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
Document: Report of the Appellate Body
Date: 20 November 2015
Document codes: WT/DS381/AB/RW
Complainant: Mexico
Respondent: U.S.
Third parties: Australia, Brazil, Canada, China, Ecuador, EU, Guatemala, India, Japan, South Korea, New Zealand, Norway
Dispute stage: Implementation & Compliance
Agreements cited: Art. I:1, III:4  GATT 1994Art. 2.1, 2.2, 2.3, 2.4  Technical Barriers to Trade (TBT)

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

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 Modified 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)

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

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)

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

CASES CITED IN THIS REPORT
Short Title Full Case Title and Citation
Argentina – Hides and
Leather
Panel Report, Argentina – Measures Affecting the 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 August 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 – Measures 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-Dumping Duties on High-Performance
Stainless Steel Seamless 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 Publications 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/DS395/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 – Measures 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 – Anti-Dumping Duties on
Imports of Cotton-Type Bed Linen from India – Recourse to Article 21.5 of the
DSU by India, WT/DS141/AB/RW, adopted 24 April 2003, DSR 2003:III,
p. 965

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 2011:VII, p. 3995
EC – Fasteners (China) Panel Report, European Communities – Definitive Anti-Dumping Measures on
Certain Iron or Steel 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 October 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 – Anti-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 Certain 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 Safeguard 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 States – 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

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 – Countervailing Duties on Certain
Corrosion-Resistant Carbon Steel 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 Existence 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/DS384/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 Article 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 Goods 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

Short Title Full Case Title and Citation
US – Shrimp Appellate Body Report, United States – Import Prohibition 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 Prohibition 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 Certain 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 Canada – 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 – Restrictions on Imports of Tuna, DS29/R,
16 June 1994, unadopted
US – Tuna (Mexico) GATT Panel Report, United States – Restrictions 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 from 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 Affecting 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

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 1385 5 (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. Hogarth 7 (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 resulted from the adoption, on 13 June 2012, by the
DSB of the Appellate Body report (WT/DS381/AB/R) and the panel report (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 clarified that its claims under 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 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).
8 Panel Report, para. 1.10 (referring to Appellate Body Report, US – Tuna II (Mexico), para. 172).

panel and the Appellate Body referred to these measures, collectively 9, 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 States 13, 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 Program 19 (AIDCP) dolphin- safe definition
and certification were a relevant international standard 20, 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 analysing 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 dolphins, 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.
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.
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).

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, while 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 DSU 38 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 market is not used to encourage fishing fleets to catch tuna in a manner that
adversely affects dolphins", was a legitimate objective within the meaning of Article 2.2 of the TBT Agreement.
Furthermore, the Appellate Body rejected Mexico's request to find the original 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 Agreement 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 authorization 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.

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 tuna measure nullifies or impairs
benefits that accrue to Mexico under the GATT 1994 within 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
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 elements 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 Panel 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 requirements … 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).

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.

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 2015 67, 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 dispute. For purposes of this
appeal, we have interpreted this action as a notification 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,

66 The Appellate Body noted, in particular, 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.

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 "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.

 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.

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 sentences of footnote 50 to
paragraph 29 are enclosed within double square brackets, indicating that these sentences are BCI.

impaired by the extensive redaction of text said to contain BCI from the Panel's reasoning with
respect to the tracking and verification requirements 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 treatment 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 requirements is "hampered" by the Panel 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 Panel as "crucial" to its assessment. (European Union's
third participant's submission, para. 52 (quoting Panel Report, para. 7.561)) The European Union remarks that
its ability to participate as a third participant has been significantly curtailed, and, referring 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 redacted 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 arrangements 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 third 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 that 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 includes 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.

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 the 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 legal 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 contains aspects that remain unchanged from the original measure. (Ibid.,
para. 7.39 (quoting Appellate 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., paras. 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 (Article 21.5 – Brazil), para. 41.
87 Appellate Body Report, Canada – Aircraft (Article 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" – may 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.

