WT/DS381/AB/RW/USA  
WT/DS381/AB/RW2  
 
14 December 2018  
(18-7872) Page: 1/111 
  Original: English  
 
 
UNITED  STATES  – MEASURES CONCERNI NG THE IMPORTATION, 
MARKETING AND SALE O F TUNA AND TUNA PROD UCTS  
RECOURSE TO ARTICLE  21.5 OF THE DSU BY T HE UNITED  STATES  
UNITED  STATES  – MEASURES CONCERNI NG THE IMPORTATION, 
MARKETING AND SALE O F TUNA AND TUNA PROD UCTS  
SECOND RECOURSE TO ARTICLE  21.5 OF THE DSU BY M EXICO  
AB-2017-9 
Report of the Appellate  Body 
 
 WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Table of Contents  
 
1 INTRODUCTION  ................................ ................................ ................................ .........  11 
2 ARGUMENTS OF THE PAR TICIPANTS  ................................ ................................ ..........  18 
3 ARGUMENTS OF THE THI RD PARTICIPANTS  ................................ ...............................  18 
4 ISSUES RAISED IN THI S APPEAL  ................................ ................................ ...............  18 
5 BACKGROUND AND MEASU RE AT ISSUE  ................................ ................................ ..... 18 
5.1 US participation in multilateral initiatives  ................................ ................................ ....... 19 
5.2 US domestic dolphin -safe labelling regime: the measure at issue and its evo lution over  
the course of the Tuna II dispute  ................................ ................................ .......................  20 
6 ANALYSIS OF THE APPE LLATE  BODY  ................................ ................................ ..........  25 
6.1 Article  2.1 of the TBT  Agreement  ................................ ................................ ..................  25 
6.1.1  Introduction  ................................ ................................ ................................ ............  25 
6.1.2  "Treatment no less favourable" under Article  2.1 of the TBT  Agreement  .........................  27 
6.1.2.1  Whether the Panels erred in their articulation of th e legal standard  .............................  27 
6.1.2.2  Whether the Panels erred in rejecting Mexico's argum ent concerning the relevance of  
the sustainability of tuna stock and the marine ecosystem  ................................ ....................  29 
6.1.3  What the legal standard under Article  2.1 of the TBT  Agreement entails in this dispute ..... 32 
6.1.3.1  Whether the Panels erred in failing to consider the nexus between the regulatory 
distinctions of the measure and its objectives  ................................ ................................ ...... 33 
6.1.3.1.1  Whether the Panels' calibration analysis took i nto account the accuracy of the  
dolphin -safe label in light of the objectives of the 2016 Tuna Measure  ................................ .... 33 
6.1.3.1.2  Whether the risks of label inaccuracy form part of the risks to which the 2016 Tuna 
Measure must be cali brated  ................................ ................................ ...............................  37 
6.1.3.1.3  Whether the Panels erred in referrin g to "margin of error" in their  
calibration analysis  ................................ ................................ ................................ ...........  39 
6.1.3.2  Whether the Panels erred by limiting aspects of their calibration analysis to a  
comparison of the risk profiles of different fishing methods  ................................ ...................  41 
6.1.3.3  Conclusion  ................................ ................................ ................................ ...........  47 
6.1.4  The Panels' assessment of risk profiles  ................................ ................................ ....... 47 
6.1.4.1  The Panels' findings ................................ ................................ ...............................  48 
6.1.4.2  Whether the Panels erred by failing to assess the risk profiles of indiv idual fisheries  ...... 51 
6.1.4.3  Whether the Panels erred by using the risk profile of  setting on dolphins in the ETP  
as a benchmark  ................................ ................................ ................................ ...............  53 
6.1.4.4  Whether the Panels erred by relying primarily on per set data and excluding other 
relevant factors  ................................ ................................ ................................ ...............  58 
6.1.4.4.1  Risks to dolphin populations  ................................ ................................ ................  60 
6.1.4.4.2  Absolute levels of  adverse effects  ................................ ................................ .........  63 
6.1.4.4.3  Insufficient regulatory oversight  ................................ ................................ ...........  66 
6.1.4.5  Conclusion  ................................ ................................ ................................ ...........  67 
6.1.5  The Panels' assessment of whether the 2016 Tuna Measure is calibrated to the risks to 
dolphins  ................................ ................................ ................................ ..........................  67 
6.1.5.1  Introduction  ................................ ................................ ................................ .........  67 
6.1.5.2  Eligibility criteria  ................................ ................................ ................................ ... 69 WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.1.5.3  Certification requirements  ................................ ................................ ......................  72 
6.1.5.4  Tracking and verification requirements  ................................ ................................ .... 81 
6.1.5.4.1  Summary of the findings from the first c ompliance proceedings regarding  
tracking and verification requirements under the 2013 Tuna Measure  ................................ ..... 81 
6.1.5.4.2  Summary of the Panels' findings regarding trackin g and verification requirements  
under the 2016 Tuna Measure  ................................ ................................ ...........................  83 
6.1.5.4.3  Legal analysis  ................................ ................................ ................................ .... 85 
6.1.5.4.4  Conclusion for tracking and verification requirements  ................................ .............  91 
6.1.5.5  The 2016 Tuna Measure "a s a whole"  ................................ ................................ ...... 91 
6.1.6  Conclusion under Article  2.1 of the TBT  Agreement  ................................ ......................  93 
6.2 Article  XX of the GATT  1994 ................................ ................................ .........................  93 
6.2.1  The Panels' findings  ................................ ................................ ................................ . 93 
6.2.2 Whether the Panels erred in finding that the 2016 Tuna Measure complies with the 
requirements of the chapeau  of Article  XX of the GATT  1994 ................................ .................  94 
6.2.3  Conclusion  ................................ ................................ ................................ ............  101 
6.3 The Panels' decision to hold a partially open meeting  ................................ ....................  102 
6.3.1  Procedural background  ................................ ................................ ...........................  102 
6.3.2  Sufficiency of Mexico's Notice of Appeal  ................................ ................................ .... 103 
6.3.3  Whether the Appellate  Body should rule on this issue  ................................ .................  107 
7 FINDINGS AND CONCLUS IONS  ................................ ................................ .................  108  
7.1 Whether the Panels erred in their findings under Article  2.1 of the TBT  Agreement  ...........  108 
7.2 Whether the Panels erred in their findings under Article  XX of the GATT  1994 ..................  110 
7.3 The Panels' decision to hold a partially open meeting  ................................ ....................  111 
7.4 Recommendation  ................................ ................................ ................................ ...... 111 
 
 
  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  ABBREVIATIONS USED I N THIS REPORT  
Abbreviation  Description  
2013 Rule  USDOC, 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  
2013 Tuna Measure  DPCIA ; United States  Code of Federal Regulations , Title 50, Part  216, 
Subpart  H (Dolphin Safe Tuna Labeling), as amended by the 2013  Rule; and 
the Hogarth  ruling  
2016 implementing 
regulations  United States  Code of Federal Regulations , Title 50, Part 216, Subpart  H 
(Dolphin Safe Tuna Labeling), as amende d by the 2013 Rule and the 
2016 Rule 
2016 Rule  Enhanced Document Requirements and Captain Training Requirements to 
Support Use of the Dolphin Safe Label on Tuna Products, United States Federal 
Register , Vol. 81, No. 56 (23 March  2016)  
2016 Tuna Measure  DPCIA ; the 2016  implementing regulations ; and the Hogarth  ruling  
AIDCP  Agreement on the International Dolphin Conservation Program  
Assistant Administrator  United States Assistant Administrator for Fisheries, N MFS, NOAA , or his/her 
designee  
Captain Training Course  NMFS  Tuna Tracking and Verification Program dolphin -safe training course  
CC catch certificate  
CDS catch documentation scheme  
CFR United States Code of Federal Regulations  
DML dolphin mortality limit 
DPCIA  Dolphin Protection Consumer Information Act of 1990, codified in 
United  States  Code, Title 16, Section 1385  
DSB Dispute Settlement  Body 
DSU Understanding on Rules and Procedures Governing the Settlement of Disputes  
ETAO  Eastern Tropical Atlantic Ocean  
ETP Eastern Tropical Pacific  
FAD fish aggregating device  
FAO Food and Agricultural Organization of the United Nations  
First Compliance Panel 
Report  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 , WT/DS381/RW , Add.1 and Corr.1  
GATT  1994 General Agreement on Tariffs and Trade 1994  
Hogarth  ruling  United  States  Court of Appeals for the Ninth Circuit, Earth Island Institute v. 
Hogarth , 494 F.3d  757 (9th Cir. 2007) ; United  States  Court of Appeals for the 
Ninth Circuit, Earth Island Institute v. Hogarth , 494 F.3d 1123 (9th Cir. 2007)  
IATTC  Inter-American Tropical Tuna Commission  
IDCP International Dolphin Conservation Program  
IDCPA  International Dolphin Conservation Program Act  
ISSF International Seafood Sustainability Foundation  
IUU illegal, unreported , and unregulated  
Mexico's panel r equest  Request for the Establishment of a Panel by Mexico  pursuant to Article  21.5 of 
the DSU , WT/DS381/ 38 
NMFS  National Marine Fisheries Service  
NOAA  National Oceanic and Atmospheric Administration  
Original Panel Report  Panel Report, United  States – Measures Concerning the Importation, Marketing 
and Sale of Tuna and Tuna Products , WT/DS381/R  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Abbreviation  Description  
Original Tuna Measure  DPCIA; United  States  Code of Federal Regulations , Title 50 , Sections  216.91 
and 216.92  (Dolphin Safe Tuna Labeling), as of 13  September 2004; and the 
Hogarth  ruling  
Panel Reports  Panel Reports, United  States – Measures Concerning the  Importation, 
Marketing and Sale of Tuna and Tuna Products – Recourse to Article  21.5 of 
the DSU by the United  States , WT/DS381/RW/USA  and Add.1 / 
United  States  – Measures Concerning the Importation, Marketing and Sale of 
Tuna and Tuna Products – Second Re course to Article 21.5 of the DSU by 
Mexico , WT/DS381/RW2  and Add.1  
PBR Potential Biological Removal  
RFMO  Regional Fishery Management Organization  
TBT Agreement  Agreement on Technical Barriers to Trade  
TTF Tuna Tracking Form  
United States' panel r equest  Request for the Establishment of a Panel by the United States  pursuant to 
Article  21.5 of the DSU , WT/DS381/ 32 
USDOC  United  States  Department of Commerce  
WCPO  Western and Central Pacific Ocean  
Working Procedures  Working Procedures for Appellate Review, WT/AB/WP/6, 16  August 2010  
WTO World Trade Organization  
WTO Agreement  Marrakesh Agreement Establishing the World Trade Organization  
PANEL EXHIBITS CITED  IN THIS REPORT  
Exhibit Number  Short Title  
(if applicable)  Description  
Original Panel Record  
Original Panel Exhibit 
MEX-11 AIDCP  Agreement on the International Dolphin Conservation 
Progr am (Annexes  I, IV(I)(3)(c), and  VII(6))  
Original Panel Exhibit 
MEX-29  United States District Court for the Northern District of 
California,  Earth Island Institute et al. v. Donald Evans et 
al., 34 ELR 20069 (N.D. Cal. 2004)  
Original Panel Exhibit 
MEX-30  United States Court of Appeals for the Ninth Circuit, Earth 
Island Institute et al. v. William T.  Hogarth , 484 F.3d 1123 
(9th Cir. 2007)  
Original Panel Exhibit 
MEX-31  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-55  AIDCP, Resolution to Adopt the Modified System for 
Tracking and Verification of Tuna (20  June 2001)   
Original Panel Exhibit US -5 DPCIA  Dolphin Protection Consumer Information Act of 1990, 
codified  in United States Code , Title 16, Section 1385  
Original Panel Exhibit US -6  United States Code of Federal Regulations , Title 50, 
Sections 216.91 and 216.92  
Original Panel Exhibit 
US-58  United  States Code of Federal Regulations , Title  50, 
Sections  216.9 1-216.9 5 
First Compliance Panel Record  
First Compliance Panel 
Exhibit MEX -7 2013 Rule  USDOC, 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  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Exhibit Number  Short Title  
(if applicable)  Description  
First Compliance Panel 
Exhibit MEX -8 DPCIA  Dolphin Protection Consumer I nformation Act of 1990, 
codified  in United States Code , Title 16, Section 1385  
First Compliance Panel 
Exhibit MEX -20  United  States Code of Federal Regulations , Title 50, 
Section  216 
First Compliance Panel 
Exhibit MEX -30  AIDCP, as amended October 2009, Article I:8 and Annex  II, 
paras.  1-3 
First Compliance Panel 
Exhibit MEX -36  AIDCP, Resolution to Adopt the Modified System for 
Tracking and Verification of Tuna (20  June 2001)   
First Compliance Panel 
Exhibit US -2 2013 
implementing 
regulations  USDOC, NMFS/NOAA, Dolphin  Safe Tuna Labeling,  United 
States Code of Federal Regulations , Title  50, Part  216, 
Subpart  H (Sections  216.90 -216.95)  
First Compliance Panel 
Exhibit US -113  Determination of Observer Programs as Qualified and 
Authorized by the As sistant Administrator for Fisheries, 
United States Federal Register , Vol. 79, No. 134 (14 July 
2014), pp. 40718 -40720  
First Compliance Panel 
Exhibit US -114  NMFS, National Observer Program FY 2012 Annual Report  
(2013)  
Panel Record in these Compliance Proceedings  
Panel Exhibit MEX -1 DPCIA  Dolphin Protection Consumer Information Act of 1990, 
codified  in United States Code , Title 16, Section 1385  
Panel Exhibit MEX -2 2016 
implementing 
regulations  USDOC, NMFS/NOAA, Dolphin  Safe Tuna Labeling,  
United  States Code of Federal Regulations, Title 50, 
Part 216, Subpart  H, Sections  216.90 -216.95  
Panel Exhibit MEX -3 Hogarth  ruling  United States Court of Appeals for the Ninth Circuit, Earth 
Island Institute et al. v. William T.  Hogarth , 484 F.3d 1123 
(9th Cir.  2007) and 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)  
Panel Exhibit MEX -8  AIDCP, Report on the International Dolphin Conservation 
Program , Doc.  MOP-28-05, 18  October 2013  
Panel Exhibit MEX -15  Food and Agricult ural Organization of the United  Nations , 
"Tuna Drifting Gillnet", 
http://www.fao.org/fisher y/fishtech/1011/en, accessed 
17 March 2014  
Panel Exhibit MEX -18  Natural Resources Defense Council, Net Loss: The  Killing of 
Marine Mammals in Foreign Fisheries  (New York, January 
2014)  
Panel Exhibit MEX -26  Food and Agricult ural Organization of the United  Nations, 
"Industrial Tuna Longlining", 
http://www.fao.org/fisher y/fishtech/1010/en, accessed 
17 March 2014  
Panel Exhibit MEX -37  Food and Agricult ural Organization of the United  Nations, 
"Trawl Nets", http://www.fao.org/fishery/geartype/103/en, 
accessed 23 March 2014  
Panel Exhibit MEX -38  Food and Agricult ural Organization of the United  Nations, 
"Tuna Handlining,"  
http://www.fao.org/fishe ry/fishtech/1012/en, accessed 
5 September 2016  
Panel Exhibit MEX -47  Enhanced Document Requirements and Captain Training 
Requirements to Support Use of the Dolphin Safe Label on 
Tuna Products, United States Federal Register , Vol. 81, 
No. 56 (23  March  2016), pp.  15444 -15449  
Panel Exhibit MEX -104  National Oceanic and Atmospheric Administration, 2015 
NOAA Marine Debris Program Report, Impact of "Ghost 
Fishing" via Derelict Fishing Gear  (Charleston, March 2015)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Exhibit Number  Short Title  
(if applicable)  Description  
Panel Exhibit MEX -127  ISSF, RFMO  Catch Documentation Schemes: A  Summary  
(Washington , DC, 14  September 2016)  
Panel Exhibit USA -1 DPCIA  Dolphin Protection Consumer Information Act of 1990, 
codified  in United States Code , Title 16, Section 1385  
Panel Exhibit USA -2 2016 
implementing 
regulations  USDOC, NMFS/NOAA, Dolphin  Safe Tuna Labeling,  United 
States Code of Federal Regulations , Title 50, Part  216, 
Subpart  H, Sections  216.90 -216.95  
Panel Exhibit USA -3  Taking and Related Acts Incidental to Commercial Fishing 
Operation s by Tuna Purse Seine Vessels in the Eastern 
Tropical Pacific Ocean,  United  States Code of Federal 
Regulations , Title 50, Section  216.24 (2016)  
Panel Exhibit USA -4 NOAA Form 370  NOAA, Form 370: Fisheries Certificate of Origin (2016)  
Panel Exhibit USA -12  T. Gerrodette , "The Tuna -Dolphin Issue", in Perrin, Wursig, 
and Thewissen (eds.), Encyclopedia of Marine Mammals , 
2nd edn (Elsevier, 2009), pp.  1192-1195 
Panel Exhibit USA -15  AIDCP, Report on the Internation al Dolphin Conservation 
Program , Doc.  MOP-32-05, 20 October 2015  
Panel Exhibit USA -60  Food and Agriculture Organization of the United Nations,  
FAO Fisheries and Aquaculture Technical Paper 5 68, 
Bycatch and Non -Tuna Catch in the Tropical Purse Seine 
Fisheries of the World  (Rome, 2013)  
Panel Exhibit USA-90  International  Dolphin Conservation Program, System for 
Tracking and Verifying Tuna, as amended (2015)  
Panel Exhibit USA -111  Dolphin Mortalities Per Set Due to ETP Dolphin Sets and in 
Other Fisheries  
Panel Exhibit USA -166  United  States Code , Title 18, Section 545  
Panel Exhibit USA -167  United  States Code , Title 18, Section 3571  
Panel Exhibit USA -169  United  States Code , Title 16, Section 3372  
Panel Exhibit USA -170  Civil Monetary Penalty Adjustments for Inflation, 
United  States Federal Register , Vol. 81, No. 109 
(7 June 2016) , pp. 36454 -36458  
Panel Exhibit USA -171  United  States Code , Title 16, Section 3373  
Panel Exhibit  USA-172  United  States Code , Title 16, Section 3374  
Panel Exhibit USA -173  United  States Code , Title 18,  Section 1001  
Panel Exhibit USA -174  United  States Code , Title 16, Section  1375 
CASES CITED IN THIS REPORT  
Short Title  Full Case Title and Citation  
Argentina – Footwear (EC)  Appellate  Body Report, Argentina – Safeguard Measures on Imports of 
Footwear , WT/DS121/AB/R , adopted 12  January  2000, DSR 2000:I, p. 515  
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 – Wheat Exports and 
Grain Imports  Appellate  Body Report, Canada – Measures Relating to Exports of Wheat and 
Treatment o f Imported Grain , WT/DS276/AB/R , adopted 27  September  2004, 
DSR 2004:VI, p. 2739  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Short Title  Full Case Title and Citation  
China – HP-SSST (EU)  Appellate  Body Report, China – Measures Imposing Anti -Dumping Duties on 
High-Performance Stainless Steel Seamless Tubes ("HP -SSST") from the 
European  Union , WT/DS460/AB/R  and Add.1, adopted 28  October  2015, 
DSR 2015:IX, p. 4573  
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, DSR 2014:III, p. 805  
Colombia – Textiles  Appellate  Body Report, Colombia – Measures Relating to the Importation of 
Textiles, Apparel and Footwear , WT/DS461/AB/R  and Add.1, adopted 
22 June 2016, DSR 2016:III, p. 1131  
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  
(Article  21.5 – Ecuador  II) /  
EC – Bananas III  
(Article  21.5 – US) Appellate  Body Reports, European Communities – Regime for the Importation, 
Sale and Distribution of Bananas – Second Recourse to Article  21.5 of the DSU 
by Ecuador , WT/DS27/AB/RW2/ECU , adopted 11  December  2008, and Corr.1 / 
European Communities – Regime fo r the Importation, Sale and Distribution of 
Bananas – Recourse to Article  21.5 of the DSU by the United  States , 
WT/DS27/AB/RW/USA  and Corr.1, adopted 22  December  2008, 
DSR 2008:XVIII, p.  7165 
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 
EC – Fasteners (China)  Appellate  Body Report, European Co mmunities – 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 – 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, DSR 2014:I, p. 7  
EC – Selected Customs 
Matters  Appellate  Body Report, European Communi ties – Selected Customs Matters , 
WT/DS315/AB/R , adopted 11  December  2006, DSR 2006:IX, p. 3791  
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 
(Article 21.5 – US) Appellate  Body Report, European Communities and Certain Member States – 
Measures Affecting Trade in Large Civil Aircraft  – Recourse to Article 21.5 of 
the DSU by the United  States , WT/DS316/AB/RW  and Add.1, adopted 
28 May 2018 
EU – Biodiesel (Argentina)  Appellate  Body Report, European  Union  – Anti-Dumping Measures on Biodiesel 
from Argentina , WT/DS473/AB/R  and Add.1, adopted 26  October  2016, DSR 
2016:VI, p. 2871  
EU – Fatty Alcohols 
(Indonesia)  Appellate  Body Report, European  Union  – Anti-Dumping Measures on Imports 
of Certain Fatty Alcohols from Indonesia , WT/DS442/AB/R  and Add.1, adopted 
29 September  2017 
EU – PET (Pakistan)  Appellate  Body Report, European  Union  – Countervailing Measures on Certain 
Polyethylene Terephthalate from Pakistan , WT/DS486/AB/R  and Add.1, 
adopted 28  May 2018 
India – Patents (US)  Appellate  Body Report, India – Patent Protection for Pharmaceutical and 
Agricultural Chemical Products , WT/DS50/AB/R , adopted 16  January  1998, 
DSR 1998:I, p. 9  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Short Title  Full Case Title and Citation  
Indonesia – Iron or Steel 
Products  Appellate  Body Report, Indonesia – Safeguard on Certain Iron or Steel 
Products , WT/DS490/AB/R , WT/DS496/AB/R , and Add.1, adopted 
27 August  2018 
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  
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  
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  
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 – 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 (Article 21.5 – 
Canada and Mexico)  Appellate  Body Reports, United  States – Certain Country of Orig in 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, 
DSR 2015:IV, p. 1725  
US – Countervailing 
Measures on Certain EC 
Products  Appellate  Body Report, United  State s – Countervailing Measures Concerning 
Certain Products from the European Communities , WT/DS212/AB/R , adopted 
8 January  2003, DSR 2003:I, p. 5  
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 (and 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 – Lead and Bismuth II  Appella te Body Report, United  States – Imposition of Countervailing Duties on 
Certain Hot -Rolled Lead and Bismuth Carbon Steel Products Originating in the 
United Kingdom , WT/DS138/AB/R , adopted 7  June 2000, DSR 2000:V, p. 2595  
US – Offset Act (Byrd 
Amendment)  Appellate  Body Report, United  States – Continued Dumping and Subsidy Offset 
Act of 2000 , WT/DS217/AB/R , WT/DS234/AB/R , adopted 27  January  2003, 
DSR 2003:I, p. 375  
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 – Shrimp  Appellate  Body Report, United  States – Import Prohibition of Certain Shrimp 
and Shrimp Products , WT/DS 58/AB/R , adopted 6  November  1998, DSR 
1998:VII, p. 2755  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Short Title  Full Case Title and Citation  
US – Steel Safeguards  Appellate  Body Report, United  States – Definitive Safeguard Measures on 
Imports of Certain Steel Products , WT/DS248/AB/R , WT/DS249/AB/R , 
WT/DS251/AB/R , WT/DS252/AB/R , WT/DS253/AB/R , WT/DS254/AB/R , 
WT/DS258/AB/R , WT/DS259/AB/R , adopted 10  December  2003, 
DSR 2003:VII, p. 3117  
US – Tax Incentives  Panel Report, United  States – Conditional Tax Incentives for Large Civil 
Aircraft , WT/DS487/R  and Add.1, adopted 22  September  2017, as modified by 
Appellate  Body Report WT/DS487/AB/R  
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 , adopte d 
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 – Tuna II (Mexico) 
(Article 21.5 – Mexico)  Appellate  Body 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 , WT/DS381/AB/RW  and Add.1, adopted 3  December  2015, 
DSR 2015:X, p. 5133  
US – Tuna II (Mexico) 
(Article 21.5 – Mexico)  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 , WT/DS381/RW , Add.1 and Corr.1, adopted 3  December  2015, as 
modified by Appellate  Body Report WT/DS381/AB/RW, DSR 2015:X, p. 5409 
and DSR 2015:XI, p. 5653  
US – Tuna II (Mexico) 
(Article  21.5 – US) /  
US – Tuna II (Mexico) 
(Article  21.5 – Mexico II)  Panel Reports, United  States – Measures Concerning the Importation, 
Marketing and Sale of Tuna and Tuna Products – Recourse to Article 21.5 of 
the DSU by the United  States , WT/DS381/RW/USA  and Add.1 / 
United  States  – Measures Concerning the Importation, Ma rketing and Sale of 
Tuna and Tuna Products – Second Recourse to Article 21.5 of the DSU by 
Mexico , WT/DS381/RW2  and Add.1, circulated to WTO Members 
26 October  2017 
US – Tuna II (Mexico) 
(Article 22.6 – US) Decision by the Arbitrator, United  States – Measures Concerning the 
Importation, Marketing and Sale of Tuna and Tuna Products – Recourse to 
Article 22.6 of the DSU by the United  States , WT/DS381/ARB , 25 April 2017 
US – Upland Cotton  Appellate  Body Report, United  States – Subsidies on Upland Cotton , 
WT/DS267/AB/R , adopted 21  March  2005, DSR 2005:I, p. 3  
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. 32 3 
US – Zeroing (Japan)  Appellate  Body Report, United  States – Measures Relating to Zeroing and 
Sunset Reviews , WT/DS322/AB/R , adopted 23  January  2007, DSR 2007:I, p. 3  
 WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  WORLD TRADE ORGANIZATION  
APPELLATE  BODY 
 
