser burden placed on tuna products containing tuna caught other than in the ETP large purse-seine fishery is not rationally related to the amended tuna measure's objective of conserving dolphins by providing 
information to consumers concerning the dolphin-safe status of tuna products. Moreover, the Panel 
considered that, to the extent that the different requirements may make it easier for tuna products containing tuna caught other than by large purse-seine vessels in the ETP to be incorrectly 
labelled, this would also be inconsistent with the measure's goal of providing accurate information 
to consumers. In the Panel's view, the United States had not provided any explanation as to how this differential treatment is related to, let alone justified by, the objectives pursued by the 
amended tuna measure. Accordingly, the Pane l concluded that the different tracking and 
verification requirements are applied in a manne r that constitutes unjustifiable and arbitrary 
discrimination, contrary to the chapeau of Article XX of the GATT 1994.
923  
7.3.2.2  Whether the Panel erred in its anal ysis under the chapeau of Article XX of the 
GATT 1994 
7.294.  The participants advance claims challenging different parts of the Panel's analysis and 
findings under the chapeau of Article XX of the GATT 1994. Mexico challenges the Panel's findings 
regarding the eligibility criteria, and requests us to  modify the reasoning of the Panel and find that 
the eligibility criteria also demonstrate that the amended tuna measure as a whole is applied in a manner that constitutes arbitrary or unjustifiable discrimination.
924 For its part, the United States 
challenges the Panel's findings regarding the certification requirements and the tracking and 
verification requirements, and requests us to reverse the Panel's findings and complete the legal analysis in this regard.
925 
7.295.  Both participants contend that the Panel erred in its analysis of whether discrimination 
occurs "between countries where the same conditio ns prevail". The Panel found that, with respect 
to the eligibility criteria, the conditions between countries are not the same.926 This finding is 
appealed by Mexico. In respect of the certificatio n requirements and the tracking and verification 
requirements, however, the Panel found that the conditions between countries are the same.927 
The United States appeals these findings of the Panel. 
7.296.  In addition, both participants advance claims of error regarding the Panel's analysis as to 
whether the discrimination is "arbitrary or unjustifiable". The Panel found that the eligibility criteria 
are directly related to the objectives of the measur e, and therefore are applied in a manner that 
meets the requirements of the chapeau.928 This finding is appealed by Mexico. Conversely, 
the Panel found that the certification requirements and the tracking and verification requirements 
                                               
920 Panel Report, para. 7.605. 
921 The panelist who wrote a separate opinion considered , contrary to the Panel ma jority's view, that the 
United States had demonstrated that the different requirements as to who mu st make a dolphin-safe 
certification are rational ly connected or calibrated to th e different risks facing dolphi ns in different areas of the 
oceans and from different fishing methods. (Panel Report, para. 7.606) The panelist agreed, however, with the majority in finding that the United States had not explained or justified the discrimination caused by the determination provisions, and would have found, for th is reason alone, that th e United States had not 
established that the certification requirements are applied consistently with the chapeau of Article XX. (Ibid., para. 7.607) 
922 Panel Report, para. 7.610. 
923 Panel Report, para. 7.611. 
924 Mexico's other appellant's submission, para. 167(d). 
925 United States' appellant's submission, para. 463. 
926 Panel Report, para. 7.584. 
927 Panel Report, para. 7.605. 
928 Panel Report, paras. 7.584 and 8.5.a. WT/DS381/AB/RW 
 
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 are not  directly related to the objectives of the measure, and therefore are applied in a manner 
that does not meet the requirements of the chapeau of Article XX.929 These findings are appealed 
by the United States. 
7.3.2.2.1  Discrimination between countries where the same conditions prevail 
7.297.  In respect of the Panel's analysis of the eligibility criteria, Mexico claims that the Panel 
erred by finding that "the conditions prevailing in fisheries where tuna is caught by setting on dolphins and fisheries where that method is not used are not the same."
930 Mexico considers this 
finding to be erroneous because, in its view, the relevant conditions are not the differences in 
unobservable harms, but rather in dolphin mortalities and serious injuries (both observed and unobserved) caused by commercial tuna fishing operations. As a result, because there are mortalities and injuries in tuna fisheries other than the ETP large purse-seine fishery, the relevant 
conditions are the same, and the Panel erred by limiting the relevant conditions to the impact of 
unobservable effects only.
931  
7.298.  The United States responds that "the relevant 'conditions' relate to all adverse effects 
suffered by dolphins, which … include not only mortality and serious injuries, but those 
unobservable harms that dolphins incur from being chased."932 Because it considers that the harm 
to dolphins occurring in the ETP large purse-seine fishery differs from the harm in other fisheries, 
the United States argues that the conditions are not the same between fisheries. Thus, the 
United States argues, since the relevant conditions are not the same, no discrimination exists for 
purposes of the chapeau, and the eligibility cr iteria are therefore justified under Article XX.933 
7.299.  In respect of the Panel's analysis of the certification and tracking and verification 
requirements, the United States claims that the Panel failed to conduct an independent 
examination of whether the requirements di scriminate between countries where the same 
conditions prevail. In the context of the certification requirements, the only condition the Panel 
cited was the fact that "dolphins may be killed or seriously injured by all fishing methods in all 
oceans", and its conclusion that "accurate certification is necessary regardless of the particular 
fishery" where tuna was caught.934 The United States asserts that the relevant condition in this 
dispute is the relative harm  (both observed and unobserved) su ffered by dolphins from different 
fishing methods in different fisheries, and that the findings in the original proceedings affirm that 
this condition is not the same in the ETP large purse-seine fishery and all other fisheries.935 Noting 
the Panel's focus on whether the differences in the education and training of observers and 
captains result in differences in the accuracy of certifications, the United States observes that the 
Panel made no "definitive finding" as to the accuracy of certifications, and that, in any event, the 
evidence on the Panel record does not support such a finding.936 The United States therefore 
considers that the Panel's analysis "is legally unsupported by the evidence on the record".937 In the 
context of the tracking and verification requirem ents, the United States maintains that the Panel 
did not even address the issue of whether thes e requirements discriminate between countries 
where the same conditions prevail.938  
7.300.  In response, Mexico argues that the Pane l correctly found that the same conditions exist 
for Mexico, the United States, and other countries because dolphins may be killed or seriously injured by all fishing methods in all oceans. Accordingly, accurate certification and tracking and 
verification are necessary regardless of the particular fishery in which tuna is caught.
939 Mexico 
disagrees with the United States' contention that the relevant conditions are the relative harm suffered by dolphins from different  fishing methods in different fisheries, and that those conditions 
are not the same in the ETP large purse-seine fishery and all other fisheries. As Mexico recalls from 
                                               
929 Panel Report, paras. 7.605, 7.611, 8.5.b, and 8.5.c. 
930 Mexico's other appellant's submission, para. 156 (quoting Panel Report, para. 7.584). (emphasis added by 
Mexico) 
931 Mexico's other appellant's submission, para. 158. 
932 United States' appellee's submission, para. 178. (emphasis original) 
933 United States' appellee's submission, para. 180. 
934 United States' appellant's submission, para. 391 (quoting Panel Report, para. 7.605). 
935 United States' appellant's submission, paras. 393-394. 
936 United States' appellant's submission, paras. 395-399. 
937 United States' appellant's submission, para. 400. 
938 United States' appellant's submission, para. 401. 
939 Mexico's appellee's submission, para. 202. WT/DS381/AB/RW 
 
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 its other appellant's submission, the relevant conditions are dolphin mortalities and serious injuries 
(both observed and unobserved) caused by commercial tuna fishing operations.940 The Panel was 
therefore "correct in finding, either explicitly or implicitly, that the amended tuna measure discriminates between countries where the same conditions prevail".
941 
7.301.  The Appellate Body has identified three an alytical elements in respect of arbitrary or 
unjustifiable discrimination in the chapeau of Article XX: (i) the application of the measure results in discrimination; (ii) the discrimination occurs between countries where the same conditions 
prevail; and (iii) the discrimination is arbitrary or unjustifiable.
942 In EC – Seal Products , the 
Appellate Body considered that the second of th ese steps "necessitates an assessment of whether 
the 'conditions' prevailing in the countries betw een which the measure allegedly discriminates are 
'the same'".943 This suggests that an assessment of whether there is discrimination between 
countries where the conditions prevailing are "the same" is both a predicate for, and necessarily 
informs, a panel's examination as to whether such discrimination is "arbitrary or unjustifiable".944 
The Appellate Body added that, in assessing which "conditions" are relevant  for purposes of 
establishing arbitrary or unjustifiable discrimination, pertinent context may be found in the 
particular subparagraph of Article XX under which a measure has been provisionally justified, and the provisions of the GATT 1994 with which a measure has been found to be inconsistent.
945 
7.302.  We do not see that the participants fundamentally differ as to the general character of the 
"conditions" that are relevant for purposes of the analysis under Article XX. Both Mexico and the United States seem to agree that the relevant conditions are, broadly speaking, harms suffered by dolphins by virtue of commercial tuna fishing operations. Rather, their disagreement appears to 
concern the degree  of specificity with which those harms should be identified, and whether, as a 
factual matter , the harms arising from setting on dolphins in the ETP large purse-seine fishery, on 
the one hand, and from other fishing methods in other fisheries, on the other hand, are similar or 
different. Mexico argues that the relevant conditions prevailing between countries are the same  
because the harms to dolphins in terms of mortality and serious injury arises irrespective of the fishing area or method used. By contrast, the United States argues that the relevant conditions 
prevailing between countries are not the same  because the harms to dolphins, in particular, the 
unobservable harms, are greater in the ETP large purse-seine fishery. In this respect, the disagreement between the participants amounts to an other iteration of their opposing positions as 
to whether the harms or risks associated with setting on dolphins in the ETP large purse-seine 
fishery are greater than those associated with other fishing methods occurring in the ETP and 
elsewhere.  
7.303.  In their arguments, however, the participants devote little attention to the underlying 
factors that inform which conditions are relevant for purposes of the Panel's analysis. Both Mexico 
and the United States refer to the Appellate Body's guidance in EC 
 Seal Products  that the 
identification of the "relevant conditions" under the chapeau may be understood by reference to 
the applicable subparagraph of Article XX under which the measure was provisionally justified, and the substantive obligations under the GATT 1994 with which a violation has been found.
946 Neither 
participant, however, provides much analysis as to how such factors favour its view over that of 
the other participant regarding the conditions that are relevant in this dispute. 
7.304.  Turning to the Panel's analysis, we first note that the Panel indeed appears to have found 
that, for purposes of its examination of the eligibility criteria , the relevant condition was the harms 
                                               