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 complainant that failed to make out a prima facie case in the
original proceedings regarding an element of the measure 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 proceedings." (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
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.

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 implementing 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 perishable 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')". (Original Panel Report, para. 4.17)
103 Aspects of the MMPA and the DPCIA were challenged 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 adopted. 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 Salvador, 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 submission, 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 efforts 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.)

6.5. Within this area of the ocean 108, 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 westward 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), Guatemala, 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 America". (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 Modified 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 adopted by the parties to the AIDCP on 20 June 2001.
114 Original Panel Report, para. 2.39. The objectives 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 tuna 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 minimizing bycatch and discards of
juvenile tuna and non-target species. (Article II of the AIDCP (Original 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 defined 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).

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 thereafter 128, 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 serious 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 challenged 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. (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 finding was that tuna products containing tuna caught by setting on dolphins
could be labelled dolphin-safe provided that the other conditions 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 Secretary of Commerce was overruled in Earth Island Institute v. Evans, on the
basis that the Secretary failed to conduct statutorily mandated studies and that the best available scientific
evidence did not support the Secretary's finding. The ruling 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 captain and an IDCP-approved observer certify both that
there was "no setting on dolphins" and that there were "no dolphins killed or seriously injured". (Panel Report,
para. 3.19. See also Original Panel Report, paras. 2.15-2.20; and Appellate Body Report, US – Tuna II
(Mexico), paras. 175-176)

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 seas 129, the amended tuna measure
distinguishes among three general categories of fisheries 130: (i) large purse-seine131 vessels in the
ETP132 (the ETP large purse-seine fishery); (ii) purse-seine vessels outside the ETP 133 (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, the 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 Agriculture 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 AIDCP, US law, and the reports in the original
proceedings, it would use the term "large purse-seine vessel" to refer to purse-seine vessels in the ETP with a
carrying capacity greater than 363 metric tons, and the term "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" certification 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 observer certification(s) is also
triggered where the NMFS Assistant Administrator has determined that observers are qualified and authorized
to make the necessary certification(s), and such observers 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.

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 establishing the TTVP are mainly contained in CFR Title 50,
Section 216.24, and Sections 216.91-216.93 of the implementing 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 applicable conditions. (Panel Report, para. 3.26
(referring to Original Panel Report, para. 2.31))
140 Panel Report, paras. 3.50-3.51. Thus, 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 captain or the observer, where applicable, should designate
separate wells, and any commingling of dolphin-safe and non-dolphin-safe 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 trucks, storage facilities, or carrier vessels 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 implementing 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-safe tuna or tuna products and may not share the same storage containers,
cookers, conveyers, tables, or other canning and labelling 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 Panel 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 during 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 fishery 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-seine net in a fishery where a determination of regular
and significant association between dolphins and tuna has 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.

processing of tuna for sale in the US market. The relevant provisions provide for checks to be
performed on the operation of US canneries 147, 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 proceedings 150, 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 216.93(e) of the implementing regulations. Tuna
processors must submit reports on all tuna received at the processing facilities containing information about,
inter alia, species, condition, weight, ocean area, catcher vessel, 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 tuna 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 relevant certifications, forms, 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.

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 observer 159 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 harvested 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 (Original 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 regulations. 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, well 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 Mexico'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 dolphin 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 first 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 first written submission to the Panel, paras. 85-88).

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 vessel 168 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 distinction 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 provide 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 necessary 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))

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 applicable to this category of fisheries correspond
to those for tuna caught by purse-seine vessels outside the ETP.179
6.2 Principal modifications under 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 Panel 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 already 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 vessel 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,
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 government official that an
IDCP-approved observer was on board the vessel during the entire trip during which the tuna was caught.

determinations made by the NMFS Assistant Administrator 181, 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 specific 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 fishery 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-purse-seine fishery, that there was a regular and significant
mortality or serious injury of dolphins. 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.