 
United  States  – Measures Concerning the 
Importation, Marketing and Sale of Tuna 
and Tuna Products  
 
Recourse to Article  21.5 of the DSU by the 
United  States  
 
United  States  – Measures Concerning the 
Importation, Marketing and Sale of Tuna 
and Tuna Products  
 
Second Recourse to Article  21.5 of the DSU by 
Mexico  
 
Mexico, Appellant  
United  States , Appell ee 
 
Australia, Third Participant  
Brazil, Third Participant  
Canada, Third Participant  
China, Third Participant  
Ecuador, Third Participant  
European  Union , Third Participant  
Guatemala, Third Participant  
India, Third Participant  
Japan, Third Participant  
Korea, Third Participant  
New Zealand,  Third Participant  
Norway,  Third Participant  AB-2017-9 
 
Appellate  Body Division:  
 
Bhatia, Presiding Member  
Graham, Member  
Zhao,  Member  
 
 
 
1  INTRODUCTION  
1.1.  Mexico appeals certain issues of law and legal interpretations developed by the Panels in 
United  States  – Measures Concerning the Importation, Marketing and Sale of Tuna and Tuna 
Products – Recourse to Article  21.5 of the DSU by the United  States  and United  States  – Measures 
Concerning the Importation, Marketing and Sale of Tuna and Tuna Products – Second Recourse to 
Article  21.5 of the DSU by Mexico .1 The Panels were established pursuant to Article  21.5 of the 
Understanding on Rules and Procedures Governing the Settlement of Disputes (DSU) to consider the 
claims by the United  States2 and Mexico3 concerning the measure taken by the United  States  to 
comply with the recommendations and rulings of the Dispute Settlement  Body (DSB) in the original 
proceedings4 and first compliance proceedings5 in this dispute.6  
                                                
1 WT/DS381/R W/USA; WT/DS381/RW2, 26  October  2017. The Panels explained that they decided to 
issue their findings in a single document, with separate conclusions for each of the two proceedings. We refer 
to both Reports collectively as the "Panel Reports". (See Panel Reports, para.  7.4) 
2 Request for the E stablishment of a Panel by the United  States pursuant to Article  21.5 of the DSU, 
WT/DS381/32 (United States' panel request).  
3 Request for the Establishment of a Panel by Mexico pursuant to Article  21.5 of the DSU, WT/DS381/38 
(Mexico's panel request).  
4 The recommendations and rulings of the DSB resulted from the adoption by the DSB, on 
13 June 2012, of the Appellate  Body report (WT/DS381/AB/R) and the panel report (WT/DS381/R) in  
US – Tuna II (Mexico) . 
5 The recommendations and rulings of the DSB result ed from the adoption by the DSB, on  3 December 
2015, of the Appellate  Body report (WT/DS381/AB/RW) and the panel report (WT/DS381/RW) in US – Tuna II 
(Mexico) (Article  21.5 – Mexico) . 
6 In this Report, we refer to the panel that considered the original com plaint brought by Mexico as the 
"original panel" and to its report as the "original panel report". We refer to the panel that considered Mexico's WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  1.2.  This dispute concerns the United  States ' labelling 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 Technical Barriers to Trade ( TBT Agreement ) challenging the 
consistency with these Agreements of certain US measures relating to  the importation, marketing, 
and sale of tuna and tuna products.7 Specifically, Mexico challenged: (i) the Dolphin Protection 
Consumer Information Act of 1990, codified in United  States  Code, Title 16, Section 13858 (DPCIA); 
(ii) United  States  Code of Federal Regulations (CFR), Title 50, Sections 216.91 and  216.929 (original 
implementing regulations); and (iii) a ruling by a U nited States  Federal Appeals Court in Earth Island 
Institute v. Hogarth10 (Hogarth  ruling).11 The original panel and the Appe llate Body referred to these 
measures, collectively, as the "measu re at issue" or the "US  dolphin -safe labelling provisions".12 
In these compliance proceedings, we refer to them as the "original Tuna Measure".  
1.3.  The original Tuna Measure specified the conditi ons 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.13 The 
original Tuna Measure thus prohibit ed the use of the "dolphin -safe" label on a tuna product sold in 
the US market unless the conditions specified in the measure are met. At the same time, it did not 
make the use of a dolphin -safe label obligatory for the importation or sale of tuna products i n the 
United  States .14 Nonetheless, the preferences of retailers and cons umers 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.15  
1.4.  Mexico alleged that the original Tuna Measure was inconsistent with Articles I:1 and  III:4 of 
the GATT  1994 and Articles 2.1, 2.2, and 2.4 of the TBT Agreement .16 The original panel found that: 
(i) the US "dolphin -safe" labelling provisions constituted a "t echnical regulation" within the meaning 
of Annex 1.1 to the TBT Agreement17; (ii) the measure was not inconsistent with Article  2.1 of the 
TBT Agreement18; (iii) the measure was inconsistent with Article  2.2 of the TBT Agreement19; and 
(iv) the Agreement on t he International Dolphin Conservation Program20 (AIDCP) dolphin -safe 
definition and certification were a relevant international standard  within the meaning of Article 2.4 
of the TBT Agreement21, and the measure was not inconsistent with that provision .22 The original 
                                                
complaint in the first compliance proceedings as the "first compliance panel" and to its report as the "first 
compliance panel report".  
7 In 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 ori ginal panel limited its findings in this respect to tuna products. (Original Panel Report, 
para. 6.10)  
8 Original Panel Exhibit US -5. 
9 Original Panel Exhibit US -6 and US -58. 
10 Earth Island Institute v. Hogarth , 494 F.3d 757 (9th Cir. 2007) (Original Panel  Exhibit MEX -31); Earth 
Island Institute v. Hogarth , 484 F.3d 1123 (9th Cir. 2007) (Original Panel Exhibit MEX -30). See infra, fn 104.  
11 Original Panel Report, para.  2.1. 
12 The original panel and the Appellate  Body considered it appropriate to treat these  legal instruments 
as a single measure for the purpose of analysing Mexico's claims and reaching findings. (Original Panel Report, 
para. 7.26. See also Appellate  Body Report, US – Tuna II (Mexico) , paras.  2 and 172 and fn  357 thereto)  
13 Appellate  Body Repo rt, US – Tuna II (Mexico) , para.  172. The original panel found that the DPCIA 
defines "tuna product" 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". (Original Panel 
Report, paras.  2.5 and 7.60 (quoting DPCIA (Original Panel Exhibit US -5), Section  1385(c)(5)) See also 
Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , fn 101 to para.  6.1) 
14 Appellate  Body Report , US – Tuna II (Mexico) , paras.  172 and 196 -199. 
15 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 
paragrap hs 2.1-2.41 of the original panel report, and paragraphs 172 -177 of the Appellate  Body report in the 
original proceedings.  
16 Original Panel Report, para. 3.1.  
17 Original Panel Report, paras.  7.62, 7.78, and 7.145. This finding was upheld on appeal. (See 
Appellate  Body Report, US – Tuna II (Mexico) , para.  199) 
18 Original Panel Report, paras.  7.374 and 8.1(a).  
19 Original Panel Report, paras.  7.620 and 8.1(b).  
20 Original Panel Exhibit MEX -11. 
21 Original Panel Report, para.  7.707. (Both Mexico and the United  States are parties to the AIDCP, an 
agreement among 14 countries that entered into force in February 1999. (Original Panel Report, para.  2.35) 
The AIDCP, administered by the Inter -American Tr opical Tuna Commission (IATTC), addresses a particular 
tuna-fishing method (purse seine fishing) in a specific area of the ocean, namely, the Eastern Tropical Pacific 
(ETP). (Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  6.4)) 
22 Original Panel Report, paras.  7.740 and 8.1(c).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  panel exercised 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 reversed the original panel's finding under Article  2.1 of the 
TBT Agreement . The Appellate  Body found, instead, that the United  States  had not demonstrated 
that the detrimental impact of the measure on Mexican tuna products stemmed exclusively from a 
legitimate regulatory distinction. The Appellate  Body thus concluded that the original Tuna Measure 
accorded less favourable treatment to Mexican tuna products than that accorded to like products 
from the United  States  and other countries, and it was inconsistent with Article  2.1 of the 
TBT Agreement .24 Furthermore, the Appellate  Body found that the panel  had erred in concluding 
that the original Tuna Measure was more trade restrictive than necessary to fulfil the United  States ' 
legitimate objectives, taking into account the risks non -fulfilment would create, and therefore 
reversed the finding of inconsist ency under Article  2.2 of the TBT Agreement .25 The Appellate  Body 
also reversed the original panel's finding that the AIDCP dolphin -safe definition and certification 
constituted a relevant international standard, but left undisturbed the panel's finding tha t the original 
Tuna Measure was not inconsistent with Article  2.4 of the TBT Agreement .26 Finally, the 
Appellate  Body found that the original panel acted inconsistently with Article  11 of the DSU in 
deciding to exercise judicial economy with respect to Mexi co's claims under Articles  I:1 and III:4 of 
the GATT  1994.27 In conclusion, the Appellate  Body recommended that the DSB request the 
United  States  to bring its measure into conformity with its obligations under the TBT Agreement .28 
1.6.  On 13  June 2012, the DSB ad opted the original panel and Appellate  Body reports.29 
On 17 September  2012, Mexico and the United  States  informed the DSB that they had agreed on a 
reasonable period of time – 13 months from 13  June 2012 – to comply with the recommendations 
and rulings of the DSB . The reasonable period of time expired on 13  July 2013.30 
1.7.  On 9 July 2013, the United  States  published amendments to Sections 216.91 and  216.93 of 
CFR Title 5031 (2013 Rule) .32 According to the United  States , the 2013 Rule constituted the measure 
taken  to comply with the recommendations and rulings of the DSB pursuant to Article  21.5 of the 
DSU.33  
1.8.  Mexico considered that the United  States  had not brought its labelling regime into compliance 
with the recommendations and rulings of the DSB, and that the re gime remained inconsistent with 
its obligations under the covered agreements.34 On 2 August 2013, Mexico and the United  States  
                                                
23 Original Panel Report, paras.  7.748 and 8.2.  
24 Appellate  Body Report, US – Tuna II (Mexico) , paras.  298-299 and 407(b).  
25 Appellate  Body Report, US – Tuna II (Mexico) , paras.  331 and 407(c).  
26 Appellate  Body Report, US – Tuna II (Mexico) , paras.  401 and 407(f).  
27 Appellate  Body Report, US – Tuna II (Mexico) , paras.  405 and 407(g).  
28 Appellate  Body Report, US – Tuna II (Mexico) , para.  408. 
29 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. (First Compliance 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))  
30 First Compliance Panel Report, para.  1.12 (referring to Agreement under Article  21.3(b) of the DSU, 
WT/DS381/17).  
31 United States  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 (First Compliance Panel 
Exhibit MEX -7). Section 216.92 of the original implementing regulations, the DPCIA, and the Hogarth  ruling 
remained unchanged. (First Compliance Panel  Report, paras.  3.32 and 3.39)  
32 First Compliance Panel Report, para.  1.13 (referring to United  States' first written submission to the 
first compliance panel, para.  10). We note that the first compliance panel referred to these amendments as the 
"2013 Final Rule", whereas the Panels referred to them as the "2013 Rule". (Fir st Compliance Panel Report, 
paras.  1.13 and 2.1; Panel Reports, para.  2.1) For the purpose of this Report, we refer to them as the 
"2013  Rule".  
33 First Compliance Panel Report, para.  1.13. 
34 First Compliance Panel Report, para.  1.14. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  informed the DSB of their Agreed Procedures under Articles  21 and 22 of the DSU .35 
On 14 November  2013, Mexico requested the establ ishment of a panel under Articles  6 and 21.5 of 
the DSU, Article  14 of the TBT Agreement , and Article  XXIII of the GATT  1994.36 In its panel requ est, 
Mexico indicated that the measure taken to comply with the recommendations and rulings of the 
DSB (2013 Tun a Measure) comprised: (i) the DPCIA; (ii)  Subpart H of Part 216 of CFR  Title 50 as  
amended by the 2013 Rule (2013  implementing regulations)37; (iii) the Hogarth  ruling38; 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.39 Mexico claimed that the 2013 Tuna Measure was inconsistent with Article  2.1 
of the TBT Agreement , Article  I:1 of the GATT  1994, and Article  III of the GATT  1994.40  
1.9.  The first compliance panel considered that the question before it was whether the 2013 Tuna 
Measure brought the United  States  into compliance with the covered agreements .41 The first 
compliance panel found that : (i) the eligibility criteria were consistent with Article  2.1 of the 
TBT Agreement42, but inconsistent with Articles I:1 and  III:4 of the GATT  199443; (ii) the certification 
requirements and the tracking and verification requirements were inconsistent with  Article  2.1 of the 
TBT Agreement  and Articles I:1 and III:4 of the GATT  199444; (iii) the eligibility criteria, certification 
requirements, and tracking and verification requirements under the 2013 Tuna Measure were 
provisionally justified under Article  XX(g) of the GATT  199445; and (iv)  the eligibility criteria met the 
requirements of the chapeau  of Article  XX, whereas the certification requirements and the tracking 
and verification requirements constituted arbitrary or unjustifiable discrimination, and accordingly 
did not satisfy the requirements of the  chapeau  of Article  XX of the GATT  1994.46  
1.10.   On appeal,  the Appellate  Body reversed the first compliance panel's findings under Article  2.1 
of the TBT Agreement , Articles I:1 and III:4 of the GATT  1994, and the chapeau  of Article  XX of the 
GATT  1994.47 In particular, the Appellate  Body considered that the first co mpliance panel had 
conducted isolated analyses of, and reached separate findings with respect to, each of the three 
components of the 2013 Tuna Measure, without accounting for the manner in which these elements 
were interrelated.48 The Appellate  Body also found that the first compliance panel erred by failing to 
consider whether the differences in the relevant labelling conditions under the measure were 
                                                
35 First Compliance Pan el Report, para. 1.15 (referring to WT/DS381/19). The parties agreed that, in the 
event that the DSB, following a proceeding under Article  21.5 of the DSU, ruled 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 would not assert that Mexico is precluded from 
obtaining such authorization on the grounds that the request was made outside the 30 -day time period 
specified in Article  22.6 of the DSU. (WT/DS381/19, para. 5)  
36 First Compliance Panel Report, para. 1.1 (referring to WT/DS381/20). See also Appellate  Body 
Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  1.8. 
37 USDOC, National Marine Fisheries Service (NMFS)/NOAA, Dolphin Safe Tuna Labeling, 2013 
implementing regulations, Sections 216.90 -216.95. (First Compliance Panel  Exhibit US -2) 
38 See para. 5 .10 below and fn 104 thereto.  
39 First Compliance Panel Report, para.  2.1. 
40 First Compliance Panel Report, para.  2.2. Mexico also claimed that the 2013 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.  
41 First Compliance Panel Report, para.  7.24. The first compliance panel agreed with both parties that 
the 2013 Tuna Measure was a "technical regulation" for the purpose of the TBT  Agreement, and that the 
relevant tuna products were "like". (Ibid., para.  7.71) The first compliance panel disagreed with the 
United  States that the [2013 Rule] is "separable from the rest of the tuna measure". The first compliance panel 
instead expressed the view that the 2013 Final Rule was "an integral component" of the 2013 Tun a Measure 
and "the fact that it add[ed] new requirements rather than changing pre -existing requirements … d[id] 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 first com pliance panel's] jurisdiction." (Ibid., para.  7.41 (fn  omitted))  
42 First Compliance Panel Report, paras.  7.135 and 8.2.a.  
43 First Compliance Panel Report, paras.  7.451, 7.499, and 8.3.a.  
44 First Compliance Panel Report, paras.  7.233, 7.263, 7.400, 7.456, 7 .465, 7.501, 7.503, 8.2.b -c, 
and 8.3.b-c. 
45 First Compliance Panel Report, paras.  7.541 and 8.4.  
46 First Compliance Panel Report, paras.  7.585, 7.605, 7.611, and 8.5.  
47 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.230, 7.2 82, 7.335, 
and 8.1. 
48 See Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.14-7.21, 
7.169,  7.229, and 7.335.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  calibrated to, or explained by, differences in the relative risks of harm to dolphins from different 
fishing methods in different areas of the ocean.49  
1.11.   Having reversed the first compliance panel's findings, the Appellate  Body completed the 
analysis and found that: (i)  the 2013 Tuna Measure modified the conditions of competition to the 
detriment of Mexican tuna products in the US market; (ii)  such detrimental impact did not stem 
exclusively from a legitimate regul atory distinction; and, thus, (iii)  the 2013 Tuna Measure accorded 
less favourable treatment to Mexican tuna products compared to like tuna products from the 
United  States  and other countries.50 Therefore, the Appellate  Body found that the 2013 Tuna 
Measure  was inconsistent with Article  2.1 of the TBT Agreement . The Appellate  Body also found that 
the 2013 Tuna Measure was inconsistent with Articles  I:1 and III:4 of the GATT  1994, and that the 
United  States  had not demonstrated that the measure was applied in  a manner that did not 
constitute arbitrary or unjustifiable discrimination as required by the chapeau  of Article  XX of the 
GATT  1994.51 The Appellate  Body thus recommended that the DSB request the United  States  to 
bring its measure into conformity with its  obligations under the TBT Agreement  and the 
GATT  1994.52 
1.12.   The DSB adopted the first compliance panel report and the Appellate  Body report 
on 3 December 2015.53 On 22  March 2016, the United  States  published a new rule modifying the 
2013 Tuna Measure54 (2016 Ru le) with the aim of bringing the 2013  Tuna Measure into compliance 
with the recomme ndations and rulings of the DSB .55 Following the issuance of the 2016 Rule, the 
United  States  and Mexico each requested the establishment of a compliance panel under Article  21.5 
of the DSU.56 On 29  July 2016, the Panels in the proceedings brought by the United  States  and the 
proceedings brought by Mexico adopted a harmonized timetable for these compliance proceedings 
and thereafter held a consolidated substantive meeting with the parties on 24 and 
25 January  2017.57 
1.13.   In these compliance proceedings, the United  States  requested the Panels to find that the 
United  States  has brought itself into compliance with the recommendations and rulings of the DSB 
and that the measure taken to comply with the recommendations and rulings of the DSB  is consistent 
with Article  2.1 of the TBT Agreement  and justified under Article  XX of the GATT  1994.58 Mexico 
requested the Panels to reject the United  States ' claims in their entirety and to find that the measure 
taken to comply with the recommendations and rulings of the DSB is inconsistent with Article  2.1 of 
                                                
49 See Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.169,  7.229, 
and 7.334.  
50 Appella te Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.238, 7.266, 7.340, 
7.360, and 8.1.  
51 Panel Reports, para.  7.2 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  8.1). 
52 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  8.2. 
53 On 10  March 2016, Mexico requested authorization from the DSB to suspend concessions to the 
United  States in the amount of US$472.3 million annually (WT/DS381/29). On 25  April 2017, while the 
comp liance proceedings were pending before the Panels, the Arbitrator circulated its decision to WTO Members. 
The Arbitrator determined that the level of nullification or impairment suffered by Mexico as a result of the 
2013 Tuna Measure is US$163.23 million a nnually. The Arbitrator concluded that, in accordance with 
Article  22.4 of the DSU, Mexico may request authorization from the DSB to suspend concessions or other 
obligations up to a level not exceeding US$163.23 million annually. (Decision by the Arbitrato r, US – Tuna II 
(Mexico) (Article  22.6 – US), para.  7.1) On 11  May 2017, Mexico requested authorization from the DSB to 
suspend the application of certain tariff concessions and related obligations to the United  States under the 
GATT  1994 in the amount of US$163.23 million. (WT/DS381/44) At its meeting on 22  May 2017, the DSB 
authorized Mexico to suspend the application to the United  States of concessions or other obligations. 
(WT/DSB/M/397)  
54 Panel Reports, para. 2.3. See also Enhanced Document Requirement s and Captain Training 
Requirements to Support Use of the Dolphin Safe Label on Tuna Products, United  States Federal Register , 
Vol. 81, No. 56 (23  March  2016) (Panel Exhibit MEX -47). 
55 Panel Reports, para.  7.3. 
56 WT/DS381/32; WT/DS381/38. In addition to Article  21.5 of the DSU, Mexico's request was also made 
pursuant to Article  6 of the DSU, Article  14 of the TBT  Agreement, and Article  XXIII of the GATT  1994. (See 
WT/DS381/38. See also Panel Reports, para.  1.7) 
57 Panel Reports, paras.  1.11-1.13. 
58 Panel Reports, para.  3.1. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the TBT Agreement  and Articles I:1 and III:4 of the GATT  1994, and cannot be justified under 
Article  XX of the GATT  1994.59 
1.14.   During the P anel proc eedings, the United  States  and certain third parties60 requested the 
Panels to lift the confidentiality of their statements at the Panels' consolidated substantive meeting 
with the parties and at the third -party session.61 Mexico objected to such request, ar guing that the 
Panels could open their substantive meeting with the parties to public viewing only with the consent 
of both parties.62 The Panels, after consulting with the parties, adopted Additional Working 
Procedures on Partially Open Meetings.63 Pursuant  to the ir Additional Working Procedures, the Panels 
permitted the partial public observation of the Panels' consolidated substantive meeting with the 
parties and session with the third parties through delayed viewing, to ensure that the confidentiality 
of Mexico's statements and the statements of non -disclosing third parties was not breached.64 
1.15.   The Panel Reports were circulated to Members of the World Trade Organization ( WTO) on 
26 October  2017. The Panels identified the measure at issue in these compliance proceedings  
(2016  Tuna Measure) , as consisting of the following instruments: ( i) the DPCIA; ( ii) Subpart H of 
Part 216 of CFR Title 50 as amended by the 2013 Rule and the 20 16 Rule (collectively, the 
2016 implementing regulations); and ( iii) the Hogarth  ruling.65 The Panels noted the parties' 
agreement that: (i) the 2016 Tuna Measure is a technical regulation within the meaning of Annex 1.1 
to the TBT Agreement ; (ii) Mexican tuna products are "like" tuna products produced by the 
United  States  and other count ries; (iii)  the 2016 Tuna Measure modifies the conditions of 
competition to the detriment of Mexican tuna products in the US market under Article  2.1 of the 
TBT Agreement ; (iv) the 2016 Tuna Measure is inconsistent with both Article  I:1 and Article  III:4 o f 
the GATT  1994; and (v) the 2016 Tuna Measure is  provisionally justified under Article  XX(g) of the 
GATT  1994.66  
1.16.   The Panels considered that the parties' disagreement centred on the question whether the 
detrimental impact accords "treatment no less favourable" within the meaning of Article  2.1 of the 
TBT Agreement  because such detrimental impact stems exclusively from  a legitimate regulatory 
distinction.67 The Panels found that, to address this question, the applicable  legal standard under 
Article  2.1 of the TBT Agreement  require d them to assess whether the relevant regulatory 
distinctions under the measure at issue are  calibrated to the risks to dolphins arising from the use 
of different fishing methods in different areas of the ocean.68 On the basis of their findings regarding 
the risks to dolphins69, the Panels found that each of the elements of the 2016 Tuna Measure70 and 
the 2016 Tuna Measure as a whole are calibrated in accordance with the applicable legal standard.71 
Relying on their analysis under Article  2.1 of the TBT Agreement , the Panels found that the 
                                                