940 Mexico's appellee's submission, para. 202 (refe rring to Mexico's other appellant's submission, 
paras. 155-158). 
941 Mexico's appellee's submission, para. 203. 
942 Appellate Body Report, US – Shrimp , para. 150. 
943 Appellate Body Reports, EC – Seal Products , para. 5.299. 
944 Appellate Body Reports, EC – Seal Products , para. 5.317. 
945 Appellate Body Reports, EC – Seal Products , paras. 5.300-5.301 (referring to Appellate Body 
Reports, US – Gasoline , pp. 23-24, DSR 1996:I, pp. 21-22; and US – Shrimp , para. 150). The Appellate Body 
found uncontested that "the same animal welfare condit ions prevail in all countries where seals are hunted", 
and that the European Union had not otherwise succeeded in demonstrating that the conditions prevailing in Canada and Norway, on the one hand, and Greenland, on  the other hand, "are relevantly different". The 
Appellate Body therefore proceeded on the basis that the conditions prevailing in those countries were 
"the same" for purposes of the chapeau of Article XX. (Ibid., para. 5.317) 
946 Mexico's other appellant's submission, para. 155;  United States' appellant's submission, para. 385 
(both referring to Appellate Body Reports, EC – Seal Products , para. 5.300). WT/DS381/AB/RW 
 
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 to dolphins arising from the unobservable effects of fishing methods . As the Panel explained, 
"the fact that other fishing methods do not cause the kind of unobservable harms as are caused by setting on dolphins means that, at least insofar as the eligibility criteria are concerned, the conditions prevailing in fisheries where tuna is caught by setting on dolphins and fisheries where 
that method is not used are not the same."
947 By contrast, in its examination of the certification 
requirements, the Panel appears to have considered that the relevant condition was the harms to 
dolphins arising from death or serious injury . Here, the Panel stated that, "unlike in the context of 
the eligibility criteria, for the purposes of this element of the measure, the conditions prevailing 
among Members are the same, because dolphins may be killed or seriously injured by all fishing 
methods in all oceans, and accordingly accurate certification is necessary regardless of the particular fishery in which tuna is caught."
948 The Panel did not make any statement regarding 
conditions prevailing between countries in the context of its analysis of the tracking and 
verification requirements. 
7.305.  We have concerns with the Panel's view that the relevant conditions for certain aspects of 
the measure (the eligibility criteria) somehow differ from the relevant conditions for other aspects 
of the measure (the certification requirements), and its ultimate conclusion that the conditions are not the same  for the former, but are the same  for the latter. Article XX requires that the measure  
not be applied in a manner that constitutes arbitrary or unjustifiable discrimination between 
countries where the same conditions prevail. We therefore do not understand how the Panel c o n s i d e r e d  t h a t  d i f f e r e n t  s e t s  o f  c o n d i t i o n s  a r e  r e l e v a n t  i n  r e s p e c t  o f  d i f f e r e n t  a s p e c t s  o f  t h e  measure at issue. The Panel may have taken this approach because, as we noted in previous 
sections of our Report, the Panel seems to have  compared different sets of tuna products 
depending on the particular requirements of the measure that it was examining. That is, when it came to the eligibility criteria, the Panel compared the treatment accorded to tuna products that 
either qualified or did not qualify for the dolphin-safe label depending on whether they derived 
from tuna caught by setting on dolphins, whereas, when it turned to the certification and tracking and verification requirements, the Panel compar ed the treatment accorded to tuna products 
meeting different sets of requirements in different fisheries, but which all qualified for access to 
the dolphin-safe label. We reiterate the concern we previously expressed that the Panel's segmented analysis of the measure led it to isolat e its consideration of different elements of the 
measure without examining the manner in which those elements are interrelated, and without 
reconciling the different conclusions it drew in respect of these elements. In particular, we do not 
see on what basis the conditions relevant for the certification or tracking and verification requirements would differ from those relevant for the eligibility criteria given that, as we have 
pointed out, access to the dolphin-safe label is conditioned on the satisfaction of all of the 
conditions, including the certification and tracking and verification requirements, that are contained in the amended tuna measure. 
7.306.  Moreover, the Panel did not explain why it selected the conditions it did. We recall that the 
Appellate Body in EC – Seal Products  provided guidance on this question, noting that the 
identification of the "relevant conditions" under the chapeau may rely for pertinent context on the 
applicable subparagraph of Article XX under which the measure was provisionally justified, and the 
substantive obligations of the GATT 1994 found to be violated.
949 In this dispute, the Panel did not 
refer to subparagraph (g) in identifying the relevant "conditions" for purposes of the chapeau to Article XX. Rather, in the context of its examinat ion of the eligibility criteria, the Panel did not 
identify the relevant conditions by reference to these elements, but rather to the risks associated 
with "fisheries where tuna is caught by setting on dolphins and fisheries where that method is not 
used".950 In the context of the certification requirements, the Panel stated that, unlike in the 
context of the eligibility criteria, the conditions prevailing among Members in respect of the 
certification requirements are the same since "dolphins may be killed or seriously injured by all fishing methods in all oceans".
951  
7.307.  We note that, in the context of its analysis under Article XX(g), the Panel referred to the 
parties' agreement that dolphins are an "exhaustible natural resource"952; that one of the goals of 
                                               
947 Panel Report, para. 7.584. 
948 Panel Report, para. 7.605. 
949 Appellate Body Reports, EC – Seal Products , para. 5.300. 
950 Panel Report, para. 7.584. 
951 Panel Report, para. 7.605. 
952 Panel Report, para. 7.521. WT/DS381/AB/RW 
 
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 the US dolphin-safe labelling regime is to contri bute to the protection of dolphins; and that the 
conservation of dolphins is therefore a policy objective falling within the scope of Article XX(g).953 
The Panel added that a measure that is designed to reduce the harm done to dolphins in commercial fishing practices concerns the protection of dolphins.
954 We also recall the Panel's 
statement that "the amended tuna measure remains centrally concerned with the pain caused to 
dolphins in the context of commercial fishing practices both inside and outside the ETP, and caused by both setting on dolphins and other methods of tuna fishing."
955 In addition, the original panel 
recognized that the adverse effects on dolphins a ddressed by the US dolphin-safe provisions relate 
to observed and unobserved mortalities and serious injuries to dolphins in the course of tuna fishing operations.
956 In the context of Articles I:1 and III: 4 of the GATT 1994, the Panel examined 
the differences in treatment accorded to Mexican producers of tuna products, on the one hand, 
and US and other producers of tuna products, on  the other hand. Irrespective of the type and 
nature of the applicable requirements in the amended tuna measure, however, all such requirements seek to address the risk of harm to dolphins arising from different fishing methods in 
different areas of the oceans. 
7.308.  These factors indicate to us that the prev ailing conditions between countries are the risks 
of adverse effects on dolphins arising from tuna fishing practices. Moreover, having indicated in 
other parts of its analysis that the relevant conditions for purposes of the amended tuna measure 
are harms to dolphins arising from tuna fishing practices, it is not clear why the Panel then identified more specific conditions relating to the type or level of harm as being relevant to 
different aspects of the measure, and then found that only in respect of one of those aspects 
(namely, the eligibility criteria) the conditions differed, whereas for another aspect (namely, the 
certification requirements) the conditions were the same. We do not consider that such an analysis is consistent with the chapeau's requirement that the measure  not be applied in a manner that 
constitutes arbitrary or unjustifiable discrimination between countries where the same conditions 
prevail, or accords proper treatment to the integr ated elements of the US dolphin-safe labelling 
regime. In the circumstances of this case, we proceed on the basis that the conditions prevailing 
between countries are the same for purposes of the chapeau of Article XX of the GATT 1994. 
7.3.2.2.2  Arbitrary or unj ustifiable discrimination 
7.309.  We now turn to address the participants' claims that the Panel erred in its analysis as to 
whether the discrimination is "arbitrary or unjustifiable". 
7.310.  In respect of the Panel's analysis of the eligibility criteria, Mexico claims that the Panel 
should have focused on the policy objective reflected in Article XX(g) of the GATT 1994, rather than on the objectives of the measure.
957 Had the Panel done so, Mexico argues, then it would 
properly have focused on "the reduction of dolphin mortalities and serious injuries in all 
circumstances" rather than on the different type, nature, quality, magnitude, or regularity of the 
adverse effects.958 According to Mexico, there is no basis to "calibrate" between different levels of 
dolphin mortalities or serious injuries in achieving the policy objective under Article XX(g). Mexico 
notes that it has challenged the granting of the dolphin-safe label to tuna products produced from tuna caught by the fleets of other countries using different fishing methods in different fisheries. 
Mexico considers that evidence before the Panel and the Panel's findings "clearly establish[] that 
these other fishing methods cause observed and unobserved dolphin mortalities and serious 
injuries."
959 
7.311.  In response to Mexico's claim, the United States argues that the practice of setting on 
dolphins reflects an inherent  danger that is simply not present in other fishing methods, despite 
the fact that those other methods may also kill or seriously injure dolphins. The United States 
notes that the Panel recognized the legitimacy of drawing a distinction between fishing methods 
that have different natures, and considers that this distinction is clearly reconcilable with, and 
rationally related to, the policy objective of protecting dolphins. The United States also rejects 
                                               
953 Panel Report, para. 7.525. 
954 Panel Report, para. 7.529. 
955 Panel Report, para. 7.533. 
956 Panel Report, para. 7.528 (referring to Original Panel Report, para. 7.486). 
957 Mexico's other appellant's submission, para. 161. 
958 Mexico's other appellant's submission, para. 161. 
959 Mexico's other appellant's submission, para. 162. WT/DS381/AB/RW 
 
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 Mexico's argument that Article XX(g) does not permit Members to apply measures that are 
"calibrated" to different risks. The United States observes that, in US – Shrimp , the Appellate Body 
found that not taking into account different risk levels or conditions in different countries indicated that a measure does not meet the requirements of the chapeau.
960  
7.312.  In its appeal concerning the certification and tracking and verification requirements, the 
United States claims that the Panel misunderstood the analysis of whether discrimination is arbitrary or unjustifiable. According to the United States, the Panel erroneously considered this to 
be "a single-factor test … rather than a cumulative analysis of all the factors that could be relevant 
to making such a determination."
961 The United States contends that, by applying an overly narrow 
legal analysis, the Panel erroneously relied entire ly on its Article 2.1 analysis, and improperly 
disregarded other relevant factors. The United States advances similar arguments in respect of the 
determination provisions962 and the tracking and verification requirements.963 In addition, the 
United States argues that the Panel erred in its examination of the certification and tracking and verification requirements under the chapeau because it did not take into account the different risks 
to dolphins inside and outside the ETP large purse-seine fishery.
964 
7.313.  In response to the United States' claim, Mexico argues that the Panel was correct to focus 
on the question of whether the discrimination can be reconciled with, or is rationally related to, the 
policy objective with respect to which the measure has been provisionally justified under one of 
the subparagraphs of Article XX.965 Mexico argues that the Panel did not disregard other relevant 
factors, but gave the United States an opportunity to explain why the differential treatment was not arbitrary or unjustifiable, and the United States was unable to do so. Mexico considers that the 
Panel properly explained its reasons for concluding that, in the circumstances of this dispute, 
it was appropriate for it to rely on the reasoning it had developed in the context of Article 2.1 in its analysis under the chapeau of Article XX.
966 
7.314.  In our view, these aspects of the participants' claims raise two threshold issues in respect 
of the legal standard under the chapeau of Article XX: (i) whether the Panel was correct to focus its analysis on whether discrimination can be reconciled with, or is rationally related to, the policy 
objective of the measure; and (ii) whether the Panel was correct to rely on its findings in the 
context of Article 2.1 of the TBT Agreement in reaching its conclusions regarding Article XX of 
the GATT 1994. If the Panel was correct on both counts, then we must assess the participants' 
claims that the Panel erred in its application of the legal test that it identified.  
7.315.  First, with respect to the legal standard under the chapeau of Article XX, we note that 
Mexico and the United States challenge different aspects of the Panel's articulation of that standard. The United States argues that the Panel erred by unduly limiting its chapeau analysis to 
a "single-factor test" that focused on whether the discrimination can be reconciled with, or is 
rationally related to, the policy objective of the measure. For its part, Mexico argues that the Panel erred by focusing on the policy objective of th e measure, rather than the policy objective as 
identified in the applicable subparagraph of Article XX. 
7.316.  The Appellate Body has stated that the analysis of whether discrimination is arbitrary or 
unjustifiable "should focus on the cause of the discrimination, or the rationale put forward to explain its existence".
967 The Appellate Body has explained that such an analysis "should be made 
in the light of the objective of the measure", and that discrimination will be arbitrary or 
unjustifiable when the reasons given for the discrimination "bear no rational connection to the objective" or "would go against that objective".
968 Thus, "[o]ne of the most important factors" in 
the assessment of arbitrary or unjustifiable discrimination is the question of whether the 
discrimination can be reconciled with, or is rationally related to, the policy objective with respect to 
                                               