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 verification 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 requirements 195, 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 appellant's submission, para. 66.
187 Mexico's other appellant's submission, paras. 65-66.
188 Mexico's other appellant's submission, para. 66.
189 Mexico's Notice of Other Appeal, para. 5; other appellant's submission, 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 making 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 Report, para. 8.1; and Appellate Body Report, US – Tuna II
(Mexico), paras. 407.
197 Panel Report, paras. 7.11-7.12. (emphasis original)

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 (quoting 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).

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 nature 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 consideration 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 Panel, 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 detrimental 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 clear and cognizable claim of detrimental impact separate from
the detrimental impact identified by Mexico as the result 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,
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 claim regarding the "measure as a whole" focuses on
and is most closely tied to the Panel's analysis of detrimental impact.

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 measure 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 regarding 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 (chapeau 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 Panel nevertheless recommends that the DSB request the United States
"to bring its measure … found to be inconsistent with Article 2.1 of the TBT Agreement and Articles I:1
and III:4 of the GATT 1994 and not justified 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 "might have opted for a more
holistic approach to the measure at issue by examining 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 approach. (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.

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 inconsistency 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 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".
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 regulations, for example, identifies three conditions that
must be met for the dolphin-safe label to be used for tuna products containing tuna caught in the ETP large
purse-seine fishery, the first of which 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 the 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, and 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 issuance of regulations to implement the statutory
requirements, "including regulations to establish a tracking and verification program that provides for the
effective tracking of tuna labelled under [Section 1385(d)]".

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 related 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, tuna 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
228 Panel Report, para. 7.33.
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.

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, however, 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.

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,
238 Appellate Body Report, US – Clove Cigarettes, para. 180. See also Appellate Body Reports,
239 Appellate Body Report, US – Clove Cigarettes, paras. 182 and 215. See also Appellate Body Reports,
240 Appellate Body Report, US – Clove Cigarettes, para. 182. See also Appellate Body Report,
241 Appellate Body Report, US – Clove Cigarettes, para. 192.
242 Appellate Body Reports, US – Clove Cigarettes, para. 193; US – Tuna II (Mexico), para. 215;
243 Appellate Body Report, US – Tuna II (Mexico), para. 225.

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 assertion 254, 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
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 parties 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 accorded 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
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

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 life or health, of the environment, or for the
prevention of deceptive practices, at the levels it considers 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 international 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 – because, 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', and thus the detrimental 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.

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 case 267 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 fashion 269, 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 the 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 inconsistency before examining
the responding party's defence and evidence." (Appellate 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 rather than reflecting discrimination." (Ibid., para. 284 (emphasis omitted))

the burden of proof 275, 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, for 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 requirements in fact stem exclusively 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 that, 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 Article 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 (referring 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.

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, establish "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 Appellate Body Report, US – Tuna II (Mexico),
para. 284).
289 Mexico's appellee's submission, para. 44.
290 Mexico's other appellant'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 submission, para. 11. (emphasis omitted)
294 European Union's third participant's submission, para. 12. The European Union points, in particular,
to the "significant commercial value" of the dolphin-safe label in the US market; the "asymmetry" in treatment
between tuna caught in the ETP large purse-seine fishery and tuna caught in other fisheries; 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 "private choices" on the part of US consumers and the
Mexican fleet. (Ibid., paras. 9 and 12)

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 submission, 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. This 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.

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.

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 analysis 320, 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 f ir s t , M e xic o
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 submission to the Panel, para. 68.
319 United States' first written submission to the Panel, para. 223. (emphasis original)
320 United States' second written submission 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 second written submission to the Panel, para. 117).
(emphasis omitted)
327 Panel Report, para. 7.108.
328 Panel Report, section 7.5.2.2.
329 Panel Report, para. 7.118.