59 Panel Reports, para.  3.2. 
60 Australia, Canada, the European  Union, Japan, New Zealand, and Norway supported the 
United  States' request, while Brazil, China, Ecuador, Guatemala, India, and Korea  opposed it. (Panel Reports, 
paras.  7.14-7.15)  
61 Panel Reports, para.  1.14. 
62 Panel Reports, paras.  7.10-7.13. 
63 Panel Reports, para.  1.19. See also Annex A -4 to the Panel Reports (Panels' Additional Working 
Procedures).  
64 Panel Reports, paras.  1.20 and 7. 5-7.34. In addition, upon request by both parties, the Panels 
adopted Additional Working Procedures of the Panels Concerning Business Confidential Information. (See Panel 
Reports, paras.  1.22-1.23; Annex A -3 to the Panel Reports)  
65 Panel Reports, paras.  2.1 and 7.47. In addition to the three items referred to above, the Panels noted 
that Mexico, in its panel request in these compliance proceedings, also referred to "[a]ny implementing 
guidance, directives, policy announcements or any other document issued i n relation to instruments [(i)] 
through [(iii)] above, including any modifications or amendments in relation to those instruments". (Ibid., 
para. 7.43 (quoting Mexico's panel request, p.  2)) Having reviewed all of Mexico's submissions and evidence in 
these  compliance proceedings, the Panels observed that Mexico's description had referred to this additional 
element "in the abstract, without arguing that in fact there exists such an element which is subsumed within 
the definition of the measure taken to compl y subject to these proceedings". (Ibid., para.  7.44) Furthermore, 
the Panels considered that "the claims and arguments that Mexico has presented in these proceedings [did] not 
in any way pertain to this alleged additional element of the 2016 Tuna Measure."  (Ibid.)  
66 Panel Reports, paras.  7.74-7.75 and 7.729 -7.730.  
67 Panel Reports, para.  7.79. 
68 Panel Reports, para.  7.103.  
69 Panel Reports, section 7.7.  
70 These elements of the 2016 Tuna Measure are explained in section 5.2 below.  
71 Panel Reports, paras.  7.547, 7.611, 7.676, and 7.717.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  2016 Tuna Measure is not applied in a manner that constitutes a means of arbitrary or unjustifiable 
discrimination within the meaning of the chapeau  of Article  XX of the GATT  1994.72  
1.17.   On this basis : 
a. with respect to the United  States ' and Mexico's claims under Article  2.1 of the 
TBT Agreement , the Panels concluded that  the 2016 Tuna Measure is not inconsistent with 
Article  2.1 of the TBT Agreement73; and 
b. with respect to Mexico's claims under the GATT  1994, and the United  States'  defence 
under Article  XX of the GATT  1994, the Panels concluded that the 2016 Tuna Measure is  
inconsistent with Articles I:1 and III:4 of the GATT  199474, but is justified under 
Article  XX(g), and meets the requirements of the chapeau  of Article  XX.75 
1.18.   The Panels therefore considered that the United  States  has implemented the 
recommendations and ruli ngs of the DSB in the original and first compliance proceedings of this 
dispute to bring its measure into conformity with its obligations under the Marrakesh Agreement 
Establishing the World Trade Organization ( WTO Agreement ). Thus, th e Panels did not find  it 
necessary to make any recommendations under Article  19.1 of the DSU.76 
1.19.   On 1 December  2017, 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 Reports, and certain l egal 
interpretations developed by the Panels, and filed a Notice of Appeal and an appellant's submission.77 
On 19  December  2017, the United  States  filed an appellee's submission.78 On 4  January  2018, 
Australia, Brazil, the European  Union, and Japan each filed a third  participant's submission.79 
On 3-4 January  2018, Canada, China, Ecuador, Guatemala, India, New Zealand, and Norway each 
notified its intention to appear at the oral hearing as a third participant.80 Subsequently, Korea also 
notified its intention to appear at the oral hearing as a third  participant.81  
1.20.   By letter dated 29  January  2018, the Chair of the Appellate  Body notified the Chair of the DSB 
that the Appellate  Body would not be able to circulate i ts Report within the 60 -day period pursuant 
to Article  17.5 of the DSU, or within the 90 -day period pursuant to the same provision, for the 
reasons mentioned therein.82 For the reasons explained in the letter, work on this appeal could 
gather pace only in M ay 2018 . On 20 November 2018 , the Chair of the Appellate  Body notified the 
Chair of the DSB that the Appellate  Body Report in these proceed ings would be circulated to 
WTO Members no later than 14 December 2018 . 
1.21.   The oral hearing in this appeal was held on 3 0-31 July 2018. The participants and five of the 
third participants (Brazil, Canada, the European  Union , Japan, and Norway) made opening oral 
                                                
72 Panel Reports, para.  7.740.  
73 Panel Reports, paras.  8.2 and 8.6.  
74 Panel Reports, para. 8.7.  
75 Panel Reports, paras.  8.3 and 8.7.  
76 Panel Reports, paras.  8.4-8.5 and 8.8 -8.9. 
77 Pursuant to Rules  20 and 21, respectively, of the Working Procedures for Appellate Review, 
WT/AB/WP/6, 16  August  2010 (Working Procedures).  
78 Pursuant to Rule 22 of the Working Procedures.  
79 Pursuant to Rule 24(1) of the Working Procedures. According to the Working Schedule dra wn up by 
the Division hearing this appeal, the third participants' submissions and executive summaries were due on 
3 January  2018. On 20  December  2017, the Appellate  Body Division issued a procedural ruling extending the 
deadline to 4  January  2018 for all third participants following a request by Japan dated 19  December  2017 to 
extend the deadline. The Procedural Ruling is contained in Annex  D of the Addendum to this Report, 
WT/DS381/AB/RW/USA/Add.1; WT/DS381/AB/RW2/Add.1.  
80 Pursuant to Rule 24(2) of the Wo rking Procedures. Canada, New Zealand, and Norway each notified 
its intention on 3  January  2018, and the other third participants did so on 4  January  2018.  
81 On 27  July 2018, Korea submitted its delegation list for the oral hearing to the Appellate  Body 
Secretariat and the participants and third participants in this dispute. For the purpose of this appeal, we have 
interpreted this action as a notification expressing Korea's intention to attend the oral hearing pursuant to 
Rule 24(4) of the Working Procedure s. 
82 WT/DS381/46. The letter is contained in Annex E of the Addendum to this Report, 
WT/DS381/AB/RW/USA/Add.1; WT/DS381/AB/RW2/Add.1.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  statements. The participants and third participants responded to questions posed by the Members 
of the Appellate  Body Division hearing the appeal.  
2  ARGUMENTS OF THE PAR TICIPANTS  
2.1.  The claims and arguments of the participants are reflected in the executive summaries of their 
written submissions provided to the Appellate  Body.83 The Notice of Appeal and the executive 
summar ies of the participants' claims and arguments are contained in Annexes A and B of the 
Addendum to th is Report, WT/DS381/AB/RW/USA/Add.1, WT/DS381/AB/RW2/Add.1.  
3  ARGUMENTS OF THE THI RD PARTICIPANTS  
3.1.  The arguments of the third participants that filed a written  submission (Australia, Brazil, the 
European  Union , and Japan) are reflected in the executive summaries of their written submissions 
provided to the Appellate  Body84 and are contained in Annex C of the Addendum to th is Report, 
WT/DS381/AB/RW/USA/Add.1, WT/D S381/AB/RW2/Add.1.  
4  ISSUES RAISED IN THIS A PPEAL  
4.1.  The following issues are raised in this appeal:  
a. whether the Panels erred in finding that the 2016  Tuna Measure accords to Mexican tuna 
products treatment no less favourable than that accorded to like products originating in 
the United  States  and other countries and is therefore consistent with Article  2.1 of the 
TBT Agreement . Specifically, in determining whether the detrimental impact caused by the 
2016 Tuna Measure stems exclusively from a legitimate regulatory distinction , whether 
the Panels erred:  
i. by failing to include risks relating to inaccurate labelling in their calibratio n analysis, 
and thereby failing to assess whether the regulatory distinctions under the 2016 Tuna 
Measure are rationally related to its objectives;  
ii. by failing to properly assess the risk profiles of different fishing methods and ocean 
areas for  the purpos e of their calibration analysis; and  
iii. by finding that the individual components of the 2016  Tuna Measure (i.e. the eligibility 
criteria; the certification requirements; and the tracking and verification 
requirements), as well as the 2016  Tuna Measure as a w hole, are calibrated to the 
risks to dolphins arising from the use of different fishing methods in different ocean 
areas ; 
b. whether the Panels erred in finding that the 2016 Tuna Measure is not applied in a manner 
that constitutes "a means of arbitrary or un justifiable discrimination between countries 
where the same conditions prevail" and is therefore justified under Article  XX of the 
GATT  1994; and  
c. whether the Panels erred in finding  that they had the authority to conduct a partially open 
meeting of the parties without the consent of both parties.  
5  BACKGROUND AND MEASU RE AT ISSUE  
5.1.  These compliance proceedings represent the third time that the dispute between Mexico and 
the United  States  over the WTO -consistency of the United  States ' labelling regime for dolphin -safe 
tuna products is before us. As the Appellate  Body in the first compliance proceedings described, 
                                                
83 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).  
84 Pursuant to the Appellate  Body's communication on "Executive Summaries of Written Submissions in 
Appellate Proceedings" and "Gui delines in Respect of Executive  Summaries of Written Submissions in 
Appellate  Proceedings" (WT/AB/23, 11  March 2015).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  commercial tuna fishing can have harmful effects on marine mammals, including  dolphins, and these 
effects 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.85 As we describe 
below, the United  States  has undertaken ce rtain domestic measures, and participated in certain 
multilateral initiatives, aimed at reducing the adverse effects on dolphins associated with commercial 
fishing operations.  
5.1  US participation in multilateral initiatives  
5.2.  The United  States  and Mexico are pa rties to the A IDCP, which entered into force in 
Februar y 1999.86 The AIDCP, administered by the Inter -American Tropical Tuna Commission 
(IATTC), addresses a particular tuna -fishing method (purse seine fishing) in a specific area of the 
ocean, namely the Eas tern Tropical Pacific (ETP).87 
5.3.  As the original panel described, there is a regular association between tuna and dolphins in the 
ETP, meaning that schools of tuna tend to aggregate and swim beneath certain species of dolphins.88 
Certain vessels operating in t his area em ploy a fishing method known as setting on dolphins, which 
takes advantage of this association. This fishing method involves chasing and encircling the dolphins 
with a purse seine net in order to catch the tuna swimming beneath the m.89 The ETP is a "traditional 
fishing ground" for Mexico, and its tuna fleet operates almost exclusively therein using the method 
of setting on dolphins.90 
5.4.  As the original panel noted, the AIDCP was negotiated in response to evidence that many 
dolphins were dying in the E TP each year91 and is recognized to have made an important contribution 
to dolphin protection and to the dramatic reduction of observed dolphin mortality in the ETP.92 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), and subject to 
a number of requirements.93 
5.5.  The AIDCP es tablishes a dolphin -safe scheme for the ETP that is separate from the US  domestic 
scheme.94 Under the AIDCP, " dolphin -safe tuna" is a term that is used to describe "tuna captured in 
sets in which there is no mortality or serious injury of dolphins".95 
                                                
85 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  6.2. 
86 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. (Appellate  Body Rep ort, US – Tuna II (Mexico) (Article  21.5 – Mexico) , 
fn 106 to para.  6.4) 
87 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  6.4. 
88 Original Panel Report, para.  7.306; Appellate  Body Report, US – Tuna II (Mexico) , fn 355 to 
para. 172. 
89 Appellate  Body Report, US – Tuna II (Mexico) , fn 355 to para.  172. See also ibid., para.  248; Original 
Panel Report,  para. 7.306.  
90 Appellate  Body Report, US – Tuna II (Mexico) , para.  234. See also Original Panel Report, para.  7.308; 
Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  6.5. 
91 Original Panel Report, para.  2.35. 
92 Original Panel Report, paras.  2.39 and 7.609.  
93 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. 
(Appellate  Body Report, US – Tuna II (Mexico)  (Article  21.5 – Mexico) , para. 6.6 and fn 116 thereto (referring 
to United  States' appellant's submission in the first compliance proceedings, fn  61 to para.  65; AIDCP, 
Annexes  I, IV(I)(3)(c), and VII(6) (Original Panel Exhibit MEX -11); AIDCP, as amended October 2009, 
Article  I:8 and Annex II, paras. 1 -3 (First Compliance Panel Exhibit MEX -30))) 
94 Original Panel Report, para.  2.34. 
95 Original Panel Report, para.  2.40 (quoting AID CP, Resolution to Adopt the Modified System for 
Tracking and Verification of Tuna (20  June 2001) (Original Panel Exhibit MEX -55)). (emphasis original)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  5.2  US domestic dolphin -safe labelling regime: the measure at issue and its evolution 
over the course of the Tuna  II dispute  
5.6.  As indicated in  para. 1.15  above, the Panels described the 2016 Tuna Measure (the measure 
at issue in these compliance proceedings) as con sisting of the following three elements "on which 
both parties agree, and to which both parties ' claims and arguments pertain"96: 
a. the DPCIA;  
b. Subpart H of Part 216 of CFR Title 50 (Dolphin Safe Tuna Labeling), as amended by the 
Enhanced Document Requirements  to Support Use of the Dolphin Safe Label on Tuna 
Products, 78 Fed. Reg. 40,997 (9  July 2013) (2013 Rule) and the Enhanced Document 
Requirements and Captain Training Requirements to Support Use of the Dolphin Safe Label 
on Tuna Products, 81  Fed. Reg. 15,44 4 (23  March  2016) (2016 Rule) (collectively, the 
2016 implementing regulations); and  
c. the Hogarth  ruling.97 
5.7.  On appeal, Mexico does not challenge the Panels' definition of the 2016 Tuna Measure. 
Consequently, for the purpose of these appellate proceedings, w e too understand the 2016 Tuna 
Measure to comprise the above instruments.  
5.8.  The Panels found that, like the original and 2013 Tuna Measures, the 2016 Tuna Measure 
pursues two objectives: (i)  to ensure that consumers are not misled or deceived about whether t una 
products contain tuna caught in a manner that adversely affects dolphins; and (ii)  to 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 dolph ins.98 Similarly, like its predecessors, the 
2016 Tuna Measure provides that the use of the term "do lphin-safe", or any other term that claims 
or suggests that the tuna contained in a tuna product was harvested using a method of fishing that 
is not harmful to dolphins , is prohibited if the tuna was not harvested and processed in compliance 
with the applicable labelling conditions.99 Thus, like its predecessors, t he 2016  Tuna Measure 
prohibits the use of the dolphin -safe label on a tuna product sold in the US market unless the 
conditions specified in the measure are met.  
5.9.  The 2016 Tuna Measure broadly places three types of conditions on the use of the dolphin -safe 
label for tuna products exported from or offered for sale in the United  States : (i) conditions rela ting 
to the automatic disqualification of certain tuna products  (eligibility criteria); (ii)  conditions relating 
to certifications (certification requirements); and (iii)  conditions relating to record keeping and the 
segregation of dolphin -safe and non -dolphin-safe tuna  (tracking and verification requirements).100 
Additionally, the certification requirements and tracking and verification requirements, applicable to 
fisheries other than the ETP large purse seine fishery, may become stricter in certain circumst ances, 
owing to an element of the 2016  Tuna Measure referred to as the "determination provisions ".101 
5.10.   As regards the eligibility criteria, the DPCIA excludes from bearing the "dolphin -safe" label 
tuna products "exported from or offered for sale in the United  States " containing either: (i)  tuna 
harvested on the high seas by a vessel engaged in driftnet fishing; or (ii)  tuna harvested by vessels 
using purse seine nets to encircle, or "set on", dolphins anywhere in the world.102 The DPCIA's 
disqualification of tun a products containing  tuna caught by setting on dolphins was briefly 
suspended, in 2002 and 2003, following administrative action by the U nited States  Secretary of 
                                                
96 Panel Reports, para.  7.47 and supra , fn 65. 
97 Panel Reports,  para. 2.1. 
98 Panel Reports, paras.  7.49, 7.186, and 7.705. See  also Appellate  Body Report,  US – Tuna II (Mexico) , 
para. 302; Original Panel Report, paras.  7.401 and 7.425.  
99 Panel Reports, para.  2.4 (referring to DPCIA (Panel Exhibits MEX -1 and USA -1), Se ction 1385(d); 
2016 implementing regulations (Panel Exhibits MEX -2 and USA -2), Section  216.91(a)). See also ibid., 
para. 7.49. 
100 Panel Reports, para.  7.70; First Compliance Panel Report, para.  3.33. 
101 Panel Reports, paras.  7.67-7.69 (referring to 2016 impl ementing regulations (Panel Exhibits MEX -2 
and USA -2), Section  216.91(a)(3)(v)). As further explained in paragraph 5.15 below, the 2013 Tuna Measure 
also contained certain determination provisions, elements of which were modified under the 2016 Tuna 
Measur e. 
102 DPCIA (Original Panel Exhibit US -5), Section  1385(b) -(d). WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Commerce.103 However, the Hogarth  ruling overturned that action and restored thi s condition of  
access to the US  dolphin -safe labelling regime.104  
5.11.   The 2016 Tuna Measure makes no changes to the eligibility criteria set out in the DPCIA  and 
the Hogarth  ruling . Thus, under  the 2016 Tuna Measure , the following tuna products are 
automatically ineligible for the dolphin -safe label: (i)  tuna harvested using large -scale driftnets on 
the high seas; and (ii)  tuna product s containing tuna harvested by setting on dolphins anywhere in 
the world.105 All other tuna products may be labelled d olphin -safe only if  no dolphins were killed or 
seriously injured in the gear deployments in which the tuna was caught. To this end, these tuna 
products must satisfy the certification and tracking and verification requirements of the 2016 Tuna 
Measure.106 
5.12.   Apart from large -scale driftnet fishing on the high seas107, the certification requirements under 
the 2016 Tuna Measure make a distinction between the ETP large purse seine108 fishery109, on the 
one hand, and all other fisheries, on the other hand.110 For tuna caught  in the ETP large purse seine 
fishery, the 2016 Tuna Measure, like the 2013 Tuna Measure, mandates that certification must be 
                                                
103 In 1997, the US Congress adopted the International Dolphin Conservation Program Act (IDCPA), 
which attempted to amend the DPCIA and change the criterion of accessing the US dolphin -safe label  from 
"no encirclement of dolphins" (i.e. no setting on dolphins) to "no dolphin mortality  or serious injury", akin to 
the standard under the AIDCP as described in paragraph 5.5 above. However, the US Congress made this 
amendment of the DPCIA contingent up on the outcome of scientific studies on the effects of setting on 
dolphins, to be undertaken by US  agencies in cooperation with the IATTC. On 31  December 2002, the 
US Secretary of Commerce determined that there was insufficient evidence to conclude that in tentional 
encirclement of dolphins with purse seine nets was having a significant adverse effect on "depleted dolphin 
stock in the  ETP". (Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  6.9 and fn  127 
thereto)  
104 The determinatio n by the US Secretary of Commerce was challenged in the US District Court for the 
Northern District of California by the Earth Island Institute and a number of other organizations. The court 
ruled in Earth Island Institute v. Evans that the Secretary's fin ding was "arbitrary, capricious, an abuse of 
discretion, or otherwise not in accordance with the law". The court also clarified that "dolphin -safe" shall 
continue to mean that: (i)  no tuna was caught on the trip in which such tuna was harvested using a pur se 
seine net intentionally deployed on or used to encircle dolphins; and (ii)  no dolphins were killed or seriously 
injured during the sets in which the tuna was caught. (Appellate  Body Report, US – Tuna II (Mexico) 
(Article  21.5 – Mexico) , para. 6.9 and fn  128 thereto (referring to Earth Island Institute v. Evans , 34 ELR 
20069 (N.D.  Cal. 2004) (Original Panel Exhibit MEX -29), pp.  23-24)) On 13  July 2007, the ruling in Earth 
Island Institute v. Evans  was affirmed on appeal in United States Court of Appeals f or the Ninth Circuit, Earth 
Island Institute et al. v. William T.  Hogarth , 484 F.3d 1123 (9th Cir. 2007) and 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) (Panel 
Exhibit MEX -3) (Hogarth  ruling).  
105 Panel Reports, para.  7.50 (referring to DPCIA (Panel Exhibits MEX -1 and USA -1), Section  1385(d); 
2016 implementing regulations (Panel Exhibits MEX -2 and USA -2), Section  216.91(a)).  
106 Panel Reports, para.  7.50. 
107 Panel Rep orts, para. 7.51 and fn 88 thereto (referring to 2016 implementing regulations (Panel 
Exhibits MEX -2 and USA -2), Section  216.91(a)(3)).  
108 Large purse seine vessels are defined as vessels with a carrying capacity greater than 363  metric 
tons. See supra , fn 93. 
109 As the Appellate  Body in the first compliance proceedings noted, for the purpose 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. (Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , 
fn 130 to para.  6.10)  
110 Panel Reports, paras. 7.51 and 7.54 (referring to 2016 implementing regulations, 
Section  216.91(a)(1) and (3) (Panel Exhibi ts MEX -2 and USA -2)). This differs from the 2013 Tuna Measure, 
which distinguished between three general categories of fisheries: (i)  large purse seine vessels in the ETP (the 
ETP large purse seine fishery); (ii)  purse seine vessels outside the ETP (the no n-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. (See Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  6.10-6.11 
(referring to DPCIA (First Compliance Panel Exhibit MEX -8), Section  1385(d)(1)(B) -(D) and 
Section  1385(d)(2); 2013 implementing regulations (First Compliance Panel Exhibit US -2), 
Section  216.91(a)(1) -(2) and (4)))  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  provided by the captain of the vessel and an International Dolphin Conservation Program111 
(IDCP) -approved observer , indicating that: (i)  none of the tuna was caught on a trip using a purse 
seine net intentionally deployed on or used to encircle (i.e. set on) dolphins; and (ii)  no dolphins 
were killed or seriously injured during the sets in which the tuna was caught.112 
5.13.   As for all fi sheries other than the ETP large purse seine fishery, for fishing trips that began on 
or after 21  May 2016, captains  of all vessels must certify that: (i)  no purse seine net or other fishing 
gear was intentionally deployed on or used to encircle (i.e. set on) dolphins during the fishing trip in 
which the tuna was caught; and (ii)  no dolphins were killed or seriously injured in the sets or other 
gear deployments  in which the tuna was caught.113 Additionally, under the 2016 Tuna Measure, the 
captains of the ves sels in all fisheries other than  the ETP large purse seine fishery must certify that 
they have completed the National Marine Fisheries Service (NMFS) Tuna Tracking and Verification 
Program dolphin -safe training course (Captain Training Course).114 In additio n to the captain's 
certification, in certain circumstances, certifications from an observer participating in a national or 
international programme acceptable to the Assistant Administrator115 will be required pursuant to 
the following two elements of the 201 6 Tuna Measure.  
5.14.   The first element concerns seven US  domestic fisheries for which the Assistant Administrator 
has determined that  observers are qualified and authorized to make the relevant certifications.116 
In these fisheries, certification by such an observer is required when the observer is already on 
board the fishing vessel for other reasons (i.e. reasons unrelated to the dolphin -safe labelling 
regime).117  
5.15.   The second element concerns what the first compliance panel described as the "determination 
provisions"  under the 2013 Tuna Measure .118 The 2013  Tuna Measure provided that the Assistant 
Administrator could make a determination : (i) within a  non-ETP purse seine fishery, that there is a 
regular and significant association between dolphins and tuna, simi lar to the association between 
dolphins and tuna in the ETP; or (ii)  with respect to non-purse seine vessels in any ocean area and 
small purse seine vessels in the ETP, that there is a regular and significant mortality or serious injury 
of dolphins.119 In those situations, not only the captain of the vessel but also an observer had to 
                                                
111 The United States explained in the first compliance  proceedings that the IDCP was established by the 
AIDCP. According to the United States, one of the tools of enforcing the IDCP is the on -board observer 
program that is described in Annex  II to the AIDCP. Pursuant to Annex  II, an observer must be on  board a 
large purse seine vessel in the ETP during each fishing trip. The observer must: (i)  have completed the specific 
training required by the guidelines established under the AIDCP; (ii)  be a national of one of the IATTC parties; 
and (iii) be included in the  list of observers maintained by the IATTC or, if part of a national observer program, 
by the party maintaining such a program. (United  States' appellant's submission in the first compliance 
proceedings, paras.  65-66; AIDCP, as amended October 2009, Articl e I:8 and Annex  II, paras.  1-3 (First 
Compliance Panel Exhibit MEX -30)) 
112 Panel Reports, para.  7.54 (referring to 2016 implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(1) and (b)(2)(iii)). See also 2016 implementing regulations (Panel Exhibits MEX -2 
and USA -2), Section  216.92.  
113 Panel Reports, paras.  7.51 and 7.53 (referring to 2016 implementing regulations (Panel Exhibits 
MEX-2 and USA -2), Section  216.91(a)(3)).  
114 Panel Reports, para.  7.53 (referring to 2016 implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(3)(iii)(B)).  
115 United States Assistant Administrator for Fisheries, NMFS, NOAA, or his/her designee. ( United  States 
Code of Federal R egulations , Title 50, Section  216.3  (First Compliance Panel Exhibit MEX -20)) 
116 In the first compliance panel proceedings, the United  States identified the seven domestic fisheries 
where tuna is regularly harvested as: (i)  American Samoa Pelagic Longline Fi shery; (ii)  Atlantic Bluefin Tuna 
Purse Seine Fishery; (iii)  Atlantic Highly Migratory Species Pelagic Longline Fishery; (iv)  California Deep -set 
Pelagic Longline Fishery; (v)  California Large -mesh Drift Gillnet Fishery; (vi)  Hawaii Deep -set Longline Fishe ry; 
and (vii)  Hawaii Shallow -set Longline Fishery. (United  States' second written submission to the first compliance 
panel, para.  128 and fn  244 thereto (referring to Determination of Observer Programs as Qualified and 
Authorized by the Assistant Administr ator for Fisheries, United States Federal Register , Vol. 79, No. 134 
(14 July 2014) (First Compliance Panel Exhibit US -113), p. 40720). See also United States' appellee's 
submission, fn 679 to para. 624)  
117 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. (See First Compliance Panel Report, para. 3.46; Appellate Body Report,  
US – Tuna II (Mexico) (Article 21.5 – Mexico) , para. 6.23 and fn  171 thereto. See also para. 6. 173 and fn 613 
below)  
118 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  6.11 (referring to First 
Compliance Panel Report, paras.  7.249 and 7.256).  
119 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  6.11 (referring to First 
Compliance Panel Report, paras.  7.249 and 7.256).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  certify that: (i)  no fishing gear was intentionally deployed on or used to encircle dolphins during the 
trip on which the tuna was caught; and (ii)  no dolphins were killed or se riously injured in the sets or 
other gear deployments in which the tuna was caught.120 
5.16.   The determination provisions have been modified under the 2016 Tuna Measure. Pursuant to 
the 2016 Tuna Measure, tuna caught in all fisheries other than  the ETP large purse  seine fishery121 
may require an observer certification, in addition to the captain certification described in 
paragraph  5.13 above , where the Assistant Administrator has determined that in such a fishery: 
(i) there is a regular and significant association between dolphins and tuna (similar to the association 
between dolphins and tuna in the ETP); or (ii)  a regular and significant mor tality or serious injury of 
dolphins is occurring. In those situations, both the captain and the observer must certify that: 
(i) no purse seine net or other fishing gear was intentionally deployed on or used to encircle (i.e. set 
on) dolphins during the tr ip on which the tuna was caught;  and (ii)  no dolphins were killed or 
seriously injured in the sets or other gear deployments in which the tuna was caught.122 
5.17.   As was the case with the 2013 Tuna Measure, the tracking and verification requirements 
under the 201 6 Tuna Measure concern the physical segregation of dolphin -safe tuna from 
non-dolphin -safe tuna, from the moment of harvest and throughout the processing chain.123 
Specifically , like its predecessor, the 2016 Tuna Measure prescribes the documentation require ments 
for recording and verifying segregation and the corresponding regulatory oversight. These 
requirements distinguish between: (i)  the ETP large purse seine fishery, which must comply with the 
AIDCP Tracking and Verification System124; and (ii)  all other fisheries, which must comply with  the 
requirements prescribed in the 2016 implementing regulations  that the United  States  refers to as 
the "NOAA  regime".125 Thus, the ETP large purse seine fishery is subject to the AIDCP regime, while 
all other fisheries are subject to the NOAA regime.  
5.18.   The AIDCP Tracking and Verification System is based on the use of Tuna Tracking Forms 
(TTFs). Every TTF has a unique number. On every fishing trip, ETP large purse seine vessels must 
maintain two TTFs, one to record tuna harvested in dolphin -safe sets, and one to record tuna 
harvested in non -dolphin -safe sets.126 At the end of each fishing trip, the IDCP -approved  observer  
and the captain of the fishing vessel initial  both TTFs to certify that the information on the forms is 
accurate.127  
5.19.   At the time of unloading, the relevant TTF must be transmitted to the competent authority of 
an AIDCP party.128 The relevant TTF number must then acco mpany the tuna through sales of portions 
                                                