960 United States' appellee's submission, para. 186 (referring to Appellate Body Reports, US – Shrimp , 
para. 165; and US – Shrimp (Article 21.5 – Malaysia) , paras. 140-143). 
961 United States' appellant's submission, para. 416. 
962 United States' appellant's submission, paras. 432 and 434. 
963 United States' appellant's submission, para. 451. 
964 United States' appellant's submission, paras. 421 and 455. 
965 Mexico's appellee's submission, para. 209 (referring to Panel Report, para. 7.553). 
966 Mexico's appellee's submission, para. 211. 
967 Appellate Body Report, Brazil – Retreaded Tyres , para. 226 (referring to Appellate Body Reports,  
US – Gasoline , US – Shrimp , and US – Shrimp (Article 21.5 – Malaysia) ). 
968 Appellate Body Report, Brazil – Retreaded Tyres , para. 227. WT/DS381/AB/RW 
 
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 which the measure has been provisionally justified under one of the subparagraphs of 
Article XX.969 This factor is "particularly relevant in assessing the merits of the explanations 
provided by the respondent as to the cause of the discrimination".970 The Appellate Body has 
explained, however, that this is not the sole test, and that, depending on the nature of the 
measure at issue and the circumstances of the case at hand, there could be additional factors that 
may also be relevant to the overall assessment.971 Prior Appellate Body jurisprudence therefore 
underscores the importance of examining the qu estion of whether the discrimination can be 
reconciled with, or is rationally related to, the policy objective of the measure. In addition, 
however, depending on the nature of the measure at issue and the circumstances of the case at 
hand, additional factors could also be relevant to the analysis.  
7.317.  In this dispute, we do not see that the Pa nel provided an overly narrow articulation of the 
legal standard. The Panel itself noted that the question of rational relationship with the objective 
was "[o]ne of the most important factors", which suggests that it did not consider that such an analysis necessarily precluded the consideration of other factors. It appears that the essence of 
the United States' appeal in this regard concerns whether the Panel properly accounted for 
different levels of risk in its chapeau analysis. We do not see that the Panel's articulation of the legal standard, however, precluded such a consideration. Rather, it may be that a panel falls into 
error in applying that standard by not taking account of factors that, due to the nature of the 
measure at issue and the circumstances of the case, are relevant to the analysis. Below we return to the United States' claim as to whether the Panel properly applied an analysis under the chapeau to accommodate potentially different risk  profiles in different fisheries.  
7.318.  Similarly, we do not agree with Mexico that the Panel erred in articulating the legal 
standard as consisting of a focus on whether there is a rational relationship with the objectives of the amended tuna measure, rather than the objective reflected in Article XX(g). We do not 
understand how a focus on one of the objectives in  the subparagraphs of Article XX, rather than a 
focus on the objective of the measure, necessarily leads to the result Mexico seeks. We consider 
that such a distinction is somewhat artificial given that, by virtue of an examination of whether a 
measure is provisionally justified under one of the subparagraphs, the objective of the measure 
will already have been tested against, and will have been found to be aligned with, one of the objectives set out in Article XX. Indeed, prior find ings by the Appellate Body confirm that the focus 
is on the objective of the measure as examined in relation to the applicable subparagraph of 
Article XX.
972 We therefore do not understand how, in th e circumstances of this dispute, where the 
Panel has found that the objective of dolphin protection relates to the conservation of exhaustible natural resources, reliance on the objective of Ar ticle XX(g), rather than the measure, would yield 
a different analytical result.  
7.319.  Finally, we address the United States' argume nt that the Panel erred by relying entirely on 
its Article 2.1 analysis, rather than making the required independent analysis under the chapeau of 
Article XX. The Panel addressed this point in its Report. While it acknowledged that the 
Appellate Body had faulted the panel in EC – Seal Products for automatically importing its analysis 
under Article 2.1 into its analysis under the chapeau of Article XX, it did not consider that the Appellate Body's finding stands for the proposition that a panel can never rely on its findings under 
Article 2.1 in the context of the chapeau of Article XX.
973 Rather, if a panel seeks to rely on 
findings made under Article 2.1 in the context of the chapeau, it must justify its use of those findings. In particular, the Panel reasoned, where an Article 2.1 analysis was based entirely on the 
question of whether the measure was applied in a manner that would constitute a means of 
arbitrary or unjustifiable discrimination between countries where the same conditions prevail, a panel may apply relevant aspects of its reasoning and factual findings developed in the context of 
Article 2.1 to its analysis under the chapeau of Article XX.
974 The Panel therefore considered it 
                                               
969 Appellate Body Reports, EC – Seal Products , para. 5.306. 
970 Appellate Body Reports, EC – Seal Products , para. 5.306 (referring to Appellate Body Report,  
Brazil – Retreaded Tyres , para. 227). 
971 Appellate Body Reports, EC – Seal Products , para. 5.321. 
972 See Appellate Body Report, Brazil – Retreaded Tyres , para. 228, finding that an aspect of the 
measure "bears no relationship to the legitimate obje ctive pursued by the Import Ban that falls within the 
purview of Article XX(b), and even goes against th is objective". See also Appellate Body Reports, US – Shrimp , 
para. 165; and EC – Seal Products , para. 5.317. 
973 Panel Report, para. 7.558. 
974 Panel Report, para. 7.558. WT/DS381/AB/RW 
 
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 "appropriate … to rely on the reasoning" developed in the context of its analysis under Article 2.1 
in the course of its analysis under the chapeau of Article XX.975 
7.320.  Previously, we considered that it was appropriate for the Panel, in the context of Article 2.1 
of the TBT Agreement, to focus its analysis on  whether there is arbi trary or unjustifiable 
discrimination by assessing whether the discrimination is rationally related to, or can be reconciled 
with, the policy objective of the measure. Although we identified concerns with the Panel's application of the legal standard under Article 2.1, we did not find that the Panel erred in its 
articulation of that standard. Accordingly, we do not believe it was inappropriate for the Panel, in 
principle, to have referred to and relied on that same legal standard in the context of its reasoning under the chapeau of Article XX. We agree with the Panel that this is not an instance where a panel has simply imported its finding under Article 2.1, but rather a situation in which a panel has 
relied on a similar analytical process under the two provisions by focusing on the existence of 
arbitrary or unjustifiable discrimination. Moreover, while the panel in EC 
 Seal Products  devoted 
three sentences to its analysis under the chapeau of Article XX by reference to its findings under 
Article 2.1976, the Panel in this dispute developed a distinct analysis under Article XX and provided 
considerably more reasoning on this issue, in addition to examining other dimensions of the 
chapeau analysis that were not developed in the context of its analysis under Article 2.1.977 
7.321.  As we noted in connection with the Unit ed States' arguments above, the essence of the 
United States' claim concerns whether the Panel accounted for different levels of risks to dolphins 
in its chapeau analysis. We do not see that the Panel's articulation of the legal standard, or the 
fact that the Panel relied on reasoning it had de veloped in the context of Article 2.1, precluded 
such a consideration under the chapeau of Article XX. Below we address the United States' claim 
as to whether the Panel properly applied a chapeau analysis to accommodate potentially different 
risk profiles in different fisheries. 
7.322.  For the foregoing reasons, we do not consider that either Mexico or the United States has 
sustained their respective claims regarding the Panel's interpretation or articulation of the legal 
standard under the chapeau of Article XX, and we do not agree with the United States that the 
Panel erred in its chapeau analysis by relying on the reasoning it had developed when considering Mexico's claims under Article 2.1 of the TBT Agreement. 
7.323.  This brings us to the participants' claims as they relate to the Panel's application of the 
legal standard under the chapeau of Article XX of the GATT 1994.  
7.324.  In respect of the Panel's analysis of the eligibility criteria, Mexico maintains that the Panel 
erred because, had it properly focused its analysis on the objective of reducing dolphin mortality 
and serious injury in all circumstances, there wo uld have been no basis to "calibrate" between 
different levels of dolphin mortalities and serious injuries.
978 For its part, the United States argues 
that the opposite is true, and that the Appellate Body has found that not taking into account 
different risk levels or conditions in different countries indicates that the measure does not meet 
the requirements of the chapeau.979 
7.325.  In its examination of the eligibility criteria under the chapeau of Article XX, the Panel again 
relied on what it considered to be the Appellate Bo dy's "settled" conclusion that the United States 
is entitled to disqualify tuna products containing tuna caught by setting on dolphins from accessing the dolphin-safe label, and that the United States need not disqualify fishing methods other than 
setting on dolphins. The Panel thus cross-referenced its earlier analysis in the context of Article 2.1 
of the TBT Agreement that established, in the Pane l's view, that the Appellate Body had found that 
the eligibility criteria were not inconsistent with Article 2.1.
980 The Panel repeated its 
understanding that the Appellate Body had concluded that setting on dolphins is particularly 
harmful to dolphins due to the unobserved harms resulting from the chase itself.981 The Panel also 
                                               
975 Panel Report, para. 7.560. 
976 Panel Reports, EC – Seal Products , para. 7.650. 
977 Panel Report, paras. 7.546-7.611. 
978 Mexico's other appellant's submission, para. 161. 
979 United States' appellee's submission, para. 186 (referring to Appellate Body Reports, US – Shrimp , 
para. 165; and US – Shrimp (Article 21.5 – Malaysia) , paras. 140-143). 
980 Panel Report, para. 7.578 and fn 792 thereto (referring to paras. 7.126-7.135). 
981 Panel Report, paras. 7.579-7.581. WT/DS381/AB/RW 
 