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 methods 331
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.
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 Mexico'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] enormous barrier to entry' into the
US tuna market, and may cost hundreds of millions of dollars." (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).

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 verification 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.
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 applied 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 the 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 comments on United States' response to Panel question
No. 43, para. 172).

"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.
365 Appellate Body Reports, US – COOL, para. 269 (quoting, respectively, Appellate Body Reports,
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).

"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 addressing the manner in which they operate together
to modify the conditions of competition 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.
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 tracking 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)

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 would not be practically relevant "if it is assumed that it

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 caught by other fishing methods, 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 changes 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 parties did adduce evidence regarding the levels of dolphin mortality and serious injury
in fisheries other than the ETP large purse-seine fishery. The Panel might 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 panel 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 GATT 1994, the Panel did consider 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 "has the 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 products from the United States and other countries that are
excluded from access to the label by virtue of the new certification 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
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)

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 derive from tuna caught in the ETP large purse-seine
fishery, whereas most like products from the United States and 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.

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 label 398 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, prevent 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 dolphin-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 necessary 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 products derived from tuna caught other than by setting on
dolphins to the United States. (See United States' appellant'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 cautioned, a panel should not "ascribe undue weight to the
effect of a technical regulation in any hypothetical scenario". (Appellate Body Reports, US – COOL
(Article 21.5 – Canada and Mexico), para. 5.16 (emphasis omitted))

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 the detrimental impact on imported products
stems exclusively from a legitimate 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 three 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 regulatory distinction. Since all three challenges are premised on the same
contention by the United States, we examine them together. (United States' appellant's submission, paras. 25,
36, 192, 257, 264, and 334)
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).

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 methods 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
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).

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 chapeau 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 (referring 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 (referring 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 Panel further considered that the Appellate Body's approach in
US – Clove Cigarettes "closely resembles the type of analysis conducted 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." (Ibid., para. 7.92 (referring to Appellate Body Report,
US – Clove Cigarettes, para. 225))

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 jurisprudence 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 Agreement 431,
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' appellant's submission, para. 36.
428 Panel Report, para. 7.91.
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;

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 meaning 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
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 life or health, of the environment, or for the
prevention of deceptive practices, at the levels it considers 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 meaning 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.

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 (referring 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.
447 United States' appellant's submission, paras. 36, 54, 416, and 432.
448 Appellate Body Reports, US – COOL, para. 271.

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 the 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 (referring 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)

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 used 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 specific criteria or indicia through which the fairness of a
technical regulation should be assessed are not comprehensively 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 Report, para. 7.95 (emphasis original))

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 Appellate 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 verification 465 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 setting 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 setting 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.

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 Report 472, 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 dolphin-safe status of tuna is less reliable
than observer certification, the amended tuna measure's system of captain self-certification in respect of tuna
caught outside the ETP large purse-seine fishery "does 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 referring. Nevertheless, the Panel'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 purse-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.

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 methods 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 United 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 respect 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).

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 from 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 different 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 Mexico's second written submission to the Panel,
paras. 248 and 263). Mexico did not advance these arguments to show that the amended tuna measure is not
"calibrated", but rather in support of its argument that the qualification for "dolphin-safe" 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 the 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 concerned with the accuracy of information provided to
consumers." (Mexico's second written submission to the Panel, para. 173) For Mexico, "[t]una is either
dolphin-safe or it is not – eligibility for the dolphin-safe label cannot be viewed as a relative assessment."
(Ibid.)

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.
498 Panel Report, para. 7.122.
499 Panel Report, para. 7.123.

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 Article 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 posed to dolphins by those methods. (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 original proceedings". (Ibid., para. 7.135)
502 Mexico's other appellant's submission, para. 93.
503 Mexico's other appellant's submission, para. 92.
504 Mexico's other appellant's submission, para. 90.
505 Mexico's other appellant's submission, para. 93 (quoting Panel Report, para. 7.119).
506 United States' appellee's submission, 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.