120 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  6.10-6.11. The 
Appellate  Body upheld the first compliance panel's findings that the determination prov isions in the 2013 Tuna 
Measure were not even -handed. The first compliance panel found that the design of the determination 
provisions meant that, in some cases, fisheries other than the ETP large purse seine fishery may be treated 
differently, and less st ringently, 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 serious 
injury, on the one hand, or the degree of tuna -dolphin assoc iation, on the other hand. (Appellate  Body Report, 
US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.182, 7.188, and  8.1.a.v; First Compliance Panel 
Report, para.  7.263)  
121 We recall that, under the 2013 Tuna Measure, these fisheries were further subd ivided into: (i)  the 
non-ETP purse seine fishery; and (ii)  non-purse seine vessels in any ocean area and small purse seine vessels 
in the ETP. (See para. 5.15 above and supra , fn 110. See also Appellate  Body Report, US – Tuna II (Mexico) 
(Article  21.5 – Mexico), paras.  6.10-6.11)  
122 Panel Reports, paras.  7.51 and 7.68 (referring to 2016  implementing regulations (Panel Exhibits 
MEX-2 and USA -2), Section  216.91(a)(3)(v)).  
123 Panel Reports, paras. 7.55 -7.66. 
124 Panel Reports, paras.  7.56-7.61. See also 2016  imple menting regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.93(a) -(c)(1).  
125 Panel Reports, para.  7.62 (quoting United  States' first written submission to the Panels, para.  143). 
See also ibid., paras. 7.63 -7.67; 2016  implementing regulations (Panel E xhibits MEX -2 and USA -2), 
Section  216.91(4) -(5) and Section  216.93(c)(2) -(4). 
126 Panel Reports, para.  7.57 (referring to International Dolphin Conservation Program, System for 
Tracking and Verifying Tuna, as amended (2015) (Panel Exhibit USA -90), Section 3( 2); Appellate  Body Report, 
US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  6.19).  
127 Panel Reports, para.  7.57 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  6.19).  
128 Panel Reports, para.  7.59 (referring to I nternational Dolphin Conservation Program, System for 
Tracking and Verifying Tuna, as amended (2015) (Panel Exhibit USA -90), Section  5(2)-(5)). WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  of the catch and through every processing step of those portions.129 A tuna product exported as 
AIDCP dolphin -safe must be accompanied by a certificate of its dolphin -safe status issued by a 
competent authority, which  must also include a reference to the relevant TTF number.130 The AIDCP 
Tracking and Verification System also provides that the national programs established by the parties 
to the AIDCP should include periodic audits and spot checks for tuna products, as wel l as mechanisms 
for cooperation among national authorities.131 
5.20.   In addition, all tuna products imported into the United  States , regardless of where the tuna 
was caught and whether the dolphin -safe label is used, must be accompanied by NOAA  Form 370, 
which des ignates, inter alia, whether the tuna is dolphin -safe.132 This means that, for imported tuna 
caught in the ETP large purse seine fishery, both TTFs and Form 370 are required. By contrast, for 
imported tuna caught in all other fisheries, only Form 370 is requ ired. 
5.21.   Moreover, as regards all other fisheries, the NOAA regime requires US tuna processors to 
submit monthly reports to the US Tuna Tracking and Verification Program  for all tuna received at 
their processing facilities. These reports contain the same info rmation contained in NOAA Form 370, 
as well as additional information, such as unloading dates and the condition of the tuna products.133 
Furthermore, under the NOAA  regime, the NMFS is empowered to undertake verification activities, 
including dockside inspe ctions of vessels, monitoring of Form 370s, monitoring of cannery reports, 
audits of US canneries, and retail market spot checks.134 Other US agencies may also conduct 
on-board inspections on the high seas and in US waters.135 
5.22.   Furthermore, while the 2016 Tuna Measure has made no changes to the tracking and 
verification requirements applicable to the ETP large purse seine fishery, it has introduced some 
additional requirements under the NOAA regime , which governs all other fisheries. As the Panels 
observed, the 2016 Tuna Measure establishes new chain of custody record -keeping requirements 
for tuna products harvested from all other fisheries. Specifically, the US processors and importers 
of such tuna products must collect and retain, for two years, information on each point in the chain 
of custody of the tuna or tuna products, including information on all storage facilities, trans -shippers, 
processors, and wholesalers or distributors. Th is information must be provided to the NMFS upon 
request, and must be sufficien t for the NMFS to conduct a trace -back of any tuna product marketed 
as dolphin -safe to verify that the tuna product in fact meets the dolphin -safe labelling requirements. 
These new requirements apply to all tuna products labelled dolphin -safe if those prod ucts contain 
tuna harvested on a fishing tr ip beginning on or after 21  May 2016.136 
5.23.   Importantly, the breach of these new chain of custody record -keeping requirements may lead 
to the imposition of sanctions under US law. Sanctions for offering for sale or exp ort tuna products 
falsely labelled dolphin -safe may be assessed against any producer, importer, exporter, distributor, 
or seller that is subject to the jurisdiction of the United  States .137 They may be prosecuted under 
                                                
129 Panel Reports, para.  7.59 (referring to International Dolphin Conservation Program, System for 
Tracking and Ve rifying Tuna, as amended (2015) (Panel Exhibit USA -90), Section  5(7)).  
130 Panel Reports, para.  7.59 (referring to International Dolphin Conservation Program, System for 
Tracking and Verifying Tuna, as amended (2015) (Panel Exhibit USA -90), Section  6(d)).  
131 Panel Reports, para.  7.60 (referring to International Dolphin Conservation Program, System for 
Tracking and Verifying Tuna, as amended (2015) (Panel Exhibit USA -90), Section 7).  
132 Panel Reports, para.  7.63 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  6.13; Taking and Related Acts Incidental to Commercial Fishing Operations by 
Tuna Purse Seine Vessels in the Eastern Tropical Pacific Ocean, United States Code of Federal Regulations , 
Title 50, Section 216.24 (2016)  (Panel Exhibit USA -3), Section  216.24(f)(2)(i) -(ii); 2016 implementing 
regulations (Panel Exhibits MEX -2 and USA -2), Section  216.93(f); NOAA Form 370 (Panel Exhibit USA -4)). 
133 Panel Reports, para.  7.64 (referring to Original Panel Report, para.  2.32; 2016  implementing 
regulations (Panel Exhibits MEX -2 and USA -2), Section  216.93(d) -(e)). 
134 Panel Reports, para.  7.64 (referring to 2016  implementing regulations (Panel Exhibits  MEX-2 and 
USA-2), Section  216.93(d)(1) -(3), (f), and (g)(3)).  
135 Panel Reports, para.  7.64. 
136 Panel Reports, para.  7.65 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(5)).  
137 Panel Reports, para.  7.66 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.93 (g)(3); NOAA Form 370 (Panel Exhibit USA -4); United  States' response to Panel 
question No.  29, paras.  148-149).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the DPCIA provisions, the federal provi sions prohibiting false statements and smuggling, or the 
federal labelling standards.138 
5.24.   Additionally, in fisheries where the Assistant Administrator has made a determination under 
the determination provisions described in  paragraph 5.16 above, the following  conditions apply. Any 
imported tuna or tuna product made from tuna caught on a trip, in those fisheries, beginning on or 
more than 60  days after the publication of a notice of the determination in the Federal Register , and 
which is intended to be labelled  as dolphin -safe, must be accompanied by valid documentation signed 
by a representative of the vessel flag nation or the processing nation (if  processed in another nation) 
certifying that: (i)  the catch documentation recorded on NOAA Form 370 is correct; ( ii) the tuna or 
tuna products meet the US dolphin -safe labelling standards; and (iii)  the chain of custody 
information is correct.139 
5.25.   In sum, we observe that the eligibility criteria, the certification requirements, and the tracking 
and verification requirem ents all form part of a single measure, the 2016 Tuna Measure, and thus 
work together in pursuing the same objectives. Hence, following the Appellate  Body's finding s in the 
first compliance proceedings, in our review of the Panels' evaluation of the 2016 T una Measure, we 
"take account of the fact that its various elements – the eligibility criteria, the certification 
requirements, and the tracking and verification requirements – establish a series of conditions of 
access to the dolphin -safe label that are c umulative and highly interrelated".140 
6  ANALYSIS OF THE A PPELLATE  BODY  
6.1  Article  2.1 of the TBT Agreement  
6.1.1   Introduction  
6.1.  As noted above, in the present compliance proceedings, the United  States  requested the Panels 
to find that the 2016 Tuna Measure is consistent with Article  2.1 of the TBT Agreement . Mexico 
asked the Panels to find that the 2016 Tuna Measure is inconsistent with the same provision. The 
Panels recalled that a finding of inconsis tency with Article  2.1 must be based on the following three 
elements: (i)  the measure at issue is a technical regulation within the meaning of Annex 1.1 to the 
TBT Agreement ; (ii) the relevant products are "like" products; and (iii)  the measure at issue ac cords 
less favourable treatment to imported products than to the relevant group of like products.141 Noting 
the similarity in the factual circumstances underlying the first two elements in the first compliance 
proceedings, the Panels in these compliance proc eedings agreed with the parties that the 2016 Tuna 
Measure is a technical regulation and that the relevant products are  like.142 
6.2.  Regarding the third element, the Panels recalled the Appellate  Body's finding that assessing 
whether the measure accords less fav ourable treatment under Article  2.1 requires  two distinct steps: 
(i) determin ing whether the challenged measure modifies the conditions of competition to the 
detriment of the relevant imported products vis-à-vis like products of domestic origin and/or like  
products originating in any other country; and, if the  panel makes such a finding, (ii) determin ing 
whether the detrimental impact on imports stems exclusively from a legitimate regulatory distinction 
rather than reflecting discrimination against the grou p of imported products.143 The Panels noted 
that the 2016  Tuna Measure maintains the overall architecture and structure of the original and 
                                                
138 Panel Reports, para.  7.66 (referring to NOAA Form 370 (Panel Exhibit USA -4); United States Code , 
Title 18, Section 545 (Panel Exhibit USA -166); United States Code , Title 18, Section 3571 (Panel Exhibit 
USA-167); United States Code , Title 16, Section 3372 (Panel Exhibit USA -169), Section 3372(d); Civil 
Monetary Penalty Adjustments for Inflation, United States Federal Register , Vol. 81, No. 109 (7  June 2016) 
(Panel Exhibit USA -170); United States Code , Title 16, Section 3373 (Panel Exhibit USA -171), 
Section  3373(d)(3); United  States Code , Title  16, Section 3374 (Panel Exhibit  USA-172), Section 3374(a)(1); 
United States Code , Title 18, Section 1001 (Panel Exhibit USA -173), Section 1001(a); United States Code , 
Title 16, Section 1375 (Panel Exhibit USA -174), Sections  1375(a)(1) and 1375(b))).  
139 Panel Reports, para.  7.69 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Secti on 216.91(a)(5)(ii)).  
140 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.166.  
141 Panel Reports, para.  7.73 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.25).  
142 Panel Reports, para. 7.74. 
143 Panel Reports, para.  7.73 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.26).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  2013 Tuna Measures and that the parties agreed that the relevant factual situation has not changed 
from the original o r the first compliance proceedings.144 The Panels thus found that, by excluding 
most Mexican tuna products from accessing the dolphin -safe label, while granting conditional access 
to such label to like  products from the United  States  and other countries, the  2016 Tuna Measure, 
like the original and the 2013 Tuna Measures, modifies the conditions of competition to the detriment 
of Mexican tuna products in the US  market.145  
6.3.  The Panels therefore noted that the parties' disagreement on the consistency of the 2016 Tuna 
Measure with Article 2.1 of the TBT Agreement centred on the question whether the detrimental 
impact caused by the 2016 Tuna Measure stems exclusively from a legi timate regulatory distinction. 
The Panels understood their task in these proceedings to be ascertaining "whether the relevant 
regulatory distinctions are appropriately 'calibrated' and 'tailored' to, and commensurate with", the 
different risks to dolphins arising from the use of different fishing methods in different areas of the 
ocean .146  
6.4.  The Panels went on to establish "the risk profiles of the relevant fishing methods in different 
areas of the ocean, taking into account data on both observable and unobser vable harms".147 
Thereafter, the  Panels examined whether the 2016 Tuna Measure, including its relevant constituent 
elements, is calibrated to different risks to dolphins . In this regard, the Panels examined, 
sequentially, the eligibility criteria, the certif ication requirements, the tracking and verification 
requirements, and the determination provisions148, before providing an overall assessment of the 
consistency of the 2016 Tuna Measure with Article  2.1.149  
6.5.  On appeal, Mexico claims that the Panels erred in th eir interpretation and application of 
Article  2.1 of the TBT Agreement  in finding that the 2016 Tuna Measure is not inconsistent with that 
provision. Mexico raises four main grounds of appeal. First, Mexico contends that the Panels relied 
on a legal standa rd that fails to take into account whether the regu latory distinctions of the 
2016 Tuna Measure are rationally related to its objectives. In this regard, Mexico argues that the 
Panels erred in their calibration analysis because they failed to consider the risks of inaccurate 
labelling under the 2016 Tuna Measure.150 Second, Mexico contends that the Panels erred in their 
application of Article  2.1 by limiting aspects of their calibration analysis to a comparison of the risk 
profiles of different fishing method s.151 Third, Mexico alleges that the Panels erred in their 
assessment of the risks to dolphins arising from the use of different fishing methods in different 
areas of the ocean by: (i)  failing to adequately evaluate the risk profiles of different fisheries152; 
(ii) using setting on dolphins in the ETP as the benchmark153; and (iii)  ignoring relevant 
measurements of risks.154 Fourth, Mexico alleges that the Panels erred in the ir application of 
Article  2.1 of the TBT Agreement  in finding that the eligibility criteria , the certification requirements, 
the tracking and verification requirements, as well as the 2016  Tuna Measure as a whole, are 
calibrated to the risks to dolphins arising from the use of different fishing methods in different areas 
of the ocean.155 
6.6.  The Unite d States  claims that the Panels correctly determined that the regulatory distinctions 
of the 2016 Tuna Measure are properly calibrated to different risks to dolphins arising from the use 
of different fishing methods in different areas of the oceans, based on the Appellate  Body's guidance 
in the first compliance proceedings. First, the United  States  contends that, in the first  compliance 
proceeding s, the Appellate  Body examined the interplay between the rational connection and 
calibration analyses and made clear that, in this dispute, the concept of calibration "reflects the 
                                                
144 Panel Reports, para. 7.77.  
145 Panel Reports, para.  7.78 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.238).  
146 Panel Reports, para.  7.103 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.252).  
147 Panel Reports, para.  7.149.  
148 In response to questioning at the hearing, Mexico and the  United  States agreed that the Panels acted 
appropriately in undertaking this sequential analysis.  
149 Panel Reports, para.  7.529.  
150 Mexico's Notice of Appeal, para. 8.a; appellant's submission, paras.  99-142. 
151 Mexico's Notice of Appeal, para. 8.b; appellan t's submission, paras.  159-172, 181 -185, and 230 -234. 
152 Mexico's Notice of Appeal, para. 8.c; appellant's submission, paras.  162-171 and  235-240. 
153 Mexico's Notice of Appeal, para. 8.c; appellant's submission, paras.  175-191. 
154 Mexico's Notice of Appeal, para. 8.c; appellant's submission, paras.  192-225 and  241-246. 
155 Mexico's Notice of Appeal, para. 9; appellant's submission, paras.  226-307. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  nexus between the distinctions of the measure and the measure's objective [s]".156 Second, in the 
United States ' view, the Panels acted in accordance with the requirements of Article  2.1 in examining 
the relevant regulatory distinctions under the 2016 Tuna Measure.157 Third, the United  States  also 
considers that the Panels appropriately examined the risk profiles of fishing methods and fisheries.158 
Fourth, the United  States  submits that the Panels' "intermediate conclusions" concerning the 
eligibility criteria, certification requirements, and tracking and verification requirements were 
"correct and not in e rror".159 The United  States  adds that, contrary to Mexico's arguments, the 
Panels' overall assessment of the 2016 Tuna Measure was not only based on their intermediate 
analyses but also their examination as to how the different parts of the measure interact to address 
the risk s to dolphins arising from the use of different fishing methods in different ocean areas.160  
6.7.  We begin by briefly recalling the relevant legal standard under Article  2.1, before assessing  
whether the Panels erred in their articulation ther eof. Thereafter, we turn to  the Panels ' application 
of that standard in the context of this dispute , by first address ing Mexico's two overarching 
arguments regarding the Panels' analysis under Article  2.1, namely , that the Panels: (i)  failed to 
examine the  nexus between the regulatory distinctions under the measure at issue and its 
objectives; and (ii)  erred by limiting aspects of their calibration analysis to a comparison of the risk 
profiles of different fishing methods. Next, we address  Mexico's arguments pertaining to specific 
aspects of the Panels' assessment of risk profiles, including the allegations that the Panels did not 
adequately assess the risks arising from tuna fishing in different fisheries, adopted a wrong 
benchmark, and ig nored relevant measurements of risks. Finally, we examine  Mexico's arguments 
that the Panels erred in concluding that the eligibility criteria, certification requirements, and tracking 
and verification requirements, as well as the 2016 Tuna Measure a s a wh ole, are calibrated to the 
relevant risk profiles.  
6.1.2   "Treatment no less favourable" under Article  2.1 of the TBT Agreement  
6.1.2.1   Whether the Panels erred in their articulation of the legal standard  
6.8.  Article  2.1 of the TBT Agreement  provides that:  
Members shall ensure that in respect of technical 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.  
6.9.  The Appellate  Body has identified a two -step analysis for examining whether the technical 
regulation at issue accords less favourable treatment to imported products under Article  2.1 of the 
TBT Agreement : (i) whether it modifies the conditions of competit ion to the detriment of such 
imported products vis -à-vis like products of domestic origin and/or like products originating in any 
other country; and (ii) whether the detrimental impact on imports stem s exclusively from a 
legitimate regulatory distinction.161 Where the detrimental impact caused by a technical regulation 
is found to stem exclusively from a legitimate regulatory distinction, "such a technical regulation 
does not accord less favourable treatment to imported products and is therefore consistent wi th 
Article  2.1 of the TBT Agreement ."162  
6.10.   To determine whether the detrimental impact stems exclusively from a legitimate regulatory 
distinction, "a panel must carefully scrutinize whether the techni cal regulation at issue is 
                                                
156 United  States' appellee's submission, para. 32 (referring to Appellate  Body Report, US – Tuna II 
(Mexico) (Articl e 21.5 – Mexico) , paras. 7.92, 7.98, and 7.101. See also ibid., paras.  35-85. 
157 United  States' appellee's submission, paras. 116 -123. 
158 United  States' appellee's submission, paras. 96 -203. 
159 United  States' appellee's submission, para.  353. See also ibid., paras. 204 -353. 
160 United  States' appellee's submission, para.  354. 
161 See Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.26 (referring to 
Appellate  Body Reports, US – Clove Cigarettes , paras.  180, 182, and 215; US – COOL , para s. 268 and 271;  
US – Tuna II (Mexico) , para.  215).  
162 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.96. In interpreting 
Article  2.1 as such, the Appellate  Body took into account the context provided by the definition of "tec hnical 
regulation" found in Annex  1.1 to the TBT  Agreement, as well as Article  2.2 and the sixth recital of the 
preamble of the TBT  Agreement. (Ibid., para. 7.87. See also Appellate  Body Reports, US – COOL , para.  271; 
US – Clove Cigarettes , paras.  171-174; US – Tuna II (Mexico) , paras.  212-213) WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  even-handed in its design, archi tecture, revealing structure, operation, and application in the light 
of the particular circumstances of the case."163 The Appellate  Body has found that there may be 
different ways to demonstrate that a measure does not stem exclusively from a legitimate reg ulatory 
distinction , including, "for  example", by showing that  the measure is applied in a manner that 
constitutes arbitrary or unjustifiable discrimination.164 At the same time, the Appellate  Body has 
emphasized that "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".165  
6.11.   The Appellate  Body has said that, in light o f the "important parallels" between the analyses 
under Article  2.1 of the TBT Agreement and the chapeau  of Article  XX of the GATT  1994166, relevant 
jurisprudence under the latter, p articularly that relating to th e concept of "arbitrary or unjustifiable 
discrimination", may provide useful insight as to how the concept  should be understood in the 
context of the second  step of the "treatment no less favourable" analysis under Article  2.1.167 In this 
connection, "[o]ne of the most important factors in the assessment of arbitrary or unjustifiable 
discrimination [under the chapeau  of Article  XX] is the question of whether the discrimination can 
be reconciled with, or is rationally related to, th e policy objective with respect to which the measure 
has been provisionally justified under one of the subparagraphs of Article  XX."168 To the 
Appellate  Body, the "same considerations … are valid in the context of the second step of the analysis 
of 'treatmen t no less favourable' under Article  2.1".169 Thus, for the purpose of Article  2.1 of the 
TBT Agreement , in examining whether a technical regulation constitutes a means of arbitrary or 
unjustifiable discrimination, "it is likely that this assessment [will] in volve[] consideration of the 
nexus between the regulatory distinctions found in the measure and the measure's policy 
objectives"170, although "consideration of other factors  … may also be relevant to the analysis ."171  
6.12.   In the original proceedings, the United  States sought to demonstrate that the detrimental 
impact under the original Tuna Measure stemmed exclusively from a legitimate regulatory distinction 
by introducing the notion of calibration. More specifically, the United  States  contended that the 
regulator y distinctions drawn under the original Tuna Measure "between different 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".172 This led the Appellate  Body to 
examine the legitimacy of the original Tuna Measure 's regulatory di stinctions "through the lens 
of … 'calibration'".173 The Appellate  Body emphasized that its use of the terms "even -handed" and 
"calibrated":  
[D]id not constitu te different legal tests, since the entire inquiry by the Appellate  Body 
revolved around whether the United  States  had properly substantiated its argument 
                                                