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 recalled its view that the Appellate Body had not faulted the original tuna measure due to the 
disqualification for the dolphin-safe label arising from setting on dolphins, but rather because it did not sufficiently address the harms caused to dolphins by other tuna fishing methods.
982 According 
to the Panel, the Appellate Body accepted that, in principle, WTO law allows the United States to 
"calibrate" the requirements imposed by the amended tuna measure to "the likelihood that 
dolphins would be adversely affected in the course of tuna fishing operations in the respective conditions" of different fisheries.
983 The Panel understood this to mean that, because the 
Appellate Body found that setting on dolphins is particularly harmful to dolphins, it implicitly 
acknowledged that the United States need not im pose the same standards on all fishing methods 
in order to ensure that its regime is consistent with Article 2.1 of the TBT Agreement.  
7.326.  We recall that, in our assessment of the Panel's analysis under Article 2.1 of the 
TBT Agreement, we did not agree with the Pane l's statement that the Appellate Body in the 
original proceedings had settled that the United States is entitled to disqualify tuna products containing tuna caught by setting on dolphins from ever accessing the dolphin-safe label, and that 
it may bring its dolphin-safe labelling regime into conformity with Article 2.1 without disqualifying 
methods of tuna fishing other than setting on dolphins. We further considered that, by finding that this issue had been "settled" in the original proc eedings, the Panel precluded a proper relational 
and comparative analysis of the regulatory distinct ions and the treatment of the group of products 
that are ineligible for access to the dolphin-safe label under the amended tuna measure, as compared to the group of products that are eligible  for such access. In addition, we observed that 
the Panel's approach also prevented it from enga ging in the central question in these compliance 
proceedings, namely, a full exploration of whether the changes introduced by the United States to 
the amended tuna measure suffice to bring this measure into compliance with the recommendations and rulings of the DSB. We find  that, because these criticisms concern aspects 
of the Panel's reasoning and findings that it also relied upon in the context of its analysis under the 
chapeau of Article XX, and that we, too, consider re levant to that analysis, the Panel also erred in 
its assessment of the eligibility criteria under the chapeau. 
7.327.  In respect of the Panel's analysis of the certification and tracking and verification 
requirements, the United States advances several cl aims that are the same or similar to claims it 
raises in challenging the Panel's analysis under Article 2.1 of the TBT Agreement. Foremost among these challenges is the United States' claim that  the Panel majority erred in finding that the 
certification requirements impose arbitrary or unjustifiable discrimination because any differences 
in labelling accuracy resulting from differences in education and training between captains and observers are "calibrated" to the risks to dolphins arising from different fishing methods in 
different ocean areas.
984 In the United States' view, the Panel majority's analysis contradicts the 
principle, expressed by the Appellate Body, that "WTO law allows the United States to 'calibrate' the requirements imposed by the amended measur e" based on the different risks to dolphins 
arising in different fisheries.
985 For the United States, a Member can impose different requirements 
based on the different conditions in the areas subj ect to each type of requirement, and this is 
supported by the Appellate Body's view that not taking into account different risk levels or 
conditions in different countries indicates that the measure does not  meet the requirements of the 
chapeau.986 The United States further argues that, once it is established that the United States can 
impose different requirements to address the fact that the ETP large purse-seine fishery has a different risk profile than other fisheries, it is clear that the different certification requirements are 
justified by reference to the objective of dolphin protection.
987 In addition, the United States 
maintains that the Panel majority's finding contradicts the finding of the Appellate Body that the United States could bring itself into compliance without requiring observer certification for access 
                                               
982 Panel Report, para. 7.582. 
983 Panel Report, para. 7.582 (quoting Appellate Body Report, US – Tuna II (Mexico) , para. 286). 
984 United States' appellant's submission, para. 421. 
985 United States' appellant's submission, para. 422 (q uoting Panel Report, para. 7.582, in turn quoting 
Appellate Body Report, US – Tuna II (Mexico) , para. 286). 
986 United States' appellant's submission, para. 422 (referring to Appellate Body Reports, US – Shrimp , 
para. 165; and US – Shrimp (Article 21.5 – Malaysia) , paras. 140-143). 
987 United States' appellant's submission, para. 423. The United States argues that this point is further 
supported by the reasoning of the panelis t who wrote a separate opinion. (Ibid.) WT/DS381/AB/RW 
 
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 to the dolphin-safe label.988 The United States advances similar arguments for the tracking and 
verification requirements.989 
7.328.  For its part, Mexico does not advance any new argumentation in response to this claim by 
the United States, but rather cross-references its general argumentation in respect of the question 
of whether the Panel properly accounted for the different risks inside and outside the ETP large 
purse-seine fishery.990 We recall that, in sum, Mexico argues that the amended tuna measure is 
not saved by the fact that it accepts a higher percentage of incorrect dolphin-safe information on 
product labels to be passed to consumers with respect to tuna caught in purportedly low-risk 
fisheries (i.e. all fisheries outside of the ETP large purse-seine fishery) than for tuna caught in the purportedly high-risk fishery (i.e. the ETP large purse-seine fishery). Because the amended tuna measure's objective of "ensuring that consumers are not misled or deceived about whether tuna 
products contain tuna caught in a manner that adversely affects dolphins" is "absolute", there is 
no "acceptable" mortality or serious injury in the dolphin-safe information. Mexico argues that, in the light of the objectives of the amended tuna me asure, any proposed calibration of the different 
risks by the measure clearly results in arbitrary and unjustifiable discrimination. 
7.329.  We recall that the analysis of whether di scrimination is arbitrary or unjustifiable "should 
focus on the cause of the discrimination, or the rationale put forward to explain its existence".
991 
Indeed, as the Appellate Body has explained, "[o]ne of the most important factors" in the 
assessment of arbitrary or unjustifiable discriminat ion is the question of whether the discrimination 
can be reconciled with, or is rationally related to, the policy objective with respect to which the measure has been provisionally justified.
992 However, the relationship of the discrimination to the 
objective of a measure may not be the entire inquiry; depending on the nature of the measure at 
issue and the circumstances of the case at hand, there could be additional factors that may also be relevant to the overall assessment.
993 
7.330.  In the circumstances of this dispute, we understand this jurisprudence to support, as 
relevant for an analysis of arbitrary or unjustifiable discrimination under the chapeau of Article XX, an assessment of whether the requirements of the amended tuna measure are calibrated to the 
likelihood that dolphins would be adversely affected in the course of tuna fishing operations in the 
respective conditions. According to the United States, any differences in the regulatory requirements of the amended tuna measure are just ified by reference to the objective of dolphin 
protection because such differences reflect the differences in risks arising in different fisheries. 
Before the Panel, the United States advanced that rationale to explain why the different sets of 
requirements under the amended tuna measure do not mean that such measure is designed and applied in a manner constituting arbitrary or unjustifiable discrimination. For this reason, it was 
incumbent on the Panel to engage with that expl anation, and any evidence about the design and 
application of the measure, in order to determine whether these sufficed to demonstrate that the measure is not designed or applied in a manner that constitutes arbitrary or unjustifiable 
discrimination.  
7.331.  In its examination of the certification re quirements under the chapeau of Article XX, the 
Panel again relied on reasoning and findings it had developed in the context of Article 2.1 of the TBT Agreement. In particular, the Panel noted its agreement with Mexico's claim that captains may 
not have the technical expertise necessary to certify accurately that no dolphins were killed or 
seriously injured in a particular set or gear deployment.
994 The Panel concluded that, to the extent 
that captains cannot be assumed to have the skills necessary to make an accurate dolphin-safe 
certification, this distinction makes it easier for tuna products containing non-dolphin-safe tuna 
caught other than by a large purse-seine vessel in the ETP to be incorrectly labelled as dolphin safe.
995 On that basis, the Panel found that the Un ited States had not shown that the different 
                                               
988 United States' appellant's submission, para. 424 (referring to Appellate Body Report, US – Tuna II 
(Mexico) , para. 296). 
989 United States' appellant's submission, paras. 455-457. 
990 Mexico's appellee's submission, para. 212 (ref erring to section IV.B of its submission). 
991 Appellate Body Report, Brazil – Retreaded Tyres , para. 226 (referring to Appellate Body Reports,  
US – Gasoline ; US – Shrimp ; and US – Shrimp (Article 21.5 – Malaysia) ). 
992 Appellate Body Reports, EC – Seal Products , para. 5.306. 
993 Appellate Body Reports, EC – Seal Products , para. 5.321. 
994 Panel Report, paras. 7.598-7.601. 
995 Panel Report, para. 7.602. WT/DS381/AB/RW 
 
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 certification requirements do not impose arbitrary or unjustifiable discrimination.996 The Panel 
further recalled its finding that the determination provisions are also inconsistent with Article 2.1 because the United States had not adequately explained how the fact that the relevant 
determinations are only possible in respect of certain fisheries is rationally connected to the 
objective pursued.
997 In its examination of the tracking and verification requirements, the Panel 
again relied on reasoning and findings it had developed in the context of Article 2.1 to conclude that the lesser burden placed on producers catching tuna other than in the ETP large purse-seine 
fishery, is not rationally related to the objective of the amended tuna measure.
998 
7.332.  We recall that, in our assessment of the Pa nel's analysis of the certification and tracking 
and verification requirements under Article 2.1 of  the TBT Agreement, we found that the Panel's 
segmented approach led it to overlook the ma nner in which these requirements, when viewed 
together with the substantive conditions that limit access to the dolphin-safe label, operate 
together to further  the objectives of the amended tuna measure. We therefore considered that the 
Panel's decision to adopt a segmented analytical approach prevented it from properly applying the 
legal standard that it articulated. We also expressed our concern that the Panel's analysis was not 
clear as to whether it considered, in the context of  the different certification requirements, that the 
risk profiles of the relevant fisheries giving rise  to the different groups of tuna products are the 
same  or different . Therefore, while the concept of different risk profiles affecting dolphins in the 
relevant fisheries seems to have played some part in the Panel's analysis, we did not see that such analysis encompassed consideration of the relative risks of harm to dolphins from different fishing techniques in different areas of the oceans, or of  whether the distinctions that the amended tuna 
measures draws in terms of the different conditions of access to the dolphin-safe label are 
explained in the light of the relative risk profiles.
999 I n  r e s p e c t  o f  t h e  P a n e l ' s  a n a l y s i s  o f  t h e  
tracking and verification requirements, we observed that the Panel did not seek to identify the risk 
profiles inside and outside the ETP large purse-seine fishery, and that we were not convinced by 
the Panel's suggestion that it need not consider such risk profiles because these requirements 
relate only to circumstances occurring subsequent to the time of catch.1000 We find that, because 
these criticisms concern aspects of the Panel's reasoning and findings that it also relied upon in the context of its analysis under the chapeau of Arti cle XX, the Panel also erred in its assessment of 
the certification and tracking and verification requirements under the chapeau. 
7.3.2.2.3  Conclusion  
7.333.  We have identified a number of errors of the Panel's analysis and ultimate findings under 
the chapeau of Article XX of the GATT 1994 concer ning the eligibility criteria, certification 
requirements, and tracking and verification requirements. We do not consider that the Panel 
properly analysed whether the discrimination that exists is between countries where the same 
conditions prevail. Having examined the Panel's findings, we consider that, in this dispute, the prevailing conditions between countries are the ri sks of adverse effects on dolphins arising from 
tuna fishing practices, and that such conditions are the same for purposes of the analysis of the 
conformity of the amended tuna measure with the requirements of the chapeau. 
7.334.  With regard to whether the eligibility cr iteria resulted in arbitrary or unjustifiable 
discrimination, we consider that the Panel's analysis suffered from a similar failing to that arising 
in its analysis under Article 2.1 of the TBT Agreem ent, namely, that it categorically concluded that 
the disqualification of tuna products derived from tuna caught by setting on dolphins is a 
                                               