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 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, [were] calibrated to the likelihood that dolphins would be adversely affected 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.

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 properly 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 addressed, 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 respect 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.

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 Appellate 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 label 527;
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-handedness 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 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."
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 eligibility criteria in the original proceedings.
7.2.3.2.3 The certification and tracking 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 (quoting 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.

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 address 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-handedness 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 first 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 because of possible civil and criminal penalties. (Ibid.,
para. 7.202)

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.
551 Panel Report, para. 7.241.

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 the Panel majority as set out in paragraphs 7.233-7.246
of the Panel Report. Instead, in a separate opinion, this panelist expressed the view that any detrimental
treatment caused by the different certification requirements does stem exclusively from a legitimate regulatory
distinction, and accordingly is not inconsistent 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 necessarily tolerated. This panelist emphasized that, provided that the tolerated
margin of error is "calibrated" to the risks faced by dolphins 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 all 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 that the extent to which a particular instance of
detrimental treatment is reconcilable with, or explicable 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.

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 methods 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 different 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 requirement "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 States. In such scenario, the Panel 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 following 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 response to the different risk profiles existing in
different fisheries, as established by the evidence.
567 United States' appellant's submission, para. 340 (quoting Appellate Body Report, US – Tuna II
568 United States' appellant's submission, para. 205. (fn omitted)

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 accuracy – 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.

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 ing 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 appropriate 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.

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 methods 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 requiring certification by an observer, rather than by a captain, "may be
appropriate in circumstances in which dolphins face higher risks of mortality or serious 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.

fisheries, on the other hand, are "calibrated" to the likelihood that dolphins would be adversely
affected in the course of tuna fishing 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 legitimate 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 example, 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.

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 certification 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 treatment 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.

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 would 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 different risks to dolphins does not appear to have guided the Panel's
analysis in the context of its analysis of Mexico's claim 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 regarding the respective "harms" to dolphins within the ETP
large purse-seine fishery as compared to other fisheries. (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 and marine mammals, including dolphins, outside of the
ETP, 'dolphins in the Atlantic, Indian, and western Pacific Oceans [do not associate with tuna] as systematically
as they do in the Eastern Tropical Pacific'." (Ibid. (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.
606 Panel Report, para. 7.244.

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 different 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 and differences in risks may not be reflected in and
relevant to all stages of the capture and subsequent 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-handedness 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 requirements expressly discusses the notion of "risk profile" and how that applies to the
different fisheries in the present dispute, using the term "calibration". (Panel Report, paras. 7.276 and 7.282)
However, we do not necessarily see that, in assessing the even-handedness of the different certification
requirements, this panelist made a complete assessment of the different 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 fishery ["particularly harmful" versus "as a general matter, significantly less
serious" in fisheries other than the ETP large purse-seine fishery], it is … entirely even-handed for the
United States to tolerate a smaller margin of error in that latter fishery, and accordingly to require observers in
that fishery but not in others." (Ibid., para. 7.258)
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 not necessarily and always have the technical skills
required to certify that no dolphins 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.
(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)

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.

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 States' response to Panel question No. 59, para. 295).
618 Panel Report, para. 7.259.
619 Panel Report, para. 7.260.
620 Panel Report, para. 7.261.
621 Panel Report, para. 7.263.

even-handedness.623 Moreover, although one panelist had disagreed with the Panel majority
regarding the even-handedness of the different certification 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
r e a s o n i n g a n d t o d e c i d e w h i c h e v i d e n c e o n t h e r e c o r d t h e y w i s h t o r e l y u p o n i n r e a c h i n g t h e i r
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.
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 (referring to Mexico's responses 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
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.

case for the complainant 636, 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 proceedings 639, 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 proof 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,
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.

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 question 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 United 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,
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.

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 are tied to the United States' argument that the
amended tuna measure's requirements for independent observers are "calibrated" 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.