163 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.31 (referring to 
Appellate  Body Report, US – Clove Cigarettes , para.  182). See also Appellate  Body Reports, US – Clove 
Cigarettes , para. 215; US – COOL , para.  340; US – Tuna II (Mexico) , para. 216. 
164 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.31. See also 
Appellate  Body Reports, US – COOL , para.  271; US – COOL (Article  21.5 – Canada and Mexico) , para . 5.94. 
165 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.94. (emphasis original) 
See also ibid., para. 7.31. 
166 Appellate  Body Reports, EC – Seal Products , para.  5.310; US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.89. We recall that the chapeau  of Article  XX of the GATT  1994 provides that 
WTO Members may resort to measures that fall within one of the discrete categories of general exceptions 
contained in Article  XX of the GATT  1994 "[s]ubject 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". Given that the sixth recital of t he 
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 relevant to understanding the content of the second step of the "treatment 
no less favourable" requirement under Article  2.1 of the TBT  Agreement. (Appellate  Body Report, US – Tuna II 
(Mexico) (Article  21.5 – Mexico) , para.  7.88)  
167 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.91. 
168 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.92 (quoting 
Appellate  Body Reports, EC – Seal Products , para.  5.306, in turn referring to Appellate  Body Reports,  
US – Shrimp , para.  165; Brazil – Retreaded Tyres , paras.  227-228 and  232).  
169 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.92. 
170 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.97. 
171 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.95. 
172 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.98. 
173 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.98. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  that the original tuna measure  was even -handed , and thus not inconsistent with 
Article  2.1, because i t was "calibrated"  to the risks to dolphins arising from different 
fishing methods in different areas of the oceans.174 
6.13.   Thus, rather than being a separate legal test, calibration is the means  to assess whether the 
detrimental impact of the measure at issue in this dispute stems exclusively from a legitimate 
regulatory distinction , in the context of the second step of the "treatment no less favourable" analysis 
under Article 2.1 . As we explai n in greater detail in  section 6.1.3 below, if done  properly , the 
calibration analysis should encompass consideration of the rational relationship between the 
regulatory distinctions and the objectives of the 2016  Tuna Measure. Thus, if calibrated  properly , 
these regulatory distinctions will not amount to arbitrary or un justifiable discrimination and will thus 
comply with the requirements of Article  2.1 of the TBT Agreement . 
6.14.   In articulating the applicable legal standard under Article  2.1 in these compliance proceedings, 
the Panels recalled the Appellate  Body's findings as  set forth above. The Panels considered that, 
"while there may in theory be a number of ways" to assess whether the measure satisfies  the second 
step of the analysis under Article  2.1175, in this dispute  it was appropriate to assess whether the 
detrimental i mpact caused by the 2016 Tuna Measure stems exclusively from a legitimate regulatory 
distinction  through the lens of calibration .176  
6.15.   On appeal, Mexico highlights the Appellate  Body's statement that a rational relationship test 
is "[o]ne of the most important factors " in assessing arbitrary and unjustifiable discrimination under 
the chapeau  of Article XX of the GATT 1994.177 Thus, Mexico argues  that, given the "close 
relationship" between the notion of even -handedness under Article  2.1 and the chapeau  of 
Article  XX, "an assessment of whether the detrimental impact can be reconciled with, or is rationally 
related to, the policy objective pursued by the measure" is required in the analysis under 
Article  2.1.178  
6.16.   As indicated above, the assessment of whether the detrimental impact of a measure amounts 
to arbitrary or unjustifiable discrimination in the context of Article  2.1 will likely involve consideration 
of the nexus between the regulatory distinctions of the measure and its objectives. This does not 
mean that such consideration necessarily constitutes a step that is separate and distinct from a 
proper calibration analysis , as Mexico appears to suggest. At the same time, we do not understand 
Mexico's arguments on appeal to relate primarily to the Panels' ar ticulation of the legal standard 
under Article  2.1. Rather, as further discussed in section 6.1.3 below, Mexico  contends that  the 
Panels , in their calibration analysis, failed to include an examination of the nexus between the 
regulatory distinctions givin g rise to the detrimental impact, on the one hand, and the 2016 Tuna 
Measure's objectives, on the other hand. Therefore, while Mexico indicates that its claims relate, 
inter alia , to the Panels' interpretation of Article  2.1, we observe that its arguments mainly concern 
the Panels'  application of th e legal standard  under Article  2.1 in the context of the present dispute. 
We address these arguments in section 6.1.3 below. However, before turning to the issue of what 
constitutes a proper calibration analysis in this dispute, we address Mexico's argument that the 
Panels should have taken into account the objective of sustainable development set out in the 
preamble of the WTO  Agreement  when interpreting and applying Article  2.1 of the TBT Agreement 
in this dispute.  
6.1.2.2   Whether the Panels erred in rejecting Mexico's argument c oncerning the 
relevance of the sustainability of tuna stock  and the marine ecosystem  
6.17.   Before the Panels, Mexico argued  that, "while the reference to sustainable development in the 
preamble of  the WTO Agreement does not itself create any obligations, nevertheless the text of all 
                                                
174 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.98. (emphasis added)  
175 Panel Reports, para.  7.102.  
176 Panel Reports, para. 7.102. The Panels noted that the Appellate Body had, in the first compliance 
proceedings, repeatedly emp hasized that the appropriate way, in the context of this dispute, for a panel to 
assess whether the detrimental impact caused by the Tuna Measure stems exclusively from a legitimate 
regulatory distinction is to assess whether the Measure is properly "calib rated" to different risks to dolphins. 
(See Panel Reports, para.  7.84 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.155))  
177 Mexico's appellant's submission, para.  325 (quoting Appellate  Body Report, US – Tuna II (Mexico) 
(Article  21.5 – Mexico) , para.  7.92). (emphasis added)  
178 Mexico's appellant's submission, para.  86. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  WTO obligations that in any way relate to the objective of sustainable development  or environmental 
protection  must be interpreted and clarified within [the] … context"  provided by the preamble.179 
Therefore, Mexico contend ed that, while WTO  Members are free to choose their own objectives, the  
Members  would be acting inconsistently with their WTO obligations "if the means … to achieve" such 
objectives "are inconsistent wit h the objectives of sustainable development".180 Mexico submit ted 
that the principle of sustainable development has risen to the status of a principle of international 
law applicable to all countries.181  
6.18.   The Panels rejected  Mexico's argument, finding that this argument "appear [ed] to elevate the 
preambular language to the level of substantive obligation, despite Mexico's assertion to the 
contrary".182 Furthermore, the Panels emphasized that the 2016 Tuna Measure is not concerned with 
sustainable development, but  rather with the protection and well -being of dolphins, and that the 
WTO Agreement  does not obligate a Member to regulate only for the objective of "sustainable 
development".183  
6.19.   On appeal, Mexico argues that, where the obligations at issue in a dispute rela te to sustainable 
development, they must be interpreted consistently with the objective of sustainable development. 
For Mexico, this requirement  arises under Article 2.1 in the determination of whether the 2016 Tuna 
Measure stems exclusively from a legitim ate regulatory distinction.184 In Mexico's view, applying a 
technical regulation that is inconsistent with or undermines the objective of sustainable development 
results in "unjustifiable discrimination".185 Mexico highlights that, by encouraging the use of fish 
aggregating devices (FADs) and other forms of tuna fishing outside the ETP as alternatives to the 
fishing method of setting on dolphins, the 2016 Tuna Measure "does grievous harm to fisheries and 
to the overall marine ecosystem" and "must therefore be seen as inconsistent with the objective of 
sustainable development".186 Mexico contends t hat the application of the 2016  Tuna Measure results 
in "unjustifiable discrimination", and therefore that the regula tory distinctions under the measure 
"cannot be 'legitimate '" for the purpose of the second step of the analysis under Article  2.1.187  
6.20.   The United  States  responds that Mexico seek s to transform preambular language regarding 
sustainable development into a subs tantive obligation.188 In addition, the United  States  argues that, 
to make its argument, "Mexico is forced to substantially change the objectives of the 2016 measure" 
and transform the dolphin -protection and consumer -information objectives of the measure int o 
labelling requirements that relate to "the sustainability of tuna stocks and of the marine ecosystem 
generally".189 
6.21.   We observe that the issue raised by Mexico is twofold. First, we must determine whether, 
under the "treatme nt no less favourable " requiremen t in Article  2.1 of the TBT Agreement , the 
means through which a technical regulation achieves its objectives must be compatible with the 
principle of sustainable development in the preamble of the WTO  Agreement . Second, if we find that 
there is such a req uirement under  Article  2.1, we must determine whether, in the circumstances of 
the present dispute, the 2016 Tuna Measure is incompatible with this requirement because it 
encourages the use of FADs and other forms of fishing that are unsustainable for tuna stock.  
6.22.   The Appellate  Body has said that , in assessing whether a technical regulation accords less 
favourable treatment to imported products under  Article  2.1, a panel's  task lies , in part,  in 
ascertaining whether the detrimental impact caused by a technical regulation stems exclusively from 
                                                
179 Panel Reports, para.  7.128. (emphasis added)  
180 Panel Reports, para.  7.128.  
181 Panel Reports, para. 7.128.  
182 Panel Reports, para.  7.130.  
183 Panel  Reports, para.  7.131.  
184 Mexico's appellant's submission, paras. 147 -148. 
185 Mexico's appellant's submission, para.  149. 
186 Mexico's appellant's submission, para. 148. For instance, Mexico argues that the floating object/FAD 
method "attracts and kills immatu re as well as mature tuna, as well as a wide variety of other bycatch, 
including sea turtles, sharks, and other species". (Mexico's appellant's submission, para. 25 (referring to 
Original Panel Report, para. 4.10))  
187 Mexico's appellant's submission, para.  149. 
188 United  States' appellee's submission, para.  91. 
189 United  States' appellee's submission, para.  92 (referring to Mexico's appellant's submission, 
para. 148). (emphasis omitted)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  a legitimate regulatory distinction.190 The Appellate  Body has  also indicated that the preamble of the 
TBT Agreement  informs "the ambi t of the 'treatment no less favourable' requirement in Article  2.1, 
by making clear that technical regulations may pursue the objectives listed therein".191  
6.23.   We consider that the preamble of the WTO  Agreement  may also inform interpretations of the 
covered ag reements in appropriate circumstances. In this regard, the Appellate  Body has found that 
the preamble of the WTO  Agreement  "add[s] colour, texture and shading" to the interpretation of 
the covered agreements.192 Thus, while the preamble of the WTO  Agreement  does not itself create 
substantive obligations, it can provide important context for the interpretation of the covered 
agreements, for example, by shedding light on the kinds of policy objectives a Member may pursue.   
6.24.   We note that the legitimacy of the obj ectives of the 2016  Tuna Measure is not at issue before 
us in this dispute. Indeed, in response to questioning at the hearing, Mexico indicated that it did not 
challenge the right of the United  States  or other WTO Members to determine the objectives of the ir 
measures.193 Mexico  also acknowledge d that "the reference to sustainable development in the 
preamble of the WTO  Agreement  does not itself create any obligations ."194 At the same time , Mexico 
maintains that "[w]here … obligations [at issue in a dispute] relate to sustainable development, they 
must be interpreted consistently with the objective of sustainable development."195 In Mexico's view, 
"this interpretive requirement arises under Article  2.1 of the TBT Agreement " when determining 
whether the detriment al impact under the Tuna Measure stems exclusively from a legitimate 
regulatory distinction.196  
6.25.   Mexico's argument thus appears to be premised on its view that Article  2.1 is an obligation 
that "relate[s] to sustainable development".197 However, Article  2.1 is  concerned with ensuring that 
technical regulations are designed and applied in a manner that affords "treatment no less 
favourable" to like imported products. In our view, Mexico seems to conflate the nature of the  
obligation  in Article  2.1 with the natur e of the  technical regulations  that Members may choose to 
adopt.  For instance, Mexico indicates that "[n]ot all technical regulations will relate to sustainable 
development, but , where they do, they will be inconsistent with [ Article  2.1] if their effects are 
unsustainable ."198 Thus, Mexico's argument appears to suggest that the relevance of the principle 
of sustainable development to the interpretation of Article  2.1 may differ depending on whether a 
measure "relates to", or has "effects" on, sustainable dev elopment. We fail to see why the 
interpretation of Article  2.1 should vary depending on  the kind of technical regulation that a Member 
adopts. While a Member's technical regulation may, depending on the circumstances, relate to 
sustainable development, the  nature and scope of the obligation in Article  2.1 remain unchanged.  
6.26.   In any event, we recall that the objectives of  the 2016 Tuna Measure are: (i)  to ensure that 
consumers are not misled or deceived about whether tuna products contain tuna caught in a man ner 
that adversely affects dolphins; and (ii)  to 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.199 Given that the legitimacy of the objectives of the 2016  Tuna Measure is not at 
issue in these compliance proceedings, we consider that the question before the Panels was whether 
                                                
190 See para. 6.9 above.  
191 Appellate  Body Report, US – Clove Cigarettes , para. 173.  
192 Appellate  Body Report, US – Shrimp , para.  153. We recall that, in US – Shrimp , the Appellate  Body 
relied on the objective of sustainable development contained in the preamble of the WTO  Agreement to 
determine whether a measure aimed at protecting  sea turtles could fall within the ambit of the policy objective 
of conservation of "exhaustible natural resources" within the meaning of Article  XX(g) of the GATT  1994. The 
Appellate  Body indicated that the expression "exhaustible natural resources" conta ined in this provision should 
be read in light of the objective of sustainable development contained in the preamble of the WTO  Agreement, 
and interpreted to refer not only to the conservation of exhaustible mineral or other non -living natural 
resources bu t also to living natural resources including sea turtles, the protection of which was sought by the 
measure at issue in that dispute. (Appellate  Body Report, US – Shrimp , para.  131) 
193 See also Panel Reports, para.  7.128 (quoting Mexico's second written sub mission to the Panels, 
para. 32). 
194 Panel Reports, para.  7.128 (referring to Mexico's response to Panel question No. 84, para. 130).  
195 Mexico's appellant's submission, para.  147. 
196 Mexico's appellant's submission, para.  148. 
197 Mexico's appellant's submissi on, para.  147. In Mexico's view, "[a]s expressed in the preamble of the 
WTO Agreement, the objective of every WTO Member is to act sustainably", and this objective must "inform 
the interpretation of the Article  2.1 of the TBT  Agreement". (Ibid., para.  149) 
198 Mexico's appellant's submission, para.  149. 
199 See para. 5.8 above.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the detrimental impact caused by the 2016 Tuna Measure stems exclusively from  a legitimate 
regulatory distinction in light of the objectives the United  States  chose to pursue through the 
measure. On the basis  of the above considerations, we do not need to examine whether, in the 
circumstances o f the present dispute, the 2016  Tuna M easure is incompatible with Article  2.1 
because it encourages the use of FADs and other forms of fishing that are unsustainable for tuna 
stock.  
6.27.   We now turn to examine what the legal standard under Article  2.1 of the TBT Agreement , as 
articulated  above, ent ails in the context of the present dispute, and whether the Panels erred in their 
articulation and application thereof.   
6.1.3   What the legal standard under Article  2.1 of the TBT Agreement  entails in this 
dispute  
6.28.   As noted in paragraph 6.3 above, the Panels cons idered that, in light of the specific 
circumstances of this dispute, their task in examining the parties' respective claims under Article  2.1 
was to ascertain "whether the relevant regulatory distinctions are appropriately 'calibrated' and 
'tailored' to, a nd commensurate with", the different risks to dolphins arising from the use of different 
fishing methods in different areas of the ocean .200 After establishing "the risk profiles of the relevant 
fishing methods in different areas of the ocean, taking into ac count data on both observable and 
unobservable harms"201, the Panels examined the relevant constituent elements of the 2016  Tuna 
Measure. They then synthesized their intermediate analyses "to reach an overall, holistic conclusion" 
regarding whether the labelling conditions under the m easure are calibrated to the relevant risk 
profiles.202 On this basis, the Panels ultimately found that the 2016 Tuna Measure is consistent with 
Article  2.1.203 
6.29.   On appeal,  Mexico claims that the Panels erred in their "legal interpret ation" of the calibration 
test under Article  2.1.204 We recall, however, that calibration is not a separate legal standard under 
Article  2.1 but, rather, a case -specific analytical tool used to assess whether the 2016 Tuna Measure 
is consistent with this provision. As explained above, we understand Mexico's arguments to concern 
whether, in applying the calibration analysis, the Panels prope rly assessed the nexus between the 
regulatory distinctions and the measure's objectives .205  
6.30.   Mexico argues in this regard that, in assessing the consistency of the 2016  Tuna Measure with 
Article  2.1, the Panels erred in determining that the measure is calibrated to the risks to dolphins 
arising from different fishing methods in different areas of the oceans, without at the same time 
considering whether the regulatory distinctions that the measure  draws are rationally rel ated to its 
objectives. In particular, Mexico contends that the Panels failed to consider risks relating to 
inaccurate labelling in examining the risk profiles of relevant fishing methods and ocean areas for 
the purpose of the calibration analysis. In Mexi co's view, because the 2016 Tuna Measure cannot 
achieve its objectives without label accuracy, a proper calibration analysis should have included 
considerations of such risks of inaccurate labelling.206 
6.31.   Mexico also alleges several errors in the Panels' "esta blishment and assessment of the risk 
profiles of different fishing methods in different ocean areas", which, in Mexico's view, "resulted in 
deficiencies that caused the Panels to subsequently err in conducting their assessment of whether 
the relevant regul atory distinctions [under the 2016 Tuna Measure] are calibrated".207 Specifically, 
Mexico claims that the Panels erred in assessing and comparing the risk profiles of different fishing 
methods without differentiating between different ocean areas.208 Mexico co ntends that, as a result, 
                                                
200 Panel Reports, para.  7.103 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.252).  
201 Panel Reports, paras.  7.149 and 7.525.  
202 Panel Reports, paras.  7.529 and 7.704.  
203 Panel Reports, para. 7.717.  
204 Mexico's appellant's submission, para.  78. 
205 See para. 6.16 above.  
206 Mexico's appellant's submission, paras.  99 and 117 -118. 
207 Mexico's appellant's submission, para.  154. 
208 Mexico's appellant's submis sion, paras.  159-172, 235 -240, and 254 -260. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the Panels' calibration analysis is deficient because it fails to examine whether the relevant 
regulatory distinctions under the measure are calibrated on a fishery -by-fishery basis.209  
6.32.   Addressing Mexico's arguments calls for us to  establish what a proper calibration analysis 
entails for the purpose of this dispute, before assessing  whether the Panels erred in their calibration 
analysis. Specifically, we address: (i)  how the objectives of the 2016  Tuna Measure, and the risk of 
inaccuracy of the dolphin -safe label, should be taken into account in a proper calibration analysis; 
and (ii) whether the Panels erred by limiting aspects of their calibration analysis to a comparison of 
the risk profiles of different fishing methods.210  
6.1.3.1   Whether  the Panels erred in failing to consider the nexus between the regulatory 
distinctions of the measure and its objectives  
6.33.   Mexico raises three interconnected arguments in support of its claim that the Panels failed to 
assess the nexus between the regulatory  distinctions of the measure and its objectives in their 
calibration analysis. Mexico argues that: (i)  the Panels' calibration analysis fail ed to recognize the 
relevance of label accuracy in light of the objectives of the 2016  Tuna Measure; (ii)  the Panels  failed 
to include risks of inaccuracy as part of the risk profiles of the different ocean areas to which the 
2016 Tuna Measure should be calibrated; and (iii)  by finding that the 2016 Tuna Measure 
contemplates a margin of error, the Panels erroneously con sidered that the measure tolerates label 
inaccuracy. We examine these arguments in turn.  
6.1.3.1.1   Whether the Panels' calibration analysis t ook into account the accuracy of the 
dolphin -safe label in light of the objectives of the 2016 Tuna Measure  
6.34.   Based on the App ellate  Body's findings in the first compliance proceedings, Mexico submits 
that a proper calibration analysis "must take into account the nexus between the regulatory 
distinctions and the objectives of the measure".211 In Mexico's view, "[c]onsideration of t he nexus 
between the detrimental impact and the objectives of the measure as a part of the 'calibration' test 
helps to ensure that a WTO Member 's regulatory space is respected without undermining the 
disciplines set forth in the TBT Agreement  and other WTO  Agreement s."212 Mexico argues that, 
"[a]s a consumer labelling measure", the 2016 Tuna Measure "cannot achieve [its] objectives 
without label accuracy" .213 For Mexico, a claim that the regulatory distinctions of the measure are 
"'calibrated' to the different risks posed to dolphins by different fishing methods in different ocean 
areas … cannot justify the detrimental impact on Mexican tuna products if the measure fails to ensure 
that the label provides accurate information to consumers" .214 Mexico thus alleges t hat the 
Panels'  calibration analysis was "narrow"215 and "incomplete"216 because the Panels failed to 
recognize the relevance of label accuracy to the calibration analysis . 
                                                
209 Mexico's appellant's submission, paras.  230-240, 252 -260, and 273 -274, and fn  207 to para.  166. 
210 We address the other specific errors alleged by Mexico regarding the Panels' assessment of risk 
profiles in sect ion 6.1.4, and whether the 2016 Tuna Measure is properly calibrated in section 6.1.5, below.  
211 Mexico's appellant's submission, para.  97 (quoting Appellate  Body Report, US – Tuna II (Mexico) 
(Article  21.5 – Mexico) , para.  7.155). In its appellant's submiss ion, Mexico argues that " both an examination of 
the nexus between the regulatory distinctions and the objectives of the measure and an examination of 
whether the measure is 'calibrated' are relevant factors for consideration in the assessment of whether th e 
2016 tuna measure is designed and applied in an even -handed manner." (Ibid., para.  98 (emphasis added)) 
This statement suggests that, in Mexico's view, consideration of the rational relationship may not be 
encompassed in the calibration analysis, such th at the Panels should have determined separately whether 
there is, indeed, a rational relationship between the regulatory distinctions of the 2016 Tuna Measure and its 
objectives. However, Mexico clarified at the hearing that, in order to be properly  calibr ated, the regulatory 
distinctions of the 2016 Tuna Measure would have to be rationally related to its objectives.  
212 Mexico's appellant's submission, para.  100. Mexico also indicated at the hearing that, for a measure 
to be properly calibrated, it must not be designed or applied in a manner that constitutes a means of arbitrary 
or unjustifiable discrimination, and the primary factor for examining whether the measure constitutes such 
discrimination is to assess whether the detrimental impact can be reconciled  with, or is rationally related to, 
the objectives of the measure.  
213 Mexico's appellant's submission, para. 99.  
214 Mexico's appellant's submission, para.  99. 
215 Mexico's appellant's submission, para.  116. 
216 Mexico's appellant's submission, para.  117. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.35.   The United  States  contends that Mexico  is wrong in claiming that the Panels erred in following 
the Appellate  Body's guidance in the previous compliance proceedings.217 The United  States  argues 
that the Appellate  Body clearly set out what it considered to be the appropriate calibration analysis  
by repeatedly referring to the risk profiles of different fishing methods in different areas of the ocean, 
and by indicating that those risk profiles should reflect the relative risks of observed and unobserved 
mortalities and injury.218 In the United  States ' view, the Panels correctly assessed the 
WTO-consistency of the 2016  Tuna Measure by considering whether its distinctions are calibrated to 
different risks to dolphins.  
6.36.   We begin by recalling the Appellate  Body's relevant findings in the original and first  
compliance proceedings regarding the calibration analysis in this dispute . We recall that  the 
United  States  sought to demonstrate that the detrimental impact under the original Tuna Measure 
stemmed exclusively from a legitimate regulatory distinction by i ntroducing the notion of 
calibration.219 As a result, the Appellate  Body used the notion of calibration as an analytical tool to 
assess the consistency of the original Tuna Measure under the second step of the analysis of 
"treatment no less favourable". However, the Appellate  Body found that the United  States  had not 
demonstrated that the original Tuna Measure was calibrated to the risks to dolphins .220 Rather, the 
Appellate  Body shared the original panel's view that, while the risks to dolphins arising fro m purse 
seine fishing by setting on dolphins  – a fishing method predominantly used by Mexican fleets – were 
fully addressed in the original Tuna Measure221, the risks to dolphins arising from the use of other 
fishing methods  – predominantly used by US and ot her fishing fleets – were not.222 In the original 
proceedings, the Appellate  Body thus accepted the premise that the original Tuna Measure would 
not violate Article  2.1 if it was properly calibrated to the risks to dolphins arising from the use of 
different fishing methods in different areas of the oceans.223 
6.37.   Referring to the original proceedings , the Appellate  Body indicated  in the first compliance 
proceedings  that it was therefore appropriate to conduct an analysis involving the following:  
[F]irst, an identif ication 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.224 
6.38.   The Appellate  Body further noted that "the reasoning set out in adopted Appellate  Body an d 
panel reports" provides guidance for WTO Members to bring their inconsistent measures into 
compliance with their obligations under the covered agreements.225 In light of the fact that the 
United  States  had defended its 2013  Tuna Measure under Article  2.1 in terms very similar to those 
used in the original proceedings, the Appellate  Body considered that the first  compliance panel's 
inquiry in those proceedings should have encompassed: (i)  an assessment of the "overall relative 
risks or levels of harm to dolphins" arising from different fishing methods in different ocean areas226; 
                                                
217 United States' appellee's submission, para.  47. 
218 United  States' appellee's submission, para.  48. According to the United  States, "at no time did the 
Appellate  Body ever suggest that the risk profiles reflect anything other than observed and unobserved 
mortalit y or injury to dolphins." (Ibid. (referring to Panel Reports, para.  7.108))  
219 See para. 6.12 above.  
220 Appellate  Body Report, US – Tuna II (Mexico) , para. 297. 
221 Appellate  Body Report, US – Tuna II (Mexico) , para.  287 (referring to Original Panel Report, 
para. 7.505).  
222 Appellate  Body Report, US – Tuna II (Mexico) , para.  292 (referring to Original Panel Report, 
para. 7.534 and fn  767 thereto).  
223 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.154 -7.155 (referring 
to Appellate  Body Report, US – Tuna II (Mexico) , para. 297).  
224 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.155.  
225 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.156.  
226 Appellate  Body Report, US – Tuna II  (Mexico) (Article  21.5 – Mexico) , paras.  7.252 and  7.353.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  and (ii)  an assessment as to whether the differences in the dolphin -safe labelling conditions under 
the measure are appropriately tailored to227, or commensurate with228, those respect ive risks.229 
6.39.   Thus, under the calibration analysis set out by the Appellate  Body in the original and first 
compliance proceedings, the risks to which the regulatory distinctions must be calibrated are risks 
to dolphins from the use of different fishing metho ds in different areas of the ocean. In our view, 
therefore, the Panels correctly considered that "the relevant inquiry is one that focuses on the risks 
that dolphins face as a result of the use, in different areas of the ocean, of different fishing 
methods ."230  
6.40.   Moreover, as the Appellate  Body found in the first compliance proceedings, the examination 
of whether the regulatory distinctions are commensurate with different risks to dolphins must be 
conducted "taking account of the objectives of the measure".231 Indeed, aspects of the 
Appellate  Body's reasoning as to why the first compliance panel erred in its application of Article  2.1 
illustrate how considerations of the 2013 Tuna M easure 's objectives, and the related issue of label 
accuracy, form part of the cal ibration analysis. Specifically, the Appellate  Body noted that the first 
compliance panel had dismissed the United  States ' argument that the different tracking and 
verification requirements are justified or explained in light of the higher degree of risk t o dolphins in 
the ETP large purse  seine fishery.232 According to the first compliance panel, the different risk profiles 
of different fisheries do not explain regulatory distinctions in the tracking and verification 
requirements because such distinctions are  triggered after the tuna has been caught.233 The 
Appellate  Body, however, disagreed with the first compliance panel's view that considerations of the 
similarities and differences in risks to dolphins were irrelevant to evaluating the even -handedness 
of the tracking and verification requirements . To the Appellate  Body, the first compliance panel's 
disregard of the "considerations of the similarities and differences in risks [to dolphins]" did not 
comport with its own reasoning that "the accuracy of the US dol phin-safe label can be compromised 
at any stage of the tuna production stage, in contradiction with the objectives of the amended tuna 
measure ".234  
6.41.   Thus, in the first compliance proceedings, th e Appellate  Body found  that the tracking and 
verification requirements should have been calibrated to the risks to dolphins arising from the 
different fishing methods in different areas of the ocean so as to avoid co mpromising the accuracy 
of the dolphin -safe label and contradi cting the measure's objectives.235 These findings confirm that 
considerations regarding label accuracy should have informed  the calibration analysis, precisely 
because the accuracy of the dolphin-safe label was directly relate d to the objectives of the 2013  Tuna 
Measure. Thus, considerations of the nexus between the regulatory distinctions and the measure's 
objectives, rather than being a separate inquiry, are encompassed in  a proper calibration analysis.  
                                                