996 Panel Report, para. 7.603. 
997 Panel Report, para. 7.604. 
998 Panel Report, para. 7.610. 
999 We also addressed the United States' claims conc erning the Panel's analysis of the determination 
provisions, but did not find a basis for legal error. In particular, we considered that the Panel did not 
improperly make the case for Mexico in respect of the determination provisions, and that the Panel did not err in focusing on how the determination provisions ar e designed, rather than on how they are applied. 
1000 We also addressed the United States' argument  that any detrimental impact caused by the 
certification and tracking and verification requirem ents stems exclusively from a legitimate regulatory 
distinction because the parties to the AIDCP consented to  impose a unique observer  programme on their tuna 
industries. We noted that the amended tuna measure dist inguishes between several cate gories of fisheries, but 
that the AIDCP certification and tracking and verification  requirements apply only with respect to tuna caught 
in one of those categories, that is, in the ETP larg e purse-seine fishery. We noted, moreover, that the 
conditions that the amended tuna measure applies in respect of tuna caught in the ETP large purse-seine 
fishery are, in any event, not coextensive with those under the AIDCP, in particular because the AIDCP does 
not disqualify tuna caught by setting on dolphins from being eligible to be labelled "dolphin safe". WT/DS381/AB/RW 
 
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 permissible regulatory distinction without conducti ng the inherently comparative exercise needed 
to determine under what circumstances such a dist inction would be permissible. We also express 
several concerns in respect of the Panel's analysis of the certification and tracking and verification requirements, including the fact that the Panel did no t properly identify the relative risk profiles in 
different fisheries that would have permitted the Panel to assess whether the regulatory 
distinctions in the amended tuna measure are, as  argued by the United States, calibrated to the 
different risk profiles in different fisheries.  
7.335.  Furthermore, the fact that the Panel conducted a segmented and isolated analysis of the 
three sets of requirements under the amended tuna measure was also problematic in the context of an analysis under the chapeau of Article XX. Indeed, a conclusion that a particular element of the amended tuna measure results in arbitrary or unjustifiable discrimination because it is not 
balanced in relation to particular risk profiles in different fisheries may not be sustainable if other 
integral elements of the measure are also examin ed. This, in our view, underscores the importance 
of making an assessment of arbitrary or unjustifiable discrimination in respect of relevant elements 
of the measure, taking into account relevant inte rlinkages. For the foregoing reasons, we reverse 
the Panel's finding, in paragraph 8.5.a of the Panel Report, that the "eligibility criteria" are applied 
consistently with the chapeau of Article XX of the GATT 1994, as well as the Panel's discrete 
findings, in paragraphs 8.5.b and 8.5.c of the Pa nel Report, that the "certification requirements" 
and the "tracking and verification requirements" ar e each applied inconsistently with the chapeau 
of Article XX of the GATT 1994. 
7.3.3  Completion of the legal analysis 
7.336.  Having reversed the findings made by the Panel under the GATT 1994, we now turn to 
consider whether we can complete the analysis and rule on whether the amended tuna measure is consistent with the United States' obligations under the GATT 1994. As we have noted, although 
completion of the legal analysis may assist in ensuring the prompt settlement and effective 
resolution of the dispute, the Appellate Body has completed the legal analysis only when sufficient factual findings by the panel and undisputed facts on the record have allowed it to do so. 
7.3.3.1  Articles I:1 and III:4 of the GATT 1994 
7.337.  We begin with an assessment of the consistency of the amended tuna measure with 
Articles I:1 and III:4 of the GATT 1994. We observ e that, referring to the Appellate Body reports 
in EC – Seal Products , the Panel set out the four elements that must be demonstrated in order to 
establish that a measure is inconsistent with Article I:1
1001, as well as the three elements required 
to establish inconsistency with Article III:4.1002 Mexico and the United States both accept that the 
amended tuna measure satisfies all but the last of  the relevant elements that must be shown to 
establish a violation of each provision.1003 Thus, with respect to Article I:1, it remains for us to 
consider whether, under the amended tuna measure, the "advantage" of access to the dolphin-safe label that is granted to tuna products from other countries is "accorded immediately 
and unconditionally" to like Mexican tuna products. In considering this issue we also take note of, 
and agree with, the Panel's statement that the eligibility criteria and the different certification and tracking and verification requirements are "condi tions" imposed upon the "advantage" of access to 
the dolphin-safe label.
1004 As for Article III:4, we must consider whether the treatment that the 
                                               
1001 The Panel explained that establishing inconsistency with Article I:1 entails demonstrating: 
(i) that the measure at issue falls within the scope  of application of Article I:1; (ii) that the 
imported products at issue are "like" products within the meaning of Article I:1; (iii) that the measure at issue confers an "advantage, favour, pr ivilege, or immunity" on a product originating 
in the territory of any country; and (iv) that  the advantage so accorded is not extended 
"immediately" and "unconditionally" to "like" products originating in the territory of all Members. 
(Panel Report, para. 7.405 (referring to Appellate Body Reports, EC – Seal Products , para. 5.86)) 
1002 The Panel explained that establishing inconsistency with Article III:4 entails demonstrating: 
(i) that the imported and domestic products are "like products"; (ii) that the measure at issue is a "law, regulation, or requirem ent affecting the internal sale , offering for sale, purchase, 
transportation, distribution, or use" of the products at issue; and (iii) that the treatment accorded to imported products is "less favourable " than that accorded to like domestic products. 
(Panel Report, para. 7.470 (referring to Appellate Body Reports, EC – Seal Products , para. 5.99)) 
1003 Panel Report, paras. 7.424 and 7.496. 
1004 Panel Report, para. 7.442. WT/DS381/AB/RW 
 
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 amended tuna measure accords to US tuna products is "less favourable" than that accorded to like 
Mexican tuna products. 
7.338.  Notwithstanding their textual differences, Articles I:1 and III:4 are both concerned with 
protecting expectations of equal competitive opportunities for like imported products, either upon 
importation or exportation, or within a Member's market.1005 Thus, as the Panel correctly 
acknowledged1006, in this dispute the inquiry that must be conducted under both provisions must 
focus on the question of whether the amended tuna measure modifies the conditions of 
competition in the US market to the detriment of Mexican tuna products vis-à-vis US tuna 
products or tuna products imported from any other country.1007 
7.339.  We recall that, in completing the legal anal ysis under Article 2.1 of the TBT Agreement, we 
addressed the question of whether the labellin g conditions under the amended tuna measure, 
taken together, modify the conditions of competitio n to the detriment of Mexican tuna products in 
the US market.1008 We noted that, in the original proceedings, the Appellate Body relied on the 
original panel's factual findings that, "as the practices of the US and Mexican tuna fleets currently 
stand, most tuna caught by Mexican vessels … would not be eligible for inclusion in a dolphin-safe 
product under the US dolphin-safe labelling provisions", while "most tuna caught by US vessels is potentially eligible for the label".
1009 We further took the view that the Panel's factual findings in 
these compliance proceedings do not go against those original findings. Indeed, we observed that 
the regulatory distinction between tuna products derived from tuna caught by setting on dolphins and tuna products derived from tuna caught by other fishing methods, which remains unchanged from the original tuna measure, "has the effect of denying" Mexican tuna products access to the 
dolphin-safe label.
1010 Further, we did not see any Panel findings or uncontested evidence on the 
record indicating that the positions of tuna products from the United States or other countries in terms of access to the dolphin-safe label have changed as a result of the certification and tracking 
and verification requirements introduced by the 2013 Final Rule for tuna products derived from 
tuna caught outside the ETP large purse-seine fishery. Finally, we noted the participants' agreement that the amended tuna measure modi fies the conditions of competition to the 
detriment of Mexican tuna products in a manner similar to the original tuna measure.
1011 In the 
light of the above, we concluded that, by excludin g most Mexican tuna products from access to the 
dolphin-safe label, while granting conditional access to such label to like products from the United States and other countries, the amended tuna measure modifies the conditions of 
competition to the detriment of Mexican tuna products. 
7.340.  In our view, the same cons iderations apply to the issue of  whether the labe lling conditions 
under the amended tuna measure, taken together, discriminate against Mexican tuna products in a 
manner inconsistent with Articles I:1 and III:4 of the GATT 1994. Accordingly, we find that, by 
excluding most Mexican tuna products from access to the dolphin-safe label, while granting 
conditional access to such label to like products from the United States and other countries, the 
amended tuna measure: (i) provides an "advanta ge, favour, privilege, or immunity" to tuna 
products from other countries that is not "accorded immediately and unconditionally" to like products from Mexico, and is therefore incons istent with Article I:1 of the GATT 1994; and 
(ii) accords "less favourable treatment" to Mexican tuna products than that accorded to like 
domestic products, and is therefore inconsistent with Article III:4 of the GATT 1994.  
7.3.3.2  Article XX of the GATT 1994 7.341.  We now turn to address whether we can complete the legal analysis in respect of the 
defence of the United States under Article XX of the GATT 1994. A respondent seeking to justify its 
measure under this provision bears the burden of  demonstrating that the measure qualifies under 
                                               
1005 See Appellate Body Reports, EC – Seal Products , paras. 5.88 and 5.101. 
1006 See Panel Report, paras. 7.426 and 7.477. 
1007 See e.g. Appellate Body Reports, EC – Seal Products , paras. 5.88 and 5.101;  
Thailand – Cigarettes (Philippines) , para. 129; and Korea – Various Measures on Beef , para. 137. 
1008 See supra , paras. 7.234-7.238. 
1009 Appellate Body Report, US – Tuna II (Mexico) , para. 234 (quoting Original Panel Report, 
para. 7.317). 
1010 Panel Report, para. 7.447. See also para. 7.498. 
1011 See e.g. Mexico's first written submission  to the Panel, paras. 223-227 and 231-232; and 
United States' appellant's submission, para. 329 (referri ng to Mexico's response to Panel question No. 57, 
paras. 146 and 155). See also Panel Report, paras. 7.115 and 7.446. WT/DS381/AB/RW 
 