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 reached its conclusion in respect of the determination
provisions "without any regard for the evidentiary record". (United States' appellant's submission, para. 235)
674 Mexico's other appellant's submission, subheading V.B.2.c(i).
675 Mexico's other appellant's submission, subheading V.B.2.c(ii).

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 submission, 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.
EC – Hormones, para. 132; EC – Sardines, para. 299; Japan – Apples, paras. 221-222; Korea – Dairy,
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.

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 was 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 found 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 panel was that 'various adverse impacts
can arise from setting on dolphins, beyond observed mortalities.'" The United States also indicates that "the
original panel had found that, while there was some uncertainty regarding 'the extent' of these impacts, the
U.S. evidence had established a presumption that 'genuine concerns exist' in that respect." (United States'
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).
699 Panel Report, para. 7.121.
701 Panel Report, para. 7.122.
702 Mexico's other appellant's submission, para. 117.

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 added; 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.

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, para. 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.

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 finding "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 given 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 consequences 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.

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 measure 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 proceedings 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, para. 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, and that the USDOC has designated the Atlantic Pelagic
Longline fishery as a "Category I" fishery due to frequently documented interactions with marine mammals.
(Ibid., para. 149 (referring to Mexico's first 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 (quoting Panel Report, para. 7.209; and referring to
para. 7.596).
731 Mexico's other appellant's submission, para. 139.

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.
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 concluded 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)

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 establish that it is unlikely that captains accurately
report dolphin mortality or serious injury. (Panel Report, para. 7.210)
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 (referring to Panel Report, fn 134 to para. 7.46).
757 United States' appellee's submission, para. 156 (referring 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 submission, para. 159 (referring to Anderson, Cetaceans and Tuna
Fisheries). (emphasis original)

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 acknowledge 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 prevalence 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 first 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 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).
767 Mexico's other appellant's submission, 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 submission, para. 145 (quoting Anderson, Cetaceans and Tuna Fisheries,
p. 67).

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 submission, para. 145 (quoting Anderson, Cetaceans and Tuna Fisheries,
p. 67).
773 Mexico's other appellant's submission, 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.

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 rulings 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, Mexico had explained to the original panel that it was limiting its claims to
tuna products, and the participants confirmed at the oral hearing that the claims 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,
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.

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, National 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 (referring to and quoting Mexico's response to Panel
question No. 57, paras. 155 and 146, respectively). We recall 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).
789 Given that the 2013 Final Rule introduced additional 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.

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, because, 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 designed or applied in a manner 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"; 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.

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 different 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

797 Panel Report, para. 7.141.
798 Panel Report, para. 7.141.
799 As we have noted, in fisheries 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 qualified 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 differences in regulation to address differences in risks
to dolphins arising in different fisheries. We do not see that such a contention differs in substance from
Mexico's position that, because there are no differences in harms to dolphins arising in different 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' appellee'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.

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 programmes, 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 the 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 longline fishing estimates that over 18,000 dolphins are killed annually 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 Indian 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 (observed 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 and 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 two dolphin stocks in the ETP – 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 Panel 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 submission 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,
808 United States' first written submission to the Panel, 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)).

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 dolphins 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 year 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 estimated 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) purse-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 indicators 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 Panel question No. 15, para. 82. The United 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 Summarizing 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 submission 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 Guidelines 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 scientific 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),
815 Panel Report, para. 7.129 (referring to Mexico's first written submission to the Panel, section III.A).

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.
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
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.

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 original 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 sets 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 "objective, scientifically-established" benchmark – such
as potential biological removal (PBR) levels – that could 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 the insufficiency of PBR data across fisheries 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 objective indicators might assist in an assessment of whether regulatory
differences in the treatment of different fisheries can be explained on the basis that such treatment is
calibrated to, or commensurate with, the relative risks to dolphins arising from different fishing methods in
different areas of the oceans.