227 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.163 and  7.252 -7.253.  
228 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.155, 7.160, 
and 7.252 -7.253.  
229 See e.g. Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.252.  
230 Panel Reports, para.  7.109.  
231 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.155.  
232 We recall that the Appellate  Body also found that the first compliance panel had not performed a 
proper analysis under Article  2.1 of the TBT  Agreement due to the following errors: (i)  the panel's segmented 
analysis of the 2013 Tuna Measure; (ii)  its erron eous assumption that disqualifying the method of setting on 
dolphins from the dolphin -safe label was found to be consistent with Article  2.1 of the TBT  Agreement in the 
original proceedings; (iii)  its failure to take due account of the different risks asso ciated with tuna fishing in 
different fisheries by focusing solely on unobserved  harms to dolphins; and (iv)  its focus on the technique of 
setting on dolphins in assessing the respective risk profiles of different fishing methods and areas of the ocean. 
(Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.126, 7.159, 7.161, and  7.165)  
233 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.142 (referring to 
Original Panel Report, para.  7.398).  
234 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.166. (Ibid., fn  611 to 
para. 7.166 (referring to First Compliance Panel Report, para.  7.233) (emphasis added)) The Appellate  Body 
also noted that the first  compliance panel had indicated th at the different tracking and verification 
requirements that apply outside the ETP large purse seine fisheries are less burdensome, making it more likely 
that tuna caught other than by ETP large purse seine vessels will be incorrectly labelled as dolphin -safe. (See 
also Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para. 7.253)  
235 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.166 and fn  611 
thereto, and para. 7.169.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.42.   Turning to the Panels' findings in these proceedings, the Panels recalled that the 
Appellate  Body's findings in the first compliance proceedings made clear that : 
[W]hile there may in theory be a number of ways in which a panel could assess the 
'even -handedness' of a measure challenged under Article  2.1 of the  TBT Agreement , in 
the specific context of these proceedings, the appropriate  legal standard for the Panels 
to apply is one that focuses on the relationship between the risks posed to dolphins by 
different fishing methods in different areas of the ocean, o n the one hand, and the 
relevant regulatory d istinctions, on the other hand.236  
Thus, the Panels understood their task to be that of ascertaining "whether the relevant regulatory 
distinctions are appropriately 'calibrated' and 'tailored' to, and commensurat e with, the different 
risks to dolphins arising in different fisheries."237 If the relevant regulatory distinctions are so 
calibrated , the Panels considered that this would indicate that the 2016 Tuna Measure is not 
inconsistent with Article  2.1. 
6.43.   The Panels found that, insofar as Mexico  considered that they should assess the existence of 
a rational relationship between the detrimental impact and the objectives of the 2016 Tuna Measure 
as a separate or distinct step in their analysis, such an approach was not supported by the 
Appellate  Body's reports in the original or the first compliance proceedings.238 In this regard, the 
Panels did not read the Appellate  Body's reports  as requiring, beyond calibration, "any additional, 
separate analysis" of the  relationship b etween the objectives of the measure and the detrimental 
impact.239 In our view, the Panels' statements comport with the Appellate  Body's findings, as 
reviewed in paragraphs  6.36-6.41 above , that considerations of the nexus between the regulatory 
distinction s and the measure's objectives, rather than being a separate inquiry, are an integral part 
of a proper calibration analysis.  
6.44.   To the Panels, the Appellate  Body's statement that the calibration analysis must be conducted 
"taking account of the measure's obje ctives" meant that those objectives must "inform the criteria 
in respect of which calibration is to be assessed", and that the Panels had to "bear in mind" those 
objectives in applying the calibration analysis to the facts of this dispute.240 The Panels reca lled that 
the objectives of the 2016 Tuna Measure are: (i) "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" ; and (ii) "ensuring th at consumers are not misled or deceived about 
whether tuna  products contain tuna that was caught in a manner that adversely affects dolphins".241 
Thus, the Panels considered that the 2016 Tuna Measure "aims to convey accurate information to 
consumers in orde r to ensure that the US tuna market is not used to encourage fishing fleets to 
catch tuna in a manner that adversely affects dolphins."242 In the Panels' view, calibration to the 
risks to dolphins arising from the use of different fishing methods in differen t areas of the ocean 
would take into account the objectives of the 2016 Tuna Measure.243 The Panels' findings correctly 
suggest that the design, structure, and expected operation of the tuna measure reveal that the 
measure seeks to achieve both its objective s in concert. We thus share the Panels' view that these 
objectives are "mutually complementary and reinforcing, and work together to 'address [the adverse 
effects of] fishing techniques on dolphins'".244  
6.45.   In this respect, we recall Mexico's argument that, "[ a]s a consumer labelling measure", the 
2016 Tuna Measure "cannot achieve [its] objectives without label accuracy", and that a claim that 
the regulatory distinctions of the measure are "'calibrated' to the different risks posed to dolphins 
by different fish ing methods in different ocean areas … cannot justify the detrimental impact on 
Mexican tuna products if the measure fails to ensure that the label provides accurate information to 
                                                
236 Panel Reports, para.  7.102.  
237 Panel  Reports, para.  7.103 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.252).  
238 Panel Reports, para.  7.115.  
239 Panel Reports, para.  7.115.  
240 Panel Reports, paras.  7.116 -7.117.  
241 Panel Reports, para.  7.117 (quoting Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.16).  
242 Panel Reports, para.  7.125 (referring to Original Panel Report, para.  7.427). (fn omitted)  
243 Panel Reports, para.  7.117.  
244 Panel Repor ts, para.  7.125 (quoting Original Panel Report, para.  7.550). Mexico agrees that the 
objectives of the measure are "inseparable". (Mexico's appellant's submission, para.  144) WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  consumers" .245 As discussed above, the Appellate  Body's findings in the first compliance proceedings 
indicate that considerations regarding label accuracy are encompassed in a proper  calibration 
analysis. Accordingly , we disagree that a calibration analysis, on the basis of risks to dolphins, would 
fail to a scertain whether the labels granted under the relevant labelling conditions are accurate and, 
as a consequence, whether the regulatory distinctions in such conditions are rationally related to the 
measure's objectives.  
6.46.   Instead, we consider that , where the  calibration analysis is conducted properly, taking account 
of the objectives pursued by the 2016 Tuna Measure, this exercise should also ascertain whether 
the label granted under the measure at issue convey s the information regarding the dolphin -safe 
nature of the tuna products to consumers.246 This is because, if the calibration analysis  shows that 
the strictness of the different labelling conditions is indeed commensurate with the risks of harms to 
dolphins, it indicate s that the labels granted under these  conditions w ould allow consumers to obtain 
information regarding whether the tuna in the tuna products is harvested in a manner that harms 
dolphins. Therefore, we agree with the Panels that a proper calibration to the risks to dolphins arising 
from the us e of different fishing methods in different areas of the ocean would take into account the 
objectives of the 2016 Tuna Measure247, and would help to ascertain the nexus between such 
objectives and the different labelling conditions under the measure. In the same vein, we also agree 
with the Panels that the existence of a rational relationship between the regulatory distinctions and 
the objectives of the 2016  Tuna Measure need not be assessed as a separate or distinct step  in their 
analysis.248  
6.1.3.1.2   Whether the risk s of label inaccuracy form part of the risks to which the 2016 
Tuna Measure must be calibrated  
6.47.   Mexico contends that the Panels erred in finding that calibration under Article  2.1 "requires a 
panel to simply 'bear in mind the objectives of the … Measure'".249 Rather, Mexico emphasizes that 
the objectives of the measure "must be reflected in the substantive criteria  for assessing whether 
the measure's regulatory distinctions are designed and applied in an even -handed manner, including 
on the basis of ' calibrati on'".250 As the 2016 Tuna Measure can only achieve its objectives through 
label accuracy251, such criteria must include factors relating to the risk of inaccurate labelling.252 
Thus, Mexico argues that the Panels erred in finding that, for the purpose of the calibration analysis, 
risks relating to inaccurate labelling are not part of the risk profiles of the different fishing methods 
and ocean areas. Mexico  submits that, in doing so, the Panels' approach "preclude[d] an assessment 
from taking full account of the particular circumstances of the case"253, and "did not give meaningful 
relevance" to the nexus between the detrimental impact caused by the regulatory distinctions and 
the objectives of the measure.254 
6.48.    The A ppellate  Body's findings reviewed above suppo rt Mexico's view that considerations 
regarding label accuracy are relevant to  assessing the nexus between the regulatory distinctions 
under the 2016 Tuna Measure and its policy objectives.255 However, the Appellate  Body did not 
suggest that the risk of label  inaccuracy constitutes a risk to which the relevant regulatory 
distinctions must be calibrated. Rather, as noted above, the Appellate  Body emphasized that the 
risks to which the regulatory distinctions must be calibrated were risks to dolphins arising fro m 
tuna fishing in different fisheries.256 Thus, while accuracy of the information conveyed to consumers 
through the dolphin -safe label is a consideration that should inform the calibration analysis , we share 
the Panels' view that this is "different from sayi ng that the applicable legal standard … requires the 
                                                
245 Mexico's appellant's submission, para.  99. (fn omitted)  
246 As noted in para. 5.1 1 above, under the 2016 Tuna Measure, tuna products labelled as dolphin -safe 
must not contain tuna harvested in a manner that adversely affects dolphins.  
247 See para. 5.8 above.  
248 Panel Reports, para.  7.115. In sections 6.1.4 and 6.1.5 below, we examine whe ther the Panels 
conducted the calibration analysis properly in this dispute.  
249 Mexico's appellant's submission, para.  138 (quoting Panel Reports, para.  7.118).  
250 Mexico's appellant's submission, para.  138. 
251 Mexico's appellant's submission, para.  99. 
252 See Mexico's appellant's submission, paras.  99, 114, and 124.  
253 Mexico's appellant's submission, para.  123. 
254 Mexico's appellant's submission, para.  127. 
255 See paras. 6.36 -6.41 above. See also Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico), para.  7.166 and fn  611 thereto (referring to First Compliance Panel Report, 
para. 7.398).  
256 See e.g. Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.155.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Panels to determine whether the 2016 Tuna Measure is calibrated, inter alia , to the risk of inaccurate 
dolphin -safe information being passed to consumers ".257 
6.49.   Mexico additionally argues that, in finding that risk profiles of different fisheries do not 
encompass risks of label inaccuracy258, the Panels failed to recognize that the risks to dolphins "are 
inextricably linked to the characteristics of ocean areas and fisheries that impact the accuracy of the 
dolphin-safe label".259 Specifically, "[f]or a given fishing method capable of causing harms to 
dolphins, dolphins will be at a greater relative risk of harms from that fishing method in ocean areas 
that are unregulated or that have insufficient regulatory ove rsight, resulting in unreliable reporting, 
significant [illegal, unreported , and unregulated] IUU fishing, and/or significant transshipment at 
sea, than in ocean areas that have sufficient regulatory oversight and reliable reporting."260 
In Mexico's view, fo r tuna caught in such ocean areas, "stricter certification requirements and 
tracking and verification requirements are justified (and required) on the basis that they are 
calibrated to the higher relative risks of harms to dolphins".261 Mexico therefore contends that the 
Panels erroneously focused the calibration assessment solely on the impact of fishing methods in 
terms of their harm to dolphins, and that such an approach is "incomplete " and  "legally 
erroneous".262 
6.50.   The United  States  contends that "Mexico makes a new factual allegation not made (or 
supported) before the Panels", namely, that "'the reliability of applicable systems' is 'inextricably 
linked' with actual, physical harm to dolphins"263, and that dolphins will therefore be at a g reater 
risk of harms in unregulated or insufficiently regulated ocean areas, resulting in unreliable reporting, 
significant IUU fi shing, and/or significant trans -shipment at sea, than in sufficiently regulated ocean 
areas.264 The United  States  points out tha t Mexico never provided any evidence to the Panels of a 
link between the risks of harm to dolphins, on the one hand, and the low reliability of applicable 
systems, on the other hand.265 The United  States  highlights that "Mexico never even argued this 
point b efore the Panels – and the Panels made no such finding of fact."266 
6.51.   By arguing that "dolphins will be at a greater relative risk of harms from [a  given ] fishing 
method in ocean areas that are unregulated or that have insufficient regulatory oversight, result ing 
in unreliable reporting, significant IUU fishing, and/or significant transshipment at sea"267, we 
understand Mexico to suggest that tuna fishing in ocean areas with less reliable regulatory systems 
is more likely to lead to "actual, physical harm to dolp hins".268 However, Mexico has not 
substantiated such an assertion. In these circumstances, we see no reason to disagree with the 
Panels' statement that "the risks of inaccurate certification, reporting, and/or record -keeping are not 
risks that affect dolphin s themselves", or "risks that arise from the use of different fishing methods 
in different areas of the ocean".269 
6.52.   At the same time, we emphasize that issues regarding label inaccuracy are relevant to 
assessing whether the labelling conditions under the meas ure are properly calibrated. As the Panels 
also acknowledged, the risks of inaccurate certification, reporting, and/or record -keeping may "have 
an indirect influence on the extent to which different fishing methods are used to catch tuna intended 
for the U S market" .270 Furthermore, the Panel s recognized that "fish caught in different areas of the 
ocean through the use of different fishing methods may be associated with a greater or smaller risk 
                                                
257 Panel Reports, para.  7.112.  
258 Panel Reports, para. 7.112.  
259 Mexico's appellant's submission, para.  124. 
260 Mexico's appellant's submission, para.  109. 
261 Mexico's appellant's submission, para.  110. 
262 Mexico's appellant's submission, para.  124. 
263 United  States' appellee's submission, para.  45 (quoting Mexico's appella nt's submission, para.  124).  
264 United  States' appellee's submission, para.  45 (quoting Mexico's appellant's submission, para.  109).  
265 United  States' appellee's submission, para.  53. 
266 United  States' appellee's submission, para.  53 (referring to Panel Repor ts, para.  7.110).  
267 Mexico's appellant's submission, para.  109. 
268 United  States' appellee's submission, para.  45 (referring to Mexico's appellant's submission, 
paras.  120 and 124).  
269 Panel Reports, para.  7.110. (emphasis added)  
270 Panel Reports, para.  7.110 . This is because "one of the objectives of the label is to provide 
consumers with information as to the dolphin -safe status of tuna products in order to  ensure 'that the 
US market is not used to encourage fishing fleets to catch tuna in a manner that adversely affects dolphins'." 
(Panel Reports, fn  222 to para.  7.110 (quoting Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  6.3)) WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  of inaccurate labelling depending on a range of interconnected fa ctors, including the persons involved 
in the catch, available technology, and applicable domestic and international regulatory 
requirements."271 To the Panels, these risks were "relevant"272, and even "central", to their 
application of the calibration analysis , precisely because , in doing so, they were required to take the 
objectives of the measure into account.273 We therefore consider that the Panels did not, as Mexico 
contends, adopt an approach to calibration that is "narrow" and "incomplete".274  
6.53.   Furthermore, by noting that the risk of inaccuracy depends on a range of interconnected 
factors, including "the persons involved in the catch, available technology, and applicable domestic 
and international regulatory requirements"275, the Panels expressly recognized tha t the risk of 
inaccuracy  encompasses the factors leading to such inaccuracy. Indeed, as the Panels explained, 
the expression "risk of inaccuracy" means "the risk that  an error  in the recording and reporting of 
information somewhere in the catch and processing chain  could result in a batch of t una being 
designated as dolphin -safe while in fact containing tuna that sho uld have been designated as 
non-dolphin -safe."276 Our review of the Panels' findings therefore does not support Mexico's 
argument that th e Panels erred in defining the risk of inaccuracy  "narrowly to relate to the symptom 
or outcome (i.e.  an inaccurate label) rather than the risk factors that cause such an outcome".277  
6.1.3.1.3   Whether the Panels erred in  referring to "margin of error"  in their calibr ation 
analysis  
6.54.   Mexico also takes issue with the Panels' discussion of the margin of error in the context of 
their analysis regarding risks of inaccuracy. Mexico disagrees with the Panels that the existence of 
margins of error in the certification and track ing and verification requirements is not necessarily 
inconsistent with the objectives of the measure.278 Rather, Mexico contends that "the measure does 
not contemplate a 'margin of error' or a tolerance threshold for inaccurate labelling, and it does not 
incorporate a de minimis  test for accuracy."279 Mexico also argues that the Panels erroneously "took 
the position that fisheries that have lower risk profiles … will always have a lower risk of conveying 
incorrect information to consumers", and that, by doing s o, "determined that allowing inaccurate 
labels is consistent wit h the objectives of the measure ".280 
6.55.   The United  States  contends that Mexico's argument is based on a fundamental 
misunderstanding of the Panels' analysis to the extent that it suggests that the Panels'  approach is 
driven to tolerate less accurate labelling for tuna products from outside the ETP  large purse  seine 
fisheries.281 In the United  States ' view, the Panels properly recognized that the risk of inaccurate 
labelling is not a constant282, and that "the  U.S. measure need not 'be completely error -proof in 
order to be calibrated' (and, thus consistent with Article  2.1)."283 Rather, the Panels correctly 
indicated that "the more pertinent question is whether the possibility  of error is tailored to, or  
commensurate with, the different risks to dolphins arising from the use of different fishing methods 
in different areas of the ocean."284 Therefore, the United  States  argues that the Panels did not err in 
relying on the concept of margin of error in discuss ing the certification and tracking and verification 
requirements, and that this concept is entirely consistent with the guidance provided by the 
Appellate  Body in both the original proceedings and the first  compliance proceedings.285 
                                                
271 Panel Reports, para.  7.110.  
272 Panel Reports, para.  7.113.  
273 Panel Reports, para.  7.118.  
274 Mexico's appellant's submission, para.  124. 
275 Panel Reports, para.  7.110. (fn omitted)  
276 Panel Reports, para.  7.119. (emphasis added)  
277 Mexico's appellant's submi ssion, para.  139. 
278 Mexico's appellant's submission, para.  133 (referring to Panel Reports, para.  7.122).  
279 Mexico's appellant's submission, para.  140. 
280 Mexico's appellant's submission, para.  135. 
281 United  States' appellee's submission, para.  66. 
282 United  States' appellee's submission, para.  68. 
283 United  States' appellee's submission, para.  74 and fn 168 thereto (quoting Panel Reports, 
paras.  7.601 and 7.605).  
284 United  States' appellee's submission, para.  74 (quoting Panel Reports, para.  7.605). (emphasis 
added)  
285 United  States' appellee's submission, para.  75. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.56.   In our view, by equating  "margin of error" with "a tolerance threshold of inaccurate 
labelling"286, Mexico's above arguments are based on its understanding of the term "margin of error" 
as being synonymous with the ultimate inaccuracy of a dolphin -safe label. However, the 
Panels'  discussion of "margin of error", when read in its totality, suggests that the Panels did not 
equate the term with label inaccuracy. Rather, we understand the Panels' reference to the term 
"margin of error" as relating to the different degrees of strictness of the certification and tracking 
and verification requirements under the 2016 Tuna Measure. Pursuant to this understanding, the 
ultimate accuracy of the label depends not only on the different degrees of the strictness of the 
relevant requirements, but al so on the level of risks to dolphins in a given fishery to which these 
requirements apply.  
6.57.   We recall that the Panels introduced the notion of margin of error in discussing the "risk of 
inaccuracy".287 To this effect, the Panels indicated that "the existence  of a margin of error in 
certification, and tracking and verification requirements does not necessarily equate or give rise to 
a risk that the information ultimately conveyed to a consumer by a dolphin -safe label will itself be 
incorrect."288 Rather, to the Panels, "the risk of inaccurate information being passed to consumers 
by the label will depend not only on the referred margin of error, but also, and importantly, on the 
extent of events that require recording whether a dolphin mortality or serious injury  was observed 
in a given fishery."289 The Panels explained that the risk profile of relevant fisheries "is a good proxy 
to measure the extent of [such] events that require recording".290 Therefore,  the Panels reasoned 
that "in applying the calibration test, it  is appropriate … to consider whether the certification, and 
tracking and verification requirements applied in different fisheries are commensurate with, and 
tailored to, the particular risk profiles of those fisheries."291 More specifically:  
[I]n a fishery  where the risks to dolphins are low, it may be calibrated to apply 
certification, and tracking and verification requirements that tolerate a higher margin of 
error than the certification, reporting, and/or record -keeping requirements that apply 
in respect  of fisheries with a high risk profile. This is be cause the risk that the 
dolphin -safe label will communicate inaccurate information is a function of numerous 
factors, including not only the regulations in place, but also the different levels of dolphin 
interaction, mortality, and serious injury in different fisheries. Thus, in fisheries with 
high dolphin interactions and harms, more sensitive certification , and tracking and 
verification requirements may be needed to ensure the u ltimate accuracy of the 
dolphin -safe label, whereas in fisheries with low dolphin interactions and harms, less 
sensitive requirements  may be sufficient .292 
6.58.   Thus, the Panels' findings as set forth above indicate that the term "margin of error" relate s 
to the strictness of the releva nt certification and tracking and verification requirements, such that 
the less sensitive they are, the more likely that adverse effects on dolphins might go undetected 
and unreported. This, however, does not automatically translate into inaccuracy of the ultimate 
dolphin -safe label. Rather, as the Panels' statements quoted above make clear, the accuracy of the 
ultimate label depends not only on the sensitivity of the labelling conditions, but also on the level of 
risks to dolphins in a fishery. Where such risks are higher, the corresponding labelling conditions 
may need to be more "sensitive"293, or strict, to ensure the accuracy of the label in conveying the 
                                                
286 Mexico's appellant's submission, para.  140. 
287 As noted above, the Panels defined the "risk of inaccuracy" as the risk that, due to "an error in the 
recording and reporting of information", a batch of tuna containing tuna that should have been designated as 
non-dolphin -safe is nonetheless designated as dolphin -safe. (Panel Reports, para.  7.119)  
288 Panel Reports, para.  7.120.  
289 Panel Reports, para.  7.120. (emphasis added) The Panels indicated that, for  example, where the 
margin of error is high but the occurrence of such events is low in a given fishery, the risk of inaccurate 
information being conveyed to consumers would be low. Conversely, where the margin of error is low but 
occurrence of such events  is high, the resulting risk of inaccurate information would be high. (Ibid., 
para. 7.121) The Panels further explained that the "events that require recording" include "not only the events, 
such as death or serious injury of dolphins, which make up the ri sk profile of the relevant fishery, but also 
other events, such as the fact that dolphins were observed by the vessel captain or independent observer; 
whether or not dolphin -safe and non -dolphin -safe tuna were segregated in the wells on board the vessel; a nd 
whether that segregation was maintained during the trans -shipment and unloading of the tuna". (Ibid., fn  235 
to para.  7.121)  
290 Panel Reports, para.  7.121. (fn omitted)  
291 Panel Reports, para.  7.123.  
292 Panel Reports, para.  7.123. (emphasis added)  
293 Panel Reports, para.  7.123.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  information regarding the dolphin -safe nature of the tuna products. Conversely, where such risks 
are lower, less sensitive labelling conditions may be sufficient to ensure accuracy. Thus, we 
understand the Panels to have meant that the sensitivity of the labelling conditions should 
correspond, or be calibrated, to the risks to dolphins arising from the us e of different fishing methods 
in different areas of the ocean, so as to ensure accurate labelling.  
6.59.   We thus disagree with Mexico's contention that the Panels erroneously "took the position that 
fisheries that have lower risk profiles … will always have a lower risk of conveying incorrect 
information to consumers", and t hat, by doing so, "determined that allowing inaccurate labels is 
consistent with the objectives of the measure" .294 In our view, Mexico's argument conflates the 
strictness of the relevant labe lling conditions with the inaccuracy of the ultimate dolphin -safe label.  
While the term "margin of error", read in isolation, may be understood in the sense Mexico suggests, 
our above analysis indicates that the Panels used this term to denote the possibil ity of error as a 
result of different levels of strictness in the certification and tracking and verification  requirements, 
and did not equate it to the accuracy of the ultimate label. Rather, the latter depends not only on 
the sensitivity of the labelling  conditions but also, importantly, on the risks to dolphins arising from 
the use of different fishing methods in different areas of the ocean.  
6.60.   This being said, we do not consider that a reference to the term "margin of error" was 
necessary to the Panels' a ssessment of whether the 2016 Tuna Measure is properly  calibrated.295 
Indeed, the Panels highlighted that the question whether margins of error in the certification and 
tracking and verification requirements are consistent with the objectives of the measure "cannot be 
answered by looking at the regulations in isolation" but must be assessed "in the light of the relevant 
risk profiles in different fisheries".296 Read in its totality, the Panels' discussion rightly focused on 
the question whether the relevant reg ulatory distinctions are properly calibrated to the risks to 
dolphins.  
6.1.3.2   Whether the Panels erred by limiting aspects of their calibration analysis to a 
comparison of the risk profiles of different fishing methods  
6.61.   Mexico argues that the Panels erred in asses sing and comparing the risk profiles of different 
fishing methods without distinguishing between different ocean areas.297 Mexico considers that, in 
order to assess whether the measure is properly calibrated to the risks to dolphins, the Panels were 
required  to examine whether the 2016 Tuna Measure makes all relevant regulatory distinctions on 
the basis of both fishing methods and ocean areas.298 This is because, according to Mexico, risks to 
dolphins depend not only on the fishing methods used but also  on the relevant characteristics of the 
ocean areas where those fishing methods are used.299 Mexico considers this view to be supported 
                                                