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 one of the subparagraphs of Article XX, and that  it satisfies the requirements of the chapeau.1012 
As we noted, the Panel found that the features of the amended tuna measure that gave rise to 
violations of Articles I and III "relate to" the goal of conserving dolphins and, accordingly, are provisionally justified under Article XX(g).
1013 Neither participant has appealed this finding by the 
Panel. 
7.342.  Regarding the requirements of the chapeau, we focus first on whether the amended tuna 
measure entails arbitrary or unjustifiable discrimination. The Appellate Body has previously stated 
that a measure is applied in a manner constituting arbitrary or unjustifiable discrimination when 
the application of the measure results in discrimination between countries where the same conditions prevail, and such discrimination is arbitrary or unjustifiable.
1014 As we noted, the 
amended tuna measure excludes most Mexican tuna products from access to the dolphin-safe 
label by virtue of the disqualification of tuna caught by setting on dolphins, while granting 
conditional access to such label to tuna products from the United States and other countries. This difference in treatment arises due to the distin ction drawn by the amended tuna measure between 
the treatment accorded to tuna products derived from tuna caught by setting on dolphins in the 
ETP large purse-seine fishery, and that accorded to tuna products derived from tuna caught by other fishing methods outside that fishery. We therefore consider that the relevant discrimination 
for purposes of the chapeau of Article XX is that consisting of the distinctions drawn in the 
measure between these different fishing methods in different areas of the oceans.
1015 As we also 
found above, the same conditions between countries prevail, namely, the risk of adverse effects on dolphins arising from tuna fishing practices.  
7.343.  We turn to consider whether the discrimination is arbitrary or unjustifiable. We recall that 
the analysis of whether discrimination is arbitrary or unjustifiable "should focus on the cause of the discrimination, or the rationale put forward to explain its existence".
1016 Indeed, as the 
Appellate Body has explained, "[o]ne of the most  important factors in the assessment of arbitrary 
or unjustifiable discrimination is the question of whether the discrimination can be reconciled with, or is rationally related to, the policy objective with respect to which the measure has been 
provisionally justified".
1017 However, the relationship of the discrimination to the objective of the 
measure is not the sole test; depending on the nature of the measure at issue and the circumstances of the case at hand, there could be additional factors that may also be relevant to the overall assessment.
1018 
7.344.  In examining the Panel's approach to analysing arbitrary or unjustifiable discrimination 
under the chapeau of Article XX, we considered re levant the question of whether the requirements 
of the amended tuna measure are calibrated to any differences in risks to dolphins inside and 
outside the ETP large purse-seine fishery. Accordin g to the United States, any differences in the 
regulatory requirements of the amended tuna meas ure are justified by reference to the objective 
of dolphin protection because such differences are calibrated to reflect the differences in risks in 
different fisheries.1019 Given that the United States advanced that rationale to justify the existence 
of any discrimination in the regulatory requirements of its measure, we must examine that explanation, the design of the measure, as well as any factual findings or uncontested facts relating to its application in order to determin e whether these demonstrate that the measure does 
not result in arbitrary or unjustifiable discrimination.
1020  
                                               
1012 Appellate Body Report, US – Gasoline , pp. 22-23, DSR 1996:I, pp. 20-21. 
1013 Panel Report, para. 7.541. The Panel exercised judicial economy in respect of the United States' 
defence under subparagraph (b) of Article XX. (Ibid., para. 7.545) 
1014 Appellate Body Report, US – Shrimp , para. 150. 
1015 The Appellate Body has remarked that the nature and quality of th e discrimination relevant under 
the chapeau is different from that in the treatment of products found to be inconsistent with one of the 
substantive obligations of the GATT 1994, but that this do es not mean that the circumstances that bring about 
the discrimination that is to be examined under the chapeau cannot be the same as those that led to the finding of a violation of a substantive provision of the GATT 1994. (Appellate Body Reports, EC – Seal Products , 
para. 5.298) 
1016 Appellate Body Report, Brazil – Retreaded Tyres , para. 226 (referring to Appellate Body Reports,  
US – Gasoline ; US – Shrimp ; and US – Shrimp (Article 21.5 – Malaysia) ). 
1017 Appellate Body Reports, EC – Seal Products , para. 5.306. 
1018 Appellate Body Reports, EC – Seal Products , para. 5.321. 
1019 Appellate Body Report, US – Tuna II (Mexico) , para. 282 . 
1020 Panel Report, para. 7.505. WT/DS381/AB/RW 
 
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 7.345.  We are mindful that there are both simila rities and differences between the analyses under 
the chapeau of Article XX of the GATT 1994 and Article 2.1 of the TBT Agreement.  
In EC – Seal Products , the Appellate Body noted parallels between the two legal standards, in 
particular, the fact that the concepts of "arbitrary or unjustifiable discrimination between countries 
where the same conditions prevail" is found both  in the chapeau of Article XX of the GATT 1994 
and in the sixth recital of the preamble of the TBT Agreement.1021 At the same time, the 
Appellate Body recognized differences between the analyses required under Article 2.1 and under 
the chapeau of Article XX, including the fact th at the legal standards applicable under the two 
provisions differ.1022 
7.346.  In these Article 21.5 proceedings, the Pane l examined the relationship between Article 2.1 
of the TBT Agreement and the chap eau of Article XX of the GATT 1994.1023 The Panel considered 
that, where a panel has found, in the context of Article 2.1, that a measure is not even-handed 
because it is applied in manner that would constitute a means of arbitrary or unjustifiable discrimination, it will generally be appropriate for that panel to use the reasoning underlying that 
finding in its analysis under the chapeau. The Panel noted the caution expressed by the 
Appellate Body in  EC – Seal Products , and the fact that the Appellate Body faulted that panel for 
importing its analysis under Article 2.1 into its analysis under the chapeau of Article XX. According 
to the Panel, however, the Appellate Body's ruling  does not stand for the proposition that a panel 
can never rely on its findings under Article 2.1 in the context of the Article XX chapeau, but rather that it must justify the use of such findings. The Panel thus considered that nothing in the Appellate Body's reasoning precludes a panel from applying relevant aspects of its reasoning 
developed in the context of Article 2.1 of the TB T Agreement to its analysis under the chapeau of 
Article XX of the GATT 1994. 
7.347.  We agree that, so long as the similarities and differences between Article 2.1 of the 
TBT Agreement and Article XX of the GATT 1994 are taken into account, it may be permissible to 
rely on reasoning developed in the context of one agreement for purposes of conducting an 
analysis under the other. The Panel itself conducted its analyses under Article 2.1 and Article XX 
on the basis of a legal test developed in the context of assessing arbitrary or unjustifiable 
discrimination, namely, whether the discrimination can be reconciled with, or is rationally related to, the policy objective with respect to which the measure has been provisionally justified. We note, in this regard, that the United States has consistently maintained that any differences in 
treatment under the amended tuna measure are justified by reference to the objective of dolphin 
protection because such differences reflect the diff erences in, or are calibrated to, the risks arising 
in different fisheries. 
7.348.  Moreover, we previously recalled that, as compared to the original tuna measure, the 2013 
Final Rule did not alter the disqualification from the dolphin-safe label for tuna products derived from tuna caught by setting on dolphins; rather, it introduced into the amended tuna measure 
additional requirements that apply exclusively outside the ETP large purse-seine fishery, the 
principal of which were the new requirements: (i) that captains certify in every area of the ocean, and irrespective of the fishing method used, that no dolphins were killed or seriously injured; and (ii) that all dolphin-safe tuna be segregated from non-dolphin safe tuna from the time of the catch 
through the entire processing chain.
1024 We further agreed with the Panel's view that the new 
provisions requiring certification of dolphin mortality or serious injury for all tuna products address the specific concern identified by the Appellate Body and "move[] the amended measure towards 
compliance with WTO law".
1025 Thus, to the extent that these requirements serve to enhance the 
capacity of the amended tuna measure to "address adverse effects on dolphins resulting from the 
use of fishing methods predominantly employed by  fishing fleets supplying the United States' and 
                                               
1021 Appellate Body Reports, EC – Seal Products , para. 5.310 (referring to Appellate Body Reports,  
US – Clove Cigarettes , para. 173; and US – Tuna II (Mexico) , para. 213). 
1022 On that basis, the Appellate Body in EC – Seal Products  found that the Panel erred in applying the 
same legal test to the chapeau of Article XX as it applied under Article 2.1 of the TBT Agreement. (Appellate Body Reports, EC – Seal Products , para. 5.313) 
1023 Panel Report, paras. 7.555-7.560. See also paras. 7.79-7.92. 
1024 As we noted, in fisheries other than the ETP la rge purse-seine fishery, the amended tuna measure 
also introduces an observer requirement in the event of a determination by the NMFS Assistant Administrator 
that observers are qualified and authorized to certify th at there are "no dolphins killed or seriously injured", 
and, in the non-ETP purse-seine fishery, "no setting on  dolphins", when such observers are already on board 
the vessel. 
1025 Panel Report, para. 7.141. WT/DS381/AB/RW 
 
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 other countries' tuna producers"1026 outside the ETP large purse-seine fishery, they may be said to 
respond to the "calibration" of the dolphin-safe la belling regime that the Appellate Body found was 
lacking in the original tuna measure. In assessing whether the amended tuna measure results in arbitrary or unjustifiable discrimination due to the manner in which it addresses the relative 
adverse effects on dolphins arising outside the ETP large purse-seine fishery as compared to those 
inside that fishery, it would be important to ex amine what Panel findings or undisputed evidence 
exists on the Panel record regarding the different  risk profiles in these different fisheries. 
7.349.  As we observed in the context of our completion of the legal analysis under Article 2.1 of 
the TBT Agreement, both the United States an d Mexico adduced considerable arguments and 
evidence in this dispute concerning the nature and scope of the relative harms to dolphins, both observed and unobserved, associated with differe nt fishing methods. In our view, however, the 
Panel did not examine the relative  observed  harms associated with setting on dolphins in the 
ETP large purse-seine fishery versus other fishing practices outside that fishery. In fact, the Panel's analysis made clear that its conclusion rested solely on its finding that the unobserved  harms 
differed between setting on dolphins and other fi shing methods. This approach by the Panel was 
followed in its analysis under the chapeau of Arti cle XX. In this context, the Panel reiterated its 
view that fishing methods other than setting on dolphins do not cause the same or similar 
unobserved harms as setting on dolphins.
1027 
7.350.  As we explained, the limited scope of the Panel's conclusion is important in two respects. 
First, the disagreement between the parties re garding whether the amended tuna measure is 
properly calibrated rested on fundamentally di fferent premises concerning the risk profiles 
associated with different fishing practices. The Un ited States asserted that the risks associated 
with fishing practices other than setting on dolphi ns produced "nowhere near the observed dolphin 
mortality or serious injury that setting on dolphins does"1028, whereas Mexico maintained that the 
observed mortality or serious injury from fishing practices other than setting on dolphins was 
"equal to or greater"1029 than that associated with setting on dolphins. The parties also disagreed 
regarding the nature and extent of unobserve d harms. The United States contended that 
tuna-dolphin association and related unobserved harms are unique to the ETP large purse-seine 
fishery1030, whereas Mexico maintained that such association also occurs outside the ETP, and that 
unobserved harms also result from fishing methods other than setting on dolphins.1031 By failing to 
consider the relative risks posed by different fishing methods in respect of observed  mortality or 
serious injury, while focusing solely on the narrower difference in the respective risk profiles 
attributable to unobserved  harms, the Panel never resolved the question of the overall levels of 
risk in the different fisheries, and how they comp ared to each other, notwithstanding that both 
parties had addressed such comparative risk prof iles in their pleadings in support of their 
arguments regarding arbitrary or unjustifiable discrimination under the chapeau of Article XX. We note, in this regard, that, at the oral hearing in this appeal, both Mexico and the United States 
criticized the Panel for focusing on too narrow a range of harms and, in particular, for not dealing 
with the observed harms. 
7.351.  Second, arriving at a conclusion in respect of the relative  risk profiles attributable to 
different fisheries, including both in respect of observed and unobserved harms, was, in our view, 
particularly important given that the very issue the Panel was seeking to address was whether the 
new requirements of the amended tuna measure, which apply exclusively to fisheries other than 
the ETP large purse-seine fishery, adequately addre ss the risks of harm to dolphins arising in such 
fisheries. Moreover, the princi pal additional requirements  namely, that a captain must certify 
that there were no dolphins killed or seriously injured, and that documentary proof that tuna has 
been segregated into dolphin-safe and non-dolphin safe storage areas must be made available – 
both seek to enhance the manner in which the me asure addresses the risks of observed mortality 
or serious injury outside the ETP large purse-seine fishery. Yet, the Panel never sought to compare 
the relative  harms in respect of observed  mortality or serious injury. Instead, the Panel reached a 
conclusion only on the basis of a comparative assessment of unobserved  harms. On the basis of 
the foregoing concerns, we do not consider that the Panel put itself in a position to conduct an 
                                               