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 fishery in terms of their depth, accuracy, and degree
of government oversight 831 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 certification(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 "the relevant factual evidence 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.

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, and 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 also 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 that 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 association 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 'regular and significant,' and has the Department of Commerce 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 implementing 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 systematically and routinely chased and encircled each year in
significant numbers by tuna fishing vessels, 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.

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 level 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.

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. The United States also argues that, in any event,
the evidence on the record contradicts the Panel's "common-sense" approach because it shows that, in the
ETP, where it is uncontested that tuna-dolphin association 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.

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 those associated with the other fishing method 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 the 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 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-flagged large purse-seine
vessels fishing in the ETP must be accompanied by these TTFs, and importers of tuna and tuna products
containing tuna caught by non-US-flagged ETP large purse-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 process. 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 products 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 fisheries, the tuna can only be
traced back to the vessel and trip on which it was 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)

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 appellant'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)

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 whether 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 that "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, and 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 labelling conditions", thus
encompassing not only the ineligibility of tuna products derived from tuna caught by setting on dolphins for
access the dolphin-safe label, but also the different certification and tracking and verification requirements.
(Ibid., paras. 7.430 and 7.492)
873 Panel Report, paras. 7.444-7.446.
875 Panel Report, para. 7.447.
876 Panel Report, para. 7.499.
877 Panel Report, para. 7.454.
879 Panel Report, para. 7.455.
880 Panel Report, para. 7.501.

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 Agreement 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

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 detriment 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.

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 Agreement 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 this 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)

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 existing 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 conditions" 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 tuna 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).

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.

Article XX.920 One of the panelists expressed a separate opinion similar to that which had been
expressed in the context of Article 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 majority's view, that the
United States had demonstrated that the different requirements as to who must make a dolphin-safe
certification are rationally connected or calibrated to the different risks facing dolphins 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 this reason alone, that the 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.

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 criteria 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.
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.

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 (referring 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 conditions 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).

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.

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 addressed 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 unjustifiable 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.
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.

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 provisions 962 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.

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
wi l l a lr e a d y h a ve b e e n te s t e d ag a in s t , a n d wi l l h a ve b e e n fou n d t o b e a li g n e d wit h , o n e o f t h e
objectives set out in Article XX. Indeed, prior findings 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 objective pursued by the Import Ban that falls within the
purview of Article XX(b), and even goes against this objective". See also Appellate Body Reports, US – Shrimp,
973 Panel Report, para. 7.558.
974 Panel Report, para. 7.558.

"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 Panel'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.

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 (quoting 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 panelist who wrote a separate opinion. (Ibid.)

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 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.
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 (referring 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.

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 concerning 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 are 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 requirements 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 distinguishes between several categories 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 large 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".

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 examined. 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 "conditions" 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, privilege, 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 requirement 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.

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 analysis 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 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 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 labelling 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).
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 (referring to Mexico's response to Panel question No. 57,
paras. 146 and 155). See also Panel Report, paras. 7.115 and 7.446.

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 distinction 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 the 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 does 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.

7.345. We are mindful that there are both similarities 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,
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 large 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 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.
1025 Panel Report, para. 7.141.

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.

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 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 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.

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 use 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 fisheries" includes non-purse-seine vessels in any fishery
and small purse-seine vessels in the ETP.
1036 We further noted that the amended tuna measure also 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 that 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.
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 level 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.

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 r e l ike l y t o in t e r a c t w i t h t u n a f is h i n g g e a r ,
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 those associated with the other fishing method 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 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 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-flagged large purse-seine vessels fishing
in the ETP must be accompanied by these TTFs, and importers of tuna or tuna products containing tuna caught
by non-US-flagged ETP large purse-seine vessels must provide the TTF numbers when submitting the required
import documents. Moreover, the TTFs or TTF numbers accompany the relevant 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 products 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 fisheries, the tuna can only be
traced back to the vessel and trip on which it was 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)

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

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.

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