294 Mexico's appellant's submission, para.  135. 
295 Indeed, we observe that certain statements by the Panels regarding the term "margin of error", 
when read in isolation, could potentially give rise to the understanding Mexico suggests. S pecifically, the Panels 
stated that "a measure that tolerates a larger margin of error where a risk is low, but tolerates a lower margin 
of error where the risk is high, may very well be calibrated." (Panel Reports, para.  7.606) To the extent "a 
larger mar gin of error" in this statement could be read to suggest a higher degree of label inaccuracy, this 
would be contradicted by other statements by the Panels and the totality of their calibration analysis.  
296 Panel Reports, para.  7.123.  
297 Mexico's appellant's submission, paras.  159-172. 
298 Mexico's appellant's submission, para.  166 and fn 207 thereto. In Mexico's view, fisheries "with 
relatively higher risk profiles" must be distinguished from fisheries with "relatively lower risk profiles", and 
should be inelig ible for the label. (Ibid., para.  167) Mexico refers to certain gillnet, longline, and trawl fisheries 
that the Panels found to have particularly high -risk profiles, and argues that "[p]ermitting access to the label to 
tuna caught by such methods in those ocean areas contradicts and undermines the objective of the tuna 
measure to discourage fishing practices that adversely affect dolphins." (Ibid., para.  167) 
299 Mexico's response to questioning at the hearing. The Appellate  Body in the first compliance 
proce edings explained that "[f]or 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." (Appellate 
Body Report, US – Tuna II (Mexico) (Artic le 21.5 – Mexico) , fn 130 to para.  6.10)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  by the Appellate  Body's articulation of the calibration analysis in previous proceedings in this dispute, 
as well as the "design, architecture, and revealing structure of the measure".300  
6.62.   The United  States  argues that the eligibility criteria relevant to this dispute draw distinctions 
on a fishing -method -by-fishing -method basis, and that it has not been suggested in any of the 
previou s proceedings in this di spute, by panels, the Appellate  Body, or Mexico, that addressing 
eligibility  on a fishing -method -by-fishing -method basis is inconsistent with Article  2.1 of the 
TBT Agreement .301 The United  States  considers that Mexico has not explained why this type of 
distinction is not permitted under Article  2.1 of the TBT  Agreement .302 In particular, the 
United  States  explains that, in the first compliance proceedings, the Appellate  Body did not reverse 
the pane l's findings on the basis that the panel had failed to make findings on a fishery -by-fishery 
basis with respect to  the eligibility criteria.303 The United  States  also highlights that Mexico's 
approach would render the determination provisions redundant.304  
6.63.   We note at the outset that what Mexico considers is required of the 2016 Tuna Measure, in 
order for it to be consistent with Article  2.1 is based at least in part on the Appellate  Body's 
statement that the dolphin -safe labelling 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 ".305 The Appellate  Body also explained that applying the calibration analysis entails an 
"identification of whether differ ent tuna fishing methods in different areas of the oceans pose 
different risks to dolphins" and examining whether, in light of these risks, "the different treatment 
created by the relevant re gulatory distinction shows that , as between different groups, the treatment 
accorded to each group is commensurate with the relevant risks ."306 However, t hese statements do 
not prescribe  that the regulatory distinctions under the 2016 Tuna Measure must be drawn on the 
basis of different ocean areas in order for the measure to be consistent with Article  2.1. Rather, the 
foregoing guidance by the Appellate  Body acknowledges that the risks to dolphins may differ across 
different ocean areas and that, in con ducting an assessment of risks to dolphins for the purpose of 
assessing whether the regulatory distinctions under the measure are indeed calibrated to different 
risks to dolphins, it is necessary to assess the risks across all relevant ocean areas in which  a 
particular fishing method is practi sed (i.e. individual fisheries) .  
6.64.   The essential question before the Panels was whether the relevant regulatory distinctions 
under the measure are calibrated to different risks to dolphins. The nature of this analysis ( i.e. how 
the Panels were required to apply the calibration analysis) is informed by the nature of the regulatory 
distinctions made under the measure itself. In this respect, we recall that, in determining whether 
detrimental impact 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."307 It is therefore useful to briefly recall certain features of the measure for the purpose of 
assessing Mexico's arguments.  
6.65.   The 2016 Tuna Measure makes several sets of  distinctions between different tuna products. 
In terms of the eligibility criteri a, the mea sure distinguishes between: (i)  tuna products containing 
                                                
300 Mexico's appellant's submission, para.  166 and fn  207 thereto. Mexico highlights that tuna caught by 
driftnet fishing on the high seas is ineligible for the dolphin -safe label and argues on this basis that the 
measure, in setting out the eligibility criteria, makes distinctions involving both fishing methods and ocean 
areas. In response to questioning at the hearing, Mexico stated that the design of the measure is subject to the 
legal analysis; so even if the eligi bility requirement was assessed under the measure on a fishing -method -by-
fishing -method basis, that would not shield it from challenge and it would not shield the measure from being 
assessed for calibration on a fishery -by-fishery basis.  
301 United  States' a ppellee's submission, paras.  117-118. 
302 United  States' appellee's submission, para. 118.  
303 United  States' appellee's submission, paras.  122-123. 
304 United  States' appellee's submission, para.  119. The United  States explains that, since the 
determination pro visions increase the certification and tracking and verification requirements in specific 
high-risk fisheries, the determination provisions would be "meaningless" if such high -risk fisheries were in any 
event ineligible for the label.  
305 Appellate  Body Repo rt, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para. 7.155. (emphasis added) 
See also Mexico's appellant's submission, para.  159. 
306 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para. 7.155. (emphasis added)  
307 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.31 (referring to  
Appellate  Body Report,  US – Clove Cigarettes , para.  182). See also Appellate  Body Reports, US – Clove 
Cigarettes , para.  215; US – COOL , para.  340; US – Tuna II (Mexico) , paras.  216 and 225.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  tuna caught by setting on dolphins or caught by driftnet fis hing on the high seas; and 
(ii) tuna products containing tuna caught by other fishing methods.308 While the former are 
automaticall y ineligible for the dolphin -safe label, the latter are eligible for the label subject to certain 
certification and tracking and verification requirements. Such certification and tracking and 
verification requir ements distinguish between: (i)  tuna products  containing tuna caught in the ETP 
large purse seine fishery; and (ii)  tuna products containing tuna caught in all other fisheries.309 Thus, 
at the level of the eligibility  criteria, the 2016 Tuna Measure draws a distinction on the basis of 
fishing  methods  insofar as the ineligibility of tuna caught by setting on dolphins is concerned.310 
Furthermore, at the level of the certification and tracking and veri fication requirements, the 
2016 Tuna Measure makes a distinction on the basis of different fisheries (i.e. the use of a particular 
fishing method in a particular ocean area).311 Specifically, these requirements distinguish between 
tuna products containing tuna caught in the ETP  large purse seine fishery and tuna products 
containing tuna caught in all other fisher ies.312 In order for a tuna  product to receive the dolphin -safe 
label, it must satisfy all of these requirements (in other words, the tuna must have been caught 
using an eligible fishing method, and it must have been certified, as well as tracked and verifie d, in 
accordance with the relevant requirements applicable to the fishery in which the tuna was caught).  
6.66.   Turning to the relevant findings by the Panels, we recall that the parties do not contest on 
appeal the Panels' finding that the 2016 Tuna Measure has  a detrimental impact on Mexican tuna 
products. In this regard, the Panels highlighted the Appellate  Body's finding in the first compliance 
proceedings that "'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'".313 
The Panels noted that "the 2016 Tuna Measure maintains the overall architectu re and structure of 
the original and 2013 Tuna Measures", including "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" .314 The Panels consider ed that, in light of the unchanged factual situation, 
"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 
2016 Tuna  Measure, similar to the original and the 2013 Tuna Measure, modifies the conditions of 
competition to the detriment of Mexican tuna products in the US market."315  
6.67.   The Panels proceeded to examine whether this detrimental impact stems exclusively from a 
legitimate regulatory distinction. The Panels began by assessing the evidence before them 
concerning the use of all relevant fishing methods in different areas of the ocean (i.e. fisheries)316 
before arriving at an overall conclusion regarding the risk profile o f each fishing method. Following 
their examination of the relevant risk profiles, the Panels considered it appropriate to examine 
"whether each of the elements of the measure is calibrated to the risks to dolphins arising from the 
use of different fishing methods in different areas of the ocean, and then synthesizing [their] 
intermediate analyses to reach an overall, holistic conclusion about the WTO -consistency of the 
Measure".317 For the purpose of assessing whether the eligibility criteria are properly cal ibrated, the 
Panels compared the risk profile of setting on dolphins  with the risk profiles of other fishing 
methods.318 By contrast, in examining the certification and tracking and verification requirements, 
the Panels compared the risk profiles of the rele vant fisheries (i.e. fishing methods and  ocean areas) 
with respect to which the 2016 Tuna Measure draws a distinction, namely, the ETP  large purse seine 
                                                
308 See paras. 5.10-5.11 above.  
309 See paras. 5.12 -5.13 and 5.17 above.  
310 Panel Reports, para.  7.568.  
311 See Panel Reports, para.  7.568.  As explained above, for the purpose 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 supra , fn 299.  
312 See Panel Reports, para.  7.568. We also note that, s ince tuna products containing tuna caught by 
driftnet fishing on the high s eas are ineligible for the dolphin -safe label, any certification (or tracking and 
verification) of tuna caught by driftnet fishing on the high seas would only have the effect that such tuna 
products would not  receive the dolphin -safe label.  
313 Panel Reports, para . 7.76 (quoting Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.236, in turn quoting Original Panel Report, para.  7.317).  
314 Panel Reports, para.  7.77. 
315 Panel Reports, para.  7.78. 
316 To the extent that Mexico argu es that the Panels failed to take into account all the relevant evidence 
in making this assessment, we address these arguments in section 6.1.4 below.  
317 Panel Reports, para.  7.529.  
318 See Panel Reports, paras.  7.539 -7.546.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  fishery and all other fisheries.319 The Panels explained that, "unlike the eligibility requirements, the 
certification requirements (and the tracking and verification requirements ) … draw distinctions on 
the basis of different fisheries, rather than different fishing methods."320  
6.68.   As explained above, Mexico contends that the Panels erred by comparing the risk p rofiles of 
different fishing methods, and not of individual fisheries.321 As indicated, in the context of assessing 
the certification  and tracking  and verification  requirements, the Panels compared the risk profiles of 
different fisheries. Since that approac h appears consistent with Mexico's preferred approach, we 
understand that this aspect of Mexico's arguments pertains specifically to the Panels' assessment of 
the eligibility criteria, with respect to  which the Panels compared the risk profiles of fishing methods, 
but not of individual fisheries.322  
6.69.    In this regard, Mexico argues that the Panels' approach is "incorrect" because the eligibility 
criteria under the measure "clearly distinguish based on method and area".323 Mexico considers that 
this is illustrate d by the fact that tuna caught by driftnet fishing on the high seas is also ineligible 
for the dolphin -safe label.324  
6.70.   We note that the distinction under the eligibility criteria between driftnet fishing on the high 
seas and other fisheries is indeed on the basis of both fishing method and ocean area.325 However, 
we recall that the second step of the "less favourable treatme nt" analysis under Article  2.1 
"focusses on the regulatory distinction(s) causing the detrimental impact on imported products".326 
Our above review of the Panels' findings and the Appellate  Body's findings in the first compliance 
proceedings indicate s that t he relevant regulatory distinctions giving rise to the detrimental impact 
in this dispute do not concern driftnet fishing on the high seas. Mexico has not demonstrated how 
the treatment under the measure of driftnet fishing on the high seas is related to t he Panels' findings 
of detrimental impact.327 Furthermore, one of the regulatory distinctions c ausing the detrimental 
impact on  Mexican tuna products is that tuna  products containing tuna  caught by setting on dolphins 
are ineligible  for the dolphin -safe labe l, while tuna products containing tuna caught by other fishing 
methods  are provisionally  eligible for the label.328 As noted above, the distinction underlying the 
ineligibility of tuna caught by setting on dolphins  is made on the basis  of fishing method, wit hout 
reference to any particular ocean area or fishery.  In our view, therefore, the fact that the measure 
at issue also disqualifies from the dolphin -safe label tuna products containing tuna caught by driftnet 
fishing on the high seas does not, in itself, undermine the Panels' approach in assessing, inter alia, 
whether the distinction between setting on dolphins and other fishing methods is calibrated to 
different risks to dolphins.  
6.71.   Mexico nonetheless argues that, "[e]ven if the measure did not apply the el igibility criteria on 
an ocean area basis, legally the calibration assessment must be undertaken on a fishing method and 
ocean area basis and, in certain circumstances, requires that the measure apply the eligibility criteria 
                                                
319 See Panel Reports, paras.  7.568 -7.573, 7.578, 7.599 -7.603, 7.613, 7.651 -7.652, 7.671 -7.673, 
and 7.709 -7.716.  
320 Panel Reports, para.  7.568.  
321 See para. 6.61 above.  
322 We are aware of Mexico's view that the Panels unduly focused on fishing methods in conducting their 
assessment  of risk profiles, such that the Panels failed to adequately assess the risks in each individual fishery. 
(See paras. 6.91 and 6.100 below) Since that aspect of Mexico's arguments relates more specifically to the 
way in which the Panels conducted their ass essment of risk profiles, we address it in section 6.1.4 below, 
rather than this section, which concerns more broadly whether the Panels correctly framed the calibration 
analysis.  
323 Mexico's appellant's submission, fn  207 to para. 166.  
324 Mexico's appellant 's submission, fn  207 to para. 166.  
325 See paras. 5.10 -5.11 above.  
326 Appellate  Body Reports, US – COOL (Article  21.5 – Canada and Mexico) , para.  5.93. See also 
Appellate  Body Report, US – Tuna II (Mexico) , para.  286. 
327 We note that, on appeal, Mexico only r aises the measure's distinct treatment of driftnet fishing on 
the high seas in support of its view that the Panels erred by making a fishing -method -by-fishing -method 
analysis. Mexico does not argue in its appellant's submission that: (a) the distinction be tween driftnet fishing 
on the high seas and other individual fisheries causes the detrimental impact on Mexican tuna products; or  
(b) the Panels erred by failing to examine whether this particular distinction is calibrated to different risks to 
dolphins.  
328 Panel Reports, paras.  7.76-7.78; Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.236; Original Panel Report, para.  7.317.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  on an ocean area basis in orde r to be in compliance with Article  2.1."329 In Mexico's view, because 
risks to dolphins depend not only on fishing methods but also on the characteristics of the ocean 
areas in which those fishing methods are used, eligibility criteria that are based solely on a distinction 
between different fishing methods (without identifying specific ocean areas in which those methods 
are used) would undermine the measure's objective of protecting dolphins from the risks of tuna 
fishing. As Mexico further explained at the hearing, in its view , the distinction between setting on 
dolphins and other fishing methods is per se inconsistent with Article  2.1, in light of the objectives 
of the measure, the manner in which the Appellate  Body has previously articulated the calibration 
analysis, and the fact that certain fisheries may have a risk profile equivalent to that of setting on 
dolphins in the ETP.  
6.72.   We recall that, under the second step of the "less favourable treatment" analysis under 
Article  2.1 of the TBT Agreement , the relevant question is whether the detrimental impact caused 
by the measure at issue  stems exclusively from a legitimate regulatory d istinction.330 In our view, 
in order to answer this question , it is necessary  to examine the distinction that gives rise to the 
detrimental impact. As indicated above, the detrimental impact in this dispute results, in part, from 
the distinction under the el igibility criteria between setting on dolphins and other fishing methods. 
Consequently, the test of whether the measure is even -handed requires assessing, inter alia331, 
whether this distinction is a legitimate regulatory distinction.  
6.73.   Furthermore, in this dispute, the Appellate  Body has accepted the premise that the Tuna 
Measure would not violate Article  2.1 if the relevant regulatory distinctions leading to detrimental 
impact are properly "calibrated" to the risks to dolphins arising f rom different fishing methods in 
different areas of the oceans.332 Thus, to the extent that Mexico's argument suggests that the 
distinction between setting on dolphins and other fishing methods is not even -handed simply 
because it is drawn  on the basis of fi shing methods, we do not consider Mexico's approach to be 
consistent with the findings from the original and first compliance proceedings. To the contrary, 
whether this distinction is legitimate for the purpose of Article  2.1 must be assessed through a 
comparison of the risk profiles of these different fishing methods.  
6.74.   In response to questioning at the hearing, Mexico  argued that a fishing -method -by-fishing -
method distinction for the purpose of the eligibility criteria would undermine the measure's objectiv e 
of protecting dolphins from the risks of tuna fishing.333 We recall, however, that the Appellate  Body 
has accepted that if it is shown that the regulatory distinctions under the measure are calibrated to  
different risks to dolphins, then the detrimental im pact under the measure would stem exclusively 
from a legitimate regulatory distinction.334 This approach by the Appellate  Body reflected the 
understanding that, given the design and structure of the Tuna Measure (including the distinction 
between setting on dolphins and other fishing methods), if it can be shown that the distinctions are 
calibrated to different risks to dolphins, this would also indicate that such distinctions are rationally 
related to, and hence capable of contributing to, the measure's obje ctives (including the objective 
of protecting dolphins). Indeed, as discussed in  section 6.1.3.1.1 above, we consider that the 
calibration analysis as set out by the Appellate  Body encompasses considerations of the nexus 
between the regulatory distinctions under the measure and the measure's objective. However, under 
Mexico's approach, the 2016 Tuna Mea sure would be per se inconsistent with Article  2.1, solely on 
the basis that such a distinction would undermine the objective of  protecting dolphins. In our view, 
Mexico has not demonstrated why a distinction on the basis of fishing methods would undermine  
the objective of protecting dolphins.  
                                                
329 Mexico's appellant's submission, fn  207 to para.  166. 
330 See para. 6.9 above.  
331 As part of this assessment, the Panels were also required to examine whether the regulatory 
distinctions underlying the certification and tracking and verification requirements are calibrated to the risk 
profiles of the ETP large purse seine fishery and a ll other fisheries. As noted in paragraph 6.67 above, we 
understand the Panels to have compared the risk profiles of the relevant fisheries for the purpose of this 
analysis, and we examine in section 6.1.5 below whether the Panels properly concluded that t he relevant 
regulatory distinctions are calibrated to these risk profiles.  
332 See para. 6.36 above. See also Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.155.  
333 We note that Mexico does not contest that the objectives of th e 2016 Tuna Measure include the 
protection of dolphins. (Mexico's appellant's submission, para.  71) 
334 See supra , fn 332. See also Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , 
para. 7.98. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.75.   We also note Mexico's argument that, because the Panels "disregarded"335 the fact that certain 
fisheries may have risk profiles equivalent to, or higher than, the risk profile of setting on dolphins  
in the ETP , the Pan els also failed to recognize that permitting access to the dolphin -safe label to 
tuna caught in such ocean areas undermines the measure's objectives.336 However, from our review 
of the Panels' find ings, it is clear that the 2016  Tuna Measure does not draw a regulatory distinction 
between the ETP setting -on-dolphins -fishery and other fisheries. As explained above, the eligibility 
criteria  distinguish between setting on dolphins and other fishing methods, while the certification 
requirement s and tracking and ve rification requ irements  distinguish between the ETP large purse 
seine fishery (whether by setting on dolphins or by other methods of purse seine fishing) and all 
other fisheries.337 It is on the basis of these regulatory distinctions that the Panels were req uired to 
compare the risk profiles of different fishing methods ( with respect to  the eligibility criteria) and 
fisheries ( with respect to  the certification and tracking and verification requirements), having 
established such risk profiles on the basis of t heir review of all relevant evidence of the risks to 
dolphins from different fishing methods as used in different ocean areas.  
6.76.   In any event, to the extent that Mexico is asserting that the Panels' analysis of risk profiles 
should have addressed all ocean areas because risks differ across different ocean areas, we have 
already addressed this argument above.338 As discussed, we agree that information pertaining to 
the risks to dolphins in individual fisheries is relevant, and should be taken into account, in a ssessing 
and comparing the overall relative risks of different fishing methods.339 On the basis of the evidence 
concerning the use of different fishing methods in different ocean areas, the Panels would then be 
able to compare the relative risks of specific fishing methods in order to examine whether the 
eligibility criteria are calibrated to such risks. To the extent that Mexico is asserting that the Panels 
failed to assess relevant evidence regarding the use of fishing methods in specific ocean areas, we 
address this argument in the context of our discussion of the Panels' assessment of risk profiles 
below.340  
6.77.   In sum, given that the eligibility criteria under the 2016 Tuna Measure distinguish  between 
setting on dolphins and other fishing methods, and Mexico h as not demonstrated how such a 
distinction would undermine the objective  of protecting dolphins, we consider that assessing whether 
this distinction is calibrated to different risks to dolphins required the Panels to compare, inter alia , 
the risk profiles of the relevant fishing methods. Based on the foregoing, we consider that Mexico 
has not demonstrated that the Panels erred by comparing the risk profiles of different fishing 
methods in applying the calibration analysis to the eligibil ity criteria. Specifically, we consider that 
the Panels were correct to compare, in the context of the eligibility criteria, the risk profiles of 
different fishing methods, given that the relevant regulatory distinction under the eligibility criteria 
is indeed on the basis of fishing methods. We also consider that the Panels acted appropriately by 
comparing the risk profiles of individual fisheries in the context of applying the calibration analysis 
to the certification and tracking and verification require ments, since those requirements make a 
distinction on the basis of fisheries (i.e. both fishing method and ocean area ).  
6.78.   In setting out the foregoing analysis, we are mindful of the need to avoid assessing each 
element of the measure at issue in isolation.  We recall that, in the first compliance proceedings, the 
Appellate  Body recognized that it may be appropriate for a panel "to proceed by assessing different 
elements of [a] measure in a sequential manner", provided that doing so does not "lead to the 
isolated consideration of a particular element" where the elements of a measure are closely 
interrelated.341 Thus, a segmented approach may raise concerns "when a panel fails to make an 
overall assessment that synthesizes its reasoning or intermediate conclusion s concerning related 
elements of a measure at issue so as to reach a proper finding of consistency or inconsistency in 
respect of that measure" .342 In our view, the Panels' approach as described above343, whereby they 
compared the risks of fishing methods  in the context of the eligibility criteria, and risks of fishing 
methods as used in specific ocean areas in the context of the certification and tracking and 
verification requirements, appears to comport with the Appellate  Body's guidance in the original and 
                                                