1026 Appellate Body Report, US – Tuna II (Mexico) , para. 292. 
1027 Panel Report, para. 7.581. 
1028 United States' second written submission to the Panel, para. 201. See also United States' first 
written submission to the Panel, para. 236. 
1029 Mexico's first written submission to the Panel, paras. 13, 263, 248, and 306. 
1030 United States' first written submission to the Panel, paras. 85 and 338-339. 
1031 Mexico's first written submission to the Panel, para. 248. WT/DS381/AB/RW 
 
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 assessment of whether the amended tuna measure is even-handed in addressing the respective 
risk profiles of setting on dolphins in the ETP large purse-seine fishery versus other fishing methods outside that fishery.  
7.352.  In our completion of the legal analysis under Article 2.1 of the TBT Agreement, we noted 
some additional considerations regarding the assessment of different risk profiles that are also 
relevant here. Noting that the original tuna measure did not require any certification outside the ETP regarding dolphin mortality or serious injury, we recalled the Appellate Body's conclusion that, 
while the original tuna measure fully addressed the adverse effects on dolphins resulting from 
setting on dolphins in the ETP, it did "not address mortality (observed or unobserved) arising from fishing methods other than setting on dolphins outside the ETP".
1032 We noted that, in these 
circumstances, it was reasonable to consider that , irrespective of any differences in the relative 
risks, the original tuna measure did not address the incidence of harms arising from practices 
other than setting on dolphins. The Appellate Body stated that, " even accepting  that the fishing 
technique of setting on dolphins is particularly harmful to dolphins", it was not persuaded that the 
measure is even-handed as argued by the United States.1033 We observed, however, that, in these 
Article 21.5 proceedings, the question as to the relative risks associated with different fishing practices in different areas of the oceans has become more acute. Given that the amended tuna 
measure introduced a requirement outside the ETP large purse-seine fishery that captains certify 
that no dolphins were killed or seriously injured, and that, for that purpose, segregation of dolphin-safe and non-dolphin-safe tuna must be maintained, the exercise of gauging whether these new requirements are sufficient to address the risks posed to dolphins outside the ETP large 
purse-seine fishery requires a more thorough underst anding of the relative risk profiles inside and 
outside that fishery. Moreover, as we have no ted, the parties presented conflicting accounts, 
supported by considerable arguments and evidence, as to why the relative risks of observed 
mortality or serious injury do or do not justify the differences in regulatory treatment inside and 
outside the ETP large purse-seine fishery provided for under the amended tuna measure.  
7.353.  Although we did not discount the difficulty associated with making such an assessment of 
the respective risks, particularly in the light of the highly contested evidence adduced by the 
parties, we considered that the Panel's limited an alysis did not permit it to gauge properly the 
overall relative risks or levels of harm arising in different fisheries. In the absence of a proper assessment by the Panel of the relative risks exis ting inside and outside the ETP large purse-seine 
fishery, the Panel limited its ability to determine whether the discriminatory aspects of the 
amended tuna measure can be explained as being properly tailored to, or commensurate with, the differences in such risks in the light of the obje ctive of protecting dolphins from adverse effects 
arising in different fisheries. For similar reasons, the Panel's limited analysis in respect of the 
relative risk profiles in turn constrains our ability to complete the legal analysis in this regard. 
7.354.  In completing the legal analysis under Ar ticle 2.1 of the TBT Agreement, we went on to 
examine other features of the amended tuna meas ure that are not dependent on an assessment of 
the relative risks associated with different fishing methods in different areas of the oceans. In particular, we examined the determination provisions, which provide that, outside the ETP large purse-seine fishery, a requirement to provide certifications by observers may be triggered in 
scenarios where the risks of harm to dolphins in the form of mortality or serious injury would be 
comparably high to those existing in the ETP large purse-seine fishery. We recalled, in that context, the Panel's finding that the determination provisions are "an integral part" of the 
"certification system" under the US dolphin-safe labelling regime.
1034 Depending on the category of 
fishery concerned, when certain determinations have been made by the NMFS Assistant Administrator, then, in addition to the required captain certification(s), the amended tuna measure 
also conditions access to the dolphin-safe label on the provision of a certification by a qualified and 
approved observer in respect of the conditions, where applicable, of "no setting on dolphins" and 
"no dolphins killed or seriously injured". In particular, such observer certification is required if the NMFS Assistant Administrator has made a determination for a specific fishery: (i) within the 
non-ETP purse-seine fishery, that there is a regular and significant tuna-dolphin association, 
                                               
1032 Appellate Body Report, US – Tuna II (Mexico) , para. 297 (quoting Original Panel Report, 
para. 7.544). 
1033 Appellate Body Report, US – Tuna II (Mexico) , para. 297. (emphasis added) 
1034 Panel Report, para. 7.257. WT/DS381/AB/RW 
 
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 similar to the tuna-dolphin association in the ETP; or (ii) within "all other fisheries"1035, that there 
is a regular and significant mortality or serious injury of dolphins.1036  
7.355.  Like the Panel, however, we also observed that the determination provisions leave a "gap", 
in that they do not appear to address other scenarios in which there may be heightened risks of 
harm to dolphins associated with particular fishing methods outside the ETP large purse-seine 
fishery.1037 As noted, the determination provision applicable to the non-ETP purse-seine fishery 
allows for the addition of a requirement for observer certification when there is a determination of 
"regular and significant association", but does not provide for a determination of "regular and 
significant mortality or serious injury" to be made or to trigger a requirement for observer certification in that fishery.
1038 This is difficult to explain given that an observer certification is 
required in the ETP large purse-seine fishery, and that such a determination on the basis of 
"regular and significant mortality or serious injury" can be made pursuant to the other relevant 
determination provision, which is applicable to "all other fisheries".1039 In our view, this 
discrimination between the requirements applicable inside and outside the ETP large purse-seine 
fishery in instances where the harms to dolphins are similar is difficult to reconcile with the 
objective of protecting dolphins from harm. We recalled, in this regard, the Panel's finding that captains, in comparison to observers, do not necessarily and always have the technical skills 
required to certify that no dolphins were killed or seriously injured.
1040 
7.356.  In that context, we also did not consider convincing the explanations of the United States 
as to why this determination provision accounts for regular and significant association, but not for regular and significant mortality or serious injury. In particular, we expressed the concern that 
requiring purse-seine vessels to certify that they have not engaged in setting on dolphins due to 
the presence of regular and significant associat ion does not address the risks that had been 
identified by the Appellate Body concerning the us e by such vessels of other fishing methods, such 
as using FADs.
1041 Moreover, the amended tuna measure co ntemplates the existence of risks of 
mortality or serious injury in the absence of setting on dolphins, given that the determination provision linked to regular and significant mortality or serious injury applies in "all other fisheries" 
existing both inside and outside the ETP. We saw no reason that this determination provision 
should be designed to prevent the possibility of tr iggering the addition of an observer requirement 
for non-setting on activities in the non-ETP purs e-seine fishery, when such a requirement already 
exists for non-setting on activities in the ETP large purse-seine fishery and, upon a determination, 
in "all other fisheries". Moreover, this seemed of special relevance given the Appellate Body's 
statement that, although adding an observer certification that no dolphins were killed or seriously injured may not be the only way for the United States to calibrate its dolphin-safe labelling 
provisions to the risks of fishing methods other than setting on dolphins in the ETP large 
purse-seine fishery, "such a requirement may be appropriate in circumstances in which dolphins face higher risks of mortality or serious injury."
1042  
7.357.  As for the determination provision that applies in "all other fisheries", we see some merit 
in the United States' contention that the more relevant consideration in respect of a tuna-dolphin association is whether there is a vessel that is capable of intentionally targeting and taking advantage of that association, and which would thereby produce the observed and unobserved 
harms to dolphins that are linked to the fishing method of setting on dolphins. Like the 
United States, we recognize that the fisheries to which this determination provision applies do not concern the operation of large purse-seine vessels, which are the only vessels that are recognized 
                                               
1035 We recall that the category of "all other fisherie s" includes non-purse-seine vessels in any fishery 
and small purse-seine vessels in the ETP. 
1036 We further noted that the amended tuna measur e also provides, in fisheries other than the 
ETP large purse-seine fishery, for an observer certif ication where observers are determined by the NMFS 
Assistant Administrator to be qualified and authorized to certify that there are "no dolphins killed or seriously injured", and, for non-ETP purse-sein e vessels, "no setting on dolphins", and such observers are already on 
board the vessel for other reasons. 
1037 Panel Report, para. 7.263. As the Panel explained, by virtue of the determination provisions, 
"fisheries other than the ETP large purse seine fishery may be treated differently, and less stringently, under 
the amended tuna measure even where the conditions in that fishery mirror those in the ETP large purse seine fishery, either in terms of the leve l of dolphin mortality or the degree of tuna-dolphin association." (Ibid.) 
1038 Section 1385(d)(1)(B)(i) of the DPCIA; Section 216. 91(a)(2)(i) of the implementing regulations. 
1039 Section 1385(d)(1)(D) of the DPCIA; Section 216.91(a)(4)(iii) of the implementing regulations. 
1040 Panel Report, para. 7.233. 
1041 Appellate Body Report, US – Tuna II (Mexico) , para. 292. 
1042 Appellate Body Report, US – Tuna II (Mexico) , fn 612 to para. 296. WT/DS381/AB/RW 
 
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 as capable of setting on dolphins. At the same time, we also take note of the Panel's view that, 
wherever dolphins associate with tuna, "they are mo re likely to interact with tuna fishing gear, 
even if such interaction is accidental or unintentional".1043 For this reason, the Panel considered 
that, even for fishing methods that do not deliberately target the association of dolphins with tuna, 
"the risk of mortality or serious injury is necessarily heightened"1044 where there is association and 
that, accordingly, "observers may be necessary whenever there is a 'regular and significant' tuna-dolphin association, regardless of whether the association occurs in a purse seine fishery or 
any other type of fishery".
1045 It is also not clear to us whether the association of dolphins and 
tuna necessarily heightens the risk to dolphins from non-purse-seine fishing methods, nor whether any such heightened risk could be fully addressed by a determination that there is "regular and significant mortality or serious injury". To the extent that there may in fact be a heightened risk to 
dolphins due to association, comparable to that existing in the ETP large purse-seine fishery, even 
where the fishing methods employed are not capabl e of setting on dolphins, and that such risks 
could not be addressed by a determination of "regular or significant mortality or serious injury", 
we would consider this to be relevant to an assessment of the even-han dedness of the amended 
tuna measure. 
7.358.  Finally, we note that our analysis regarding the determination provisions is premised on 
the existence of risks outside the ETP large purse- seine fishery that are comparably high to the 
risks existing in the ETP large purse-seine fishery.
1046 As the Panel explained, the determination 
provisions "appear to be designed to enable the United States to impose conditions on fisheries other than the ETP large purse seine fishery where the conditions in the former approach those of 
the latter".
1047 We recall from our discussion of the measure at issue that there are differences 
between the documentation requirements existing  inside and outside the ETP large purse-seine 
fishery in respect of segregation.1048 We also recall that the Panel found that the differences in the 
tracking and verification requirements are such th at there are differences in the depth, accuracy, 
and degree of government oversight that is legally required under the amended tuna measure with respect to tuna products derived from tuna caught in the ETP large purse-seine fishery, on the one 
hand, and from tuna caught in all fisheries other than the ETP large purse-seine fishery, on the 
other hand.
1049 In such circumstances, we would expect that any determination outside the ETP 
large purse-seine fishery would entail not only the heightened certification requirements, but also tracking and verification requirements that work together with and reinforce certification in 
addressing this heightened risk. 
7.359.  In conclusion, in the absence of a proper assessment by the Panel of the respective risks 
posed to dolphins inside and outside the ETP large purse-seine fishery, we are unable to complete 
the legal analysis and assess fully whether all of the regulatory distinctions drawn under the 
                                               
1043 Panel Report, para. 7.261. According to the Panel, "the more dolphins there are in the vicinity, the 
more likely [it is] that one or more dolphins will be killed or seriously injured." (Ibid.) 
1044 Panel Report, para. 7.261. 
1045 Panel Report, para. 7.262. 
1046 We note that the determination provisions may also aim at addressing situations where the risks to 
dolphins are comparably high to thos e associated with the other fishing me thod that is disqualified from access 
to the dolphin-safe label, namely, large-scale driftnet fishing in the high seas. 
1047 Panel Report, para. 7.263. The panelist who wrote a separate opinion also cited the determination 
provisions as an example of where the amended tuna measure "enable[s] the United States to impose the 
same requirements in fisheries where the same degree of risk prevails". (Ibid., para. 7.280) 
1048 We noted in our discussion of the measure at issue that the regime for segreg ation of tuna caught in 
the ETP large purse-seine fishery is supported by docume ntary requirements consisti ng of separate TTFs, one 
of which is used to record information regarding each dolphin-safe tuna set, and another to record the same 
information in respect of non-dolphin- safe sets. All tuna caught by US-fla gged large purse-seine vessels fishing 
in the ETP must be accompanied by th ese TTFs, and importers of tuna or t una products containing tuna caught 
by non-US-flagged ETP large purse-se ine vessels must provide the TTF numbers when submitting the required 
import documents. Moreover, the TTFs  or TTF numbers accompany the rele vant tuna from the time of catch 
throughout the fishing and production  process. We further noted that all fisheries outside the ETP large 
purse-seine fishery are required to segregate dolphin- safe and non-dolphin-safe tuna from the time of the 
catch through the entire processing chain. 
1049 The Panel found, for example, that, for tuna pr oducts derived from tuna caught in the ETP large 
purse-seine fishery, the tuna can be traced back to the particular set in which the tuna was caught and the well 
in which it was stored, but for tuna products containing tuna caught in other fisher ies, the tuna can only be 
traced back to the vessel and trip on which it wa s caught. The Panel also highlighted the absence of a 
mechanism, in respect of tuna caught  outside the ETP large purse-seine fishery, to ensure that a particular 
certification matches and remains attached to a specific  batch of tuna throughout the production process. 
(Panel Report, paras. 7.354-7.368) WT/DS381/AB/RW 
 
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 amended tuna measure can be explained and justified in the light of differences in the relative 
risks associated with different methods of fishing for tuna in different areas of the oceans. Nevertheless, we have been able to examine whether or not the labelling conditions applied under the amended tuna measure constitute arbitrary or unjustifiable discrimination in certain scenarios 
that would present comparably high risks to dolp hins inside and outside the ETP large purse-seine 
fishery. We find, in this respect, that aspects of the design of the amended tuna measure are difficult to reconcile with the objective of protecting dolphins from harm. In particular, we consider 
that the determination provisions do not provide for the substantive conditions of access to the 
dolphin-safe label to be reinforced by observer certification in all circumstances of comparably high risk, and that this may also entail different tracking and verification requirements than those that apply inside the ETP large purse-seine fishery. Thus, the United States has not demonstrated that 
these aspects of the amended tuna measure do not constitute arbitrary or unjustifiable 
discrimination within the meaning of the chapeau of Article XX. For all of these reasons, it has not been established that the amended tuna measure is justified under Article XX of the GATT 1994. 
7.360.  Consequently, in addition to finding that the amended tuna measure is inconsistent with 
Article I:1, and with Article III:4, of the GATT 1994, we find that it has not been demonstrated 
that the amended tuna measure is applied in a manner that does not constitute arbitrary or 
unjustifiable discrimination; and, thus, that the amended tuna measure is not justified under 
Article XX of the GATT 1994.  
8  FINDINGS AND CONCLUSIONS 8.1.  For the reasons set out in this Report, the Appellate Body: 
a. with respect to Article 2.1 of the TBT Agreement: 
i. finds that the Panel erred in the application of Article 2.1 in its analysis of whether 
the amended tuna measure modifies the conditions of competition to the detriment 
of Mexican tuna products in the US market; 
ii. finds that the United States has not established that the Panel erred in its articulation 
of the relevant legal standard for the purposes of assessing whether the detrimental 
impact of the amended tuna measure on Mexican tuna products stems exclusively 
from a legitimate regulatory distinction; 
iii. finds that the Panel erred in finding that, in the original proceedings, the 
Appellate Body settled the issue of whether the eligibility criteria are even-handed; 
iv. finds that the Panel erred in the application of Article 2.1 in its analysis of whether 
the detrimental impact of the certification requirements and the tracking and 
verification requirements on Mexican tuna products stems exclusively from a 
legitimate regulatory distinction; 
v. finds that the United States has not established that the Panel erred in its 
assessment of whether the determination provisions are even-handed; 
vi. finds that neither Mexico nor the United States has established that the Panel acted 
inconsistently with its duty to conduct an objective assessment of the matter 
pursuant to Article 11 of the DSU in its analyses of the consistency of the eligibility criteria and the certification requirements  with Article 2.1 of the TBT Agreement; 
vii. reverses the Panel's finding, in paragraph 8.2.a of its Report, that the eligibility 
criteria do not accord less favourable treatment to Mexican tuna products than that 
accorded to like products from the United States and to like products originating in 
any other country, and are thus consistent with Article 2.1, as well as the Panel's 
discrete findings, in paragraphs 8.2.b and 8.2.c of its Report, that the different certification requirements and the differen t tracking and verification requirements 
each accord less favourable treatment to Mexican tuna products than that accorded 
to like products from the United States and to like products originating in any other country, in violation of Article 2.1; and WT/DS381/AB/RW 
 
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 viii. completes the legal analysis and finds: that the amended tuna measure modifies the 
conditions of competition to the detriment of Mexican tuna products in the 
US market; that such detrimental impact does not stem exclusively from a legitimate regulatory distinction; and, thus, that the amended tuna measure accords less 
favourable treatment to Mexican tuna products as compared to like tuna products 
from the United States and other countries and is therefore inconsistent with Article 2.1 of the TBT Agreement; 
b. with respect to Articles I:1 and III:4 of the GATT 1994: 
i. finds that the Panel erred in the application of Articles I:1 and III:4 in its analyses of 
whether the amended tuna measure provides an "advantage, favour, privilege, or 
immunity" to tuna products from other countries that is not "accorded immediately 
and unconditionally" to like products from Mexico, in a manner inconsistent with 
Article I:1 of the GATT 1994, and of whether that measure accords less favourable treatment to Mexican tuna products than that accorded to like domestic products, in 
a manner inconsistent with Article III:4 of the GATT 1994; and 
ii. reverses the Panel's discrete findings, in paragraph 8.3 of its Report, that the 
eligibility criteria, the different certification requirements, and the different tracking 
and verification requirements are each inconsistent with Articles I:1 and III:4 of the 
GATT 1994; 
c. with respect to the chapeau of Article XX of the GATT 1994: 
i. finds that the Panel erred in the application of the chapeau of Article XX in its 
analyses of whether the eligibility criteria, the different certification requirements, 
and the different tracking and verification requirements are each applied in a manner that constitutes a means of arbitrary or unjustifiable discrimination between 
countries where the same conditions prevail; and 
ii. reverses the Panel's finding, in paragraph 8.5.a of its Report, that the eligibility 
criteria are applied in a manner that m eets the requirements of the chapeau of 
Article XX, as well as the Panel's discrete findings, in paragraphs 8.5.b and 8.5.c of 
its Report, that the different certification requirements and the different tracking and 
verification requirements are each applied in a manner that does not meet the requirements of the chapeau of Article XX; and 
d. in completing the analysis under the GATT 1994: 
i. finds that the amended tuna measure is inconsistent with Article I:1, and with 
Article III:4, of the GATT 1994; and 
ii. finds that it has not been demonstrated that the amended tuna measure is applied in 
a manner that does not constitute arbitrary or unjustifiable discrimination and, thus, 
that the amended tuna measure is not justified under Article XX of the GATT 1994. 
8.2.  The Appellate Body concludes that the Un ited States has not brought its dolphin-safe 
labelling regime for tuna products into conformity with the recommendations and rulings of the DSB. The Appellate Body recommends that the DSB request the United States to bring its 
measure, found in this Report, and in the Panel Report as modified by this Report, to be 
inconsistent with the TBT Agreement and the GATT 1994, into conformity with its obligations under 
those agreements. WT/DS381/AB/RW 
 
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Signed in the original in Geneva this 2nd day of November 2015 by: 
 
 
 
  
 _________________________ 
 Shree Baboo Chekitan Servansing  Presiding Member 
 
  
 
 
 
  
 _________________________  _________________________  
 Ujal Singh Bhatia Yuejiao Zhang 
 Member Member 
 
__________