335 Mexico's appellant's submission, para. 167 . 
336 Mexico's appellant's submission, paras.  159-162 and 164 -171. 
337 See para.  6.65 above.  
338 See para.  6.63 above.  
339 See para.  6.63 above.  
340 See section 6.1.4 below.  
341 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.14-7.15. 
342 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.15. 
343 See para.  6.67 above.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  first compliance proceedings.344 Such an approach adapted the calibration analyses to reflect the 
specific distinctions made under the measure and allowed the Panels to evaluate the way in which 
the different interconnected aspects of the measure work togethe r. We also recall that, having 
examined sequentially, the eligibility criteria, the certification requirements, the tracking and 
verification requirements, and the determination provisions, the Panels provided an overall 
assessment of the consistency of th e 2016 Tuna Measure with Article  2.1.345 
6.1.3.3   Conclusion  
6.79.   Under Article  2.1 of the TBT Agreement , in order to determine whether the detrimental impact 
stems exclusively from a legitimate regulatory distinction, a panel must carefully scrutinize whether 
the technic al regulation at issue is even -handed in light of the particular circumstances of the case. 
In the present dispute, an examination of whether the 2016 Tuna Measure is consistent with 
Article  2.1 of the TBT Agreement  entails an assessment of whether the reg ulatory distinctions of the 
measure are calibrated to the risks to dolphins arising from different fishing methods in different 
areas of the ocean. Such assessment involves:  (i) an assessment of the overall relative risks of harm 
to dolphins arising from the use of different fishing methods in dif ferent ocean areas; and 
(ii) an assessment as to whether the differences in the dolphin -safe labelling conditions under the 
measure are appropriately tailored to, or commensurate  with, those respective risks. If co nducted  
properly , this calibration analysis would  encompass consideration of the rational relationship 
between the regulatory distinctions drawn by the 2016 Tuna Measure and its objectives.  Thus, there 
is no need to separately assess the rational relationship between the regulatory distinctions drawn 
by the measure and its objectives.  Furthermore, while risks of inaccurate labelling are relevant to 
the calibration analysis, this does not mea n that the applicable legal standard requires the Panels to 
determine whether the 2016 Tuna Measure is calibrated, inter alia , to the risk of inaccurate 
dolphin -safe information being passed to consumers.  
6.80.   In conducting the calibration analysis, it is neces sary to examine the risks to dolphins across 
all relevant ocean areas in which different fishing methods are practi sed. This does not mean that, 
under Article  2.1 of the TBT Agreement , a measure that seeks to protect dolphins must make all 
relevant regulat ory distinctions on the basis of both fishing method and ocean area. Rather, the 
nature of the calibration analysis to be conducted is informed by the nature of the regulatory 
distinctions made under the measure itself, and it is the regulatory distinction s causing the 
detrimental impact on imported products that must be calibrated to different risks to dolphins. The 
relevant regulatory distinctions that need to be examined for the purpose of calibration in this dispute 
include the distinction between setti ng on dolphins and other fishing methods (in the context of the 
eligibility criteria) and the distinction between the ETP large purse seine fishery and all other fisheries 
(in the context of the certification and the tracking and verification requirements) .  
6.81.   For these reasons, we do not consider that Mexico has established that the Panels, in 
considering that they were required to examine whether the 2016 Tuna Measure was calibrated to 
the risks to dolphins arising from the use of different fishing methods in different areas of the ocean, 
failed to include an inquiry into the nexus between the relevant regulatory distinctions and the 
objectives of the measure. We also disagree with Mexico that the Panels erred by comparing the risk 
profiles of different fish ing methods in applying the calibration analysis to the eligibility criteria. In 
our view, in the specific context of the 2016 Tuna Measure, in order to assess whether the 
detrimental impact on Mexican tuna products stems exclusively from a legitimate regu latory 
distinction, the Panels were required to assess whether the regulatory distinctions causing that 
detrimental impact are calibrated to different risks to dolphins, in terms of the overall relative risks 
to dolphins, taking into account the objectives  of the measure.  
6.1.4   The Panels' assessment of risk profiles  
6.82.   Mexico makes three sets of arguments with respect to  the Panels' assessment of different risk 
profiles, alleging that the Panels erred by: (i) failing to adequately evaluate the risk profiles of 
different fisheries; (ii) using the risk profile of setting on dolphins in the ETP as the benchmark for 
assessing the risk profiles of other fisheries; and (iii) relying predominantly on "per set" evidence 
for measuring the level of risks to dolphins, and igno ring other relevant evidence in their evaluation 
                                                
344 We address whether the Panels' analysis took into account the manner in which the discrete 
elements of the 2016 Tuna Measure are cumulative and highly interrelated in section 6.1.5 below.  
345 See Panel Reports, section 7.8.6. See also section 6.1.5.5 below.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  of the risk profiles.346 The United  States  submits that the Panels correctly assessed the risk profiles 
of different fishing methods, as used in different areas of the ocean.347 The United  States  argues 
that cer tain aspects of Mexico's arguments appear to pertain to the Panels' appreciation of the facts 
and therefore fall outside the scope of this appeal, since Mexico did not raise any claims of error 
under Article  11 of the DSU.348 Furthermore, in the United  State s' view, the Panels acted correctly 
in relying primarily on per set evidence, and not relying on evidence that would have been misleading 
and inapposite for comparing the relative risk profiles of different fishing methods and fisheries.349 
We begin by recal ling the Panels' assessment of different risk profiles, before turning to address 
each of the three sets of arguments put forward by Mexico.350  
6.1.4.1   The Panels' findings  
6.83.   The Panels recalled that the Appellate  Body criticized the first compliance panel for failin g to 
analyse "the overall levels of risks in different fisheries, and how these fisheries compared to each 
other" despite "considerable evidence" before it in this regard, in particular because it had failed to 
consider the relative risks arising from obse rved mortalities and serious injuries to dolphins.351 The 
Panels therefore considered that it was necessary "to establish the risk profiles of the relevant fishing 
methods in different areas of the ocean, taking into account data on both observable and 
unobs ervable harms".352 
6.84.   In establishing the risk profiles of different fishing methods in different areas of the ocean, 
the Panels considered it appropriate to "rely to the greatest extent possible on a quantitative 
analysis, and recur to a qualitative assessment  in cases where this seem[ed] to be the most 
reasonable avenue to properly gauge and describe the risks at issue ."353 The Panels also highlighted 
the importance of a "standardized benchmark or metric when determining and comparing the 
different risk profiles ", emphasizing that "[b]ecause the different scientific evidence on the record 
does not necessarily follow the same methodology or present its results in a homogeneous and 
consistent manner, there is a need to use a standardized benchmark so that compariso ns across 
studies are meaningful and adequate."354 The Panels considered several differen t possible 
standardized metrics and ultimately adopted a "per set " methodology that entailed averaging the 
total number of a particular indicator of adverse effects to d olphins by the number of operations of 
                                                
346 Mexico's appellant's submission, paras.  154-225. As further discussed below, per set evidence 
involves averaging the total number of a particular indicator of adverse effects to dolphins, such as mortalities 
and serious injuries, by the number of operations of a particular type of fishing gear used in a particular fishery 
in a given time period. (See para. 6.84 below)  
347 United  States' appellee's submission, paras.  96-203. 
348 See e.g. United  States' appellee's submission, paras.  114, 138, 152, 172 -173, and 192.  
349 United  States' appellee's submission, paras.  151-203. 
350 We note that, in its appellant's submission, Mexico states that, although "the evaluation of the  
risk profiles in certain respects required scientific expertise …, the Panels declined t o consult with 
experts  … [and i]n Mexico's view, the Panels did not make an appropriate exercise of their discretion under 
Article  13 of the DSU in declining to request technical advice from experts". (Mexico's appellant's submission, 
paras.  155 and 157) T he United  States, in its appellee's submission, stated that "Mexico makes no appeal with 
respect to the Panels' decision not to consult experts, and thus there is no reason, or basis, for the 
Appellate  Body to engage on this aspect of the Panel Reports." ( United  States' appellee's submission, para.  98 
(fn omitted)) However, Mexico clarified at the hearing that it was not asserting any legal error by the Panels in 
this respect, and that its comments regarding Article  13 of the DSU were not relevant to the sp ecific issues 
before the Appellate  Body. We therefore do not address this aspect of Mexico's appellant's submission.  
351 Panel Reports, para.  7.146 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.243).  
352 Panel Rep orts, para.  7.149.  
353 Panel Reports, para.  7.170.  
354 Panel Reports, para.  7.171.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  a particular fishing gear used in a particular fishery in a given time period.355 The Panels found that 
relevant indicators included observed mortalities, serious injuries, and tuna -dolphin interactions.356 
6.85.   The Panels als o made several distinctions between different types  of harm occurring to 
dolphins.357 The Panels first distinguished between observable harm (i.e. any type of harm that can 
be detected and reported) and unobservable harm (i.e. the type of harm that occurs bu t cannot be 
detected during the set itself). As regards observable harm, the Panels also distinguished between 
observed  harm (i.e. the harm that is observable and that has, as a matter of fact, been detected 
and reported during the conduct of a set) and unobserved  harm (i.e. the type of harm that is 
observable but that has not been detected or reported during the conduct of a set). Given that, by 
definition, there can be no observer -based evidence of such unobserved but observable harm, the 
Panels looked at  the level of association between dolphins and tuna as a proxy in order to determine 
probable levels of unobserved but observable harm.358 Finally, the Panels distinguished between 
direct harm (caused by direct interaction with fishing gear) and indirect harm (consequent upon 
other harm sustained as a result of direct interaction with fishing gear).  
6.86.   The Panels proceeded to conduct their analysis of risk profiles by distinguishing between seven 
different fishing methods, namely: purse seine fishing by setting  on dolphins; purse seine fishing 
without setting on dolphins; gillnet fishing; longline fishing; trawl fishing; tuna handlining; and pole 
and line fishing. The Panels  found  that purse  seine fishing  by setting  on dolphins359 causes  serious  
injuries  to dolphins.360 In particular,  the Panels  found  that, in the ETP, while the evidence  suggested  
that setting  on dolphins  does not pose a very high risk of observable  serious  injury361, such serious  
injury  is less frequent  than mortality362, and the likelihood  of unobserved  mortality  or serious  injury  
is present  in every  set, as a consequence  of the tuna-dolphin  association  in that ocean  area.363 The 
Panels also found that setting on dolphins causes unobservable harms as a result of the chase  and 
encirclement process itself364, including "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".365 
                                                
355 Panel Reports, para.  7.214. The Panels considered Mexico's proposed methodologies, consisting of: 
(a) a Potential Biological Removal (PBR) methodology, measuring the maximum n umber of animals that may 
be removed from an animal stock without affecting that stock's optimum sustainable population; and (b) either 
as an alternative to a PBR methodology, or to be read in conjunction with PBR evidence, a comparison of the 
absolute lev els of dolphin mortalities and serious injury from different fishing methods and fishing areas. The 
Panels rejected the PBR methodology and relied on evidence of absolute levels of adverse effects to dolphins in 
situations where the Panels considered the p er set evidence to be insufficient. (Ibid., paras.  7.175 -7.195. See 
also Mexico's first written submission to the Panels, para.  247) As discussed in section 6.1.4.4 below, Mexico 
appeals the Panels' rejection of such benchmarks.  
356 Panel Reports, para.  7.204. 
357 Panel Reports, paras.  7.245 -7.251.  
358 Panel Reports, para.  7.253. The Panels explained that "the magnitude of interactions does not 
indicate the number of dolphins that actually do suffer unobserved harms, but rather, the upper bound of 
dolphins that c ould suffer such harms. The lower the interaction the less likely it is for the relevant fishing 
method to cause harms to dolphins." (Ibid.)  
359 Purse seine fishing by setting on dolphins consists of "chasing and encircling the dolphins with a 
purse -seine ne t in order to catch the tuna swimming beneath the dolphins" in areas where there is an 
association between tuna and dolphins. (Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , 
para. 6.5) According to the Panel Reports, "[s]peedboats are used to chase down the dolphins and herd them 
into a tight group; then the net is set around them. The tuna -dolphin bond is so strong that the tuna stay with 
the dolphins during this process, and tuna and dolphins are captured together in the net. … If all goes well, the 
dolphins are released alive, but … things can go wrong, and when they do, dolphins may be killed." (Panel 
Reports, para.  7.258 (quoting T.  Gerrodette, "The Tuna -Dolphin Issue", in Perri n, Wursig, and Thewissen 
(eds.), Encyclopedia of Marine Mammals , 2nd edn (Elsevier, 2009) (Panel Exhibit USA -12), p.  1192))  
360 Panel Reports, para.  7.281.  
361 Panel Reports, para.  7.282.  
362 The Panels found that the mortality rate per 1,000 sets associated wit h setting on dolphins in the ETP 
ranged between 69.42 in 2015 and 113.38 in 2009, with an average of 91.15 mortalities. (Panel Reports, 
para. 7.280)  
363 Panel Reports, para.  7.285.  
364 Panel Reports, para.  7.308.  
365 Panel Reports, para.  7.309 (quoting Appellate  Body Report, US – Tuna II (Mexico) , fn 663 to 
para. 330, in turn referring to Original Panel Report, paras.  7.491 -7.506).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.87.   Regarding  purse  seine fishing  without  setting  on dolphins366, the Panels looked at evidence of 
mortalities and serious injuries to dolphins in the ETP, Western and Central  Pacific Ocean (WCPO), 
Indian Ocean , and Eastern Tropic Atlantic Ocean (ETAO) .367 The Panels concluded that while purse 
seine fishing without setting on dolphins has killed and seriously injured dolphins in the past and has 
the potential of doing so in the future, the risk profile of this fishing method is generally low as it 
does not require inte raction with dolphins in order to spot tuna.368 The Panels considered that this 
fishing method has a "relatively low risk profile in terms of both observed and unobserved mortality 
and serious injury" .369 The Panels further concluded that the extent of unobser ved harm  in the ETP 
may be low, but that without direct evidence on the record they were unable to base their finding 
on a precise quantification.370 The Panels also found that the likelihood of unobserved harm to 
dolphins in the WCPO , the Indian Ocean,  and the ETAO is low because  interactions with dolphins are 
infrequent.371 Additionally, the Panels found that purse seine fishing without setting on dolphins in 
the ETP, the WCPO, the Indian Ocean, and the ETAO does not cause the kinds of unobservable harms 
caused by purse seine fishing by setting on dolphins in the ETP, since purse seine fishing without 
setting on dolphins does not require interaction with dolphins.372 
6.88.   With respect to  gillnet fishing373, the Panels found that this fishing method poses high levels 
of observable harm to dolphins in certain areas of the ocean, but does not pose the same level of 
harm in other areas.374 The Panels further noted that the evidence presented in relation to 
"ghost  fishing"375 indicated that ghost fishing does give rise to unobse rved harms, but that such 
harms were at least observable , and not like the kinds of unobservable harm that are caused by 
setting on dolphins.376  
6.89.   As regards longline377 and handline378 fishing, the Panels found that the risk profiles of these 
methods were low in terms of observable harms, and that they do not cause the kinds of 
unobservable harm caused by setting on dolphins.379 With regard to trawl fishing380, the Panels found 
that this me thod is a low -to-moderate -risk fishing method in terms of observed mortalities and 
observable harm, as it entails very little, if any, interaction with dolphins.381 The Panels also found 
that trawl  fishing does not cause the kinds of unobservable harm caused  by setting on dolphins.382 
Regarding the pole and line  fishing method, the Panels found no reports of any dolphins being killed 
                                                
366 In addition to setting on dolphins, purse seine fishing is also conducted by setting on: (i)  seamounts 
(a category of oceanic ridge s); (ii) floating objects; or (iii) schools of tuna (i.e.  where the set is not based on 
the tuna's association with any other marine feature/object/animal). (Panel Reports, paras.  7.313 -7.316 
(referring to Food and Agricultural Organization of the United  Nations (FAO), FAO Fisheries and Aquaculture 
Technical Paper 568, Bycatch and Non -Tuna Catch in the Tropical Purse Seine Fisheries of the World  (Rome, 
2013) (Panel Exhibit USA -60), pp.  17-24)) 
367 Panel Reports, paras.  7.326 -7.399.  
368 Panel Reports, para.  7.400. 
369 Panel Reports, para.  7.401.  
370 Panel Reports, para.  7.334.  
371 Panel Reports, paras.  7.334, 7.367, 7.385, and 7.398.  
372 Panel Reports, para.  7.401.  
373 Gillnets are nets "set on the seafloor … or floated vertically" using buoys (i.e. driftnets or drift 
gillnets). (Panel Reports, paras.  7.404 -7.405 (referring to Natural Resources Defense Council, Net Loss: The 
Killing of Marine Mammals in Foreign Fisheries  (New York, January 2014) (Panel Exhibit MEX -18), p. 13; FAO, 
"Tuna Drifting Gillnet" (Panel Exhibit MEX -15))) 
374 Panel Reports, para.  7.444.  
375 Ghost fishing occurs when fishing gear (such as gillnets) continue to cause harm to marine life (such 
as dolphins) after being lost or discarded. (Panel Reports, paras.  7.410 and  7.447 (referring to NOAA, 2015 
NOAA Marine Debris Program Report, Impact of "Ghost Fishing" via Derelict Fishing Gear  (Charleston, March 
2015) (Panel Exhibit MEX -104), p. 6))  
376 Panel Reports, paras.  7.450 -7.457.  
377 Tuna longlining is "'a passive type of fishing technique makin g use of lines with baited hooks as 
fishing gear'", with a typical set consisting of "'200 or more units or "baskets" connected together, with a buoy 
at each connection, and a total of about 3,000 hooks'". (Panel Reports, para.  7.458 (quoting FAO, "Industr ial 
Tuna Longlining" (Panel Exhibit MEX -26), pp. 2 -3)) 
378 A tuna handline is a "'single vertical line with one barbed hook at the distal point'", or several barbed 
hooks connected to branchlines along the mainline at regular intervals. (Panel Reports, para.  7.495 (quoting 
FAO, "Tuna Handlining" (Panel Exhibit MEX -38))) 
379 Panel Reports, paras.  7.481 and 7.511.  
380 Trawl fishing consists of "'towing a net … either with bottom contact or in midwater'", catching fish 
and shellfish by filtering the water. (Panel Re ports, para.  7.482 (quoting FAO, "Trawl Nets" (Panel Exhibit 
MEX-37))) 
381 Panel Reports, paras.  7.493 -7.494.  
382 Panel Reports, para.  7.494.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  or seriously injured as a result of pole and line fishing, and no evidence that any unobservable harm 
is caused to dolphins.383 The Panels concluded that the risk profile is very low.384  
6.90.   Having set forth their analysis of the seven fishing methods, the Panels conducted an overall 
relative assessment, in which they "provide[d] a comparative assessment of method -specific 
findings".385 The Panels concluded that, given the differences between setting on dolphins and each 
of the other six methods with respect to observable harm to dolphins, and taking into account that 
none of the other methods causes the kinds of unobservable harms caused by setting on dolphins, 
"overall, the risk profile of setting on dolphins is much higher tha n that of each of the other six  fishing 
methods used to catch tuna."386 
6.1.4.2   Whether the Panels erred by failing to assess the risk profiles of individual 
fisheries  
6.91.   We first turn to Mexico's argument that the Panels did not properly determine the risk profiles 
of different fishing methods as used in different areas of the oceans, but erroneously limited their 
assessment of risk profiles to the seven tuna -fishing methods, witho ut assessing the risk profiles for 
individual ocean areas.387 Mexico acknowledges that the Panels did address evidence with respect 
to ocean areas for certain of the  fishing methods they assessed388, but argues that the Panels erred 
by forming conclusions on t he fishing methods as a whole, and thereby "effectively averaged or 
sampled the overall relative risks or levels of harm over all of the fisherie s that use the method ".389 
In particular, Mexico submits that the Panels effectively "disregarded that there are very high risks 
to dolphins" from gillnet fishing, longline fishing, and trawl  fishing, in certain ocean areas.390 Mexico 
also argues that the Panels erred by failing to address the risk profile of purse seine fishing by setting 
on dolphins in ocean areas ot her than  the ETP.391  
6.92.   The United  States  submits that the Panels did assess the risks to dolphins in individual 
fisheries.392 The United  States  indicates that, with respect to  observable harms, the Panels assessed 
"each fishery for which there was probative evi dence on the record" , and , on th is basis, "drew 
conclusions about the risk of observable harms posed by the different fishing methods" .393 With 
respect to  unobservable harms, the United  States  asserts that the Panels concluded that "none of 
the other fishing methods is capable of causing the sort of unobservable harms caused by dolphin 
sets", and that this conclusion is applicable "to each and all of the fisheries where these fishing 
methods ar e employed".394 The United  States  indicates that it was on the basis of these findings 
that the Panels "drew conclusions about the risk profile of each tuna fishing method 'as used in 
                                                
383 Panel Reports, para.  7.515.  
384 Panel Reports, para.  7.516.  
385 Panel Reports, para.  7.517. The Panels explained that t he reason for conducting this comparative 
assessment was that "the issue before [them was] whether the 2016 Tuna Measure, under which tuna 
products obtained from tuna caught by setting on dolphins are ineligible for the dolphin -safe label whereas 
tuna prod ucts obtained from tuna caught by the other six methods cited above are conditionally eligible for 
that label, is calibrated to different levels of risks posed to dolphins by different fishing methods in different 
areas of the ocean." (Ibid.)  
386 Panel Repor ts, para.  7.525.  
387 Mexico's appellant's submission, para.  161. 
388 Specifically, purse seine fishing without setting on dolphins, gillnet fishing, longlining, trawl fishing, 
and handlining. (See Mexico's appellant's submission, para.  162) 
389 Mexico's appellan t's submission, para.  164 (referring to Panel Reports, para.  7.517).  
390 Mexico's appellant's submission, para.  167. See also Mexico's appellant's submission, paras.  168-170 
(referring to Panel Reports, paras.  7.438, 7.440 -7.443, 7.466 -7.467, 7.473 -7.474, 7. 489-7.490, 
and 7.493 -7.494).  
391 Mexico's appellant's submission, para.  162. We note that Mexico's appellant's submission additionally 
states that "[t]he Panels did not address ocean areas in the context of the risk profile for pole -and-line fishing." 
(Ibid. ) However, Mexico also indicated in its appellant's submission that "the parties agreed during the first 
compliance proceeding that this method is not known to harm dolphins." (Ibid., fn  21 to para.  22) Mexico 
clarified at the hearing that pole and line fi shing was included in paragraph 162 to be complete in describing 
what the Panels said, and that Mexico does not take issue with the Panels' findings on pole and line fishing.  
392 United  States' appellee's submission, paras.  125-126. 
393 United  States' appellee 's submission, para.  125 (referring to Panel Reports, paras.  7.401 (purse 
seine fishing other than by setting on dolphins), 7.475 (longline fishing), 7.494 (trawl fishing), 7.511 
(handlining), 7.514 -7.515, and 7.520 (gillnet fishing)).  
394 United  States' appellee's submission, para.  125 (referring to Panel Reports, paras.  7.332 -7.334, 
7.365 -7.367, 7.383 -7.385, 7.396 -7.398, 7.440 -7.444, 7.466 -7.471, 7.475, 7.488 -7.494, 7.511, 7.514 -7.515, 
and 7.521).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  different areas of the ocean'".395 The United  States  further argues that Mex ico's assertion that certain 
fisheries are "high risk" is based on Mexico's own definitions of "high risk", as well as certain 
misstatements of the Panels' analysis of the evidence, and reflects arguments that the Panels 
rejected.396 
6.93.   We recall that , in order  to properly assess whether the relevant regulatory distinctions under 
the 2016 Tuna Measure are properly calibrated to the risks to dolphins, the Panels were, inter alia , 
required to compare the risk profile of "setting on dolphins" with the risk profiles  of other individual 
fishing methods. In order to make such a comparison, the Panels were necessarily required  to 
establish the risk profiles of different fishing methods. We therefore consider it appropriate for the 
Panels to have formed a conclusion for each individual fishing method, for the purposes of conducting 
the calibration analysis.  
6.94.   We note, however, that , in forming a conclusion on each fishing method, the Panels were 
required to take into account all evidence provided to the m with respect to  each ocean area in which 
each fishing method is used. Furthermore, it is uncontested that, in the context of assessing whether 
the certification and tracking and verification requirements are calibrated to the risks to dolphins, 
the Panels were required to c ompare the risk profiles of the ETP large purse seine fishery and other 
individual fisheries.397 It was therefore incumbent on the Panels to not only draw conclusions on 
each fishing method as a whole, but also examine the risks to dolphins in each individua l fishery.  
6.95.   In this respect, Mexico has not raised any claims under Article  11 of the DSU alleging that the 
Panels failed to assess any individual fishery for which evidence was placed before them. We also 
note that the Panels explicitly referred to eviden ce regarding individual fisheries for the purpose of 
examining the relevant fishing methods.398 Furthermore, certain of the evidence provided to the 
Panels was of a general nature, such that it pertained to every  fishery in which that fishing method 
was prac tised.399 We therefore consider that Mexico has not demonstrated that the Panels failed to 
examine each individual fishery for which evidence was provided.  
6.96.   Mexico additionally argues that, in drawing an overall conclusion on the risk profile for each 
fishing method examined, the Panels effectively averaged or sampled the overall relative risks or 
levels of harm over all of the fisheries that use that method, and, in doing so, disregarded that there 
are very high risks to dolphins in certain ocean areas .400 For example, Mexico contrasts the Panels' 
finding that "gillnet fisheries, and driftnet fisheries in particular, have caused, in some circumstances 
and in certain regions, levels of observable harms greater than those caused by setting on dolphins 
in the ETP" with the Panels' conclusion that "while gillnet fishing may be harmful to dolphins, it does 
not necessarily  cause such harms in every area of the ocean".401  
6.97.   We do not see a contradiction between a finding that a particular fishing method poses high 
risks in  some  fisheries , but not others, and a conclusion that the fishing method as a whole has a 
lower risk profile than the method of setting on dolphins. We recall that, according to the Panels, 
setting on dolphins poses a high risk to dolphins in all fisherie s for which evidence was provided to 
the Panels402, whereas , for gillnet fishing, the Panels found that "gillnet fishing causes considerable 
                                                
395 United  States' appellee's submission, para.  125 (quotin g Panel Reports, para. 7.517; referring to 
Panel Reports, paras.  7.402, 7.457, 7.480, 7.493 -7.494, 7.511, 7.516 -7.518, 7.520 -7.523, and  7.525).  
396 United  States' appellee's submission, para.  126 (referring to Mexico's appellant's submission, 
paras.  168-170). The United  States elaborates that Mexico specifically refers to the Panels' findings on Indian 
Ocean gillnet fisheries, absolute levels of mortalities caused by longline fishing in the Pacific Ocean, PBR 
evidence concerning an additional longline fishery , and per set evidence of mortalities in a North Atlantic trawl 
fishery. The United  States recalls that the Panels "rejected" the exhibits that Mexico relied on in defining the 
Pacific Ocean longline fishery and North Atlantic trawl fisheries as "high risk ", and explained why they chose 
not to rely on PBR evidence. Furthermore, with respect to the Indian Ocean gillnet fisheries, the Panels 
explained that the 2016 Tuna Measure "appropriately addresses the risks to dolphins in that fishery". (See 
ibid., fn  285 to para.  126) 
397 Mexico's and the United  States' responses to questioning at the hearing.  
398 For example, with respect to purse seine fishing without setting on dolphins, the Panels assessed the 
risks to dolphins in the ETP, the WCPO, the Indian Ocean, and  the ETAO. (Panel Reports, paras.  7.326 -7.399)  
399 For example, with respect to pole and line fishing, the Panels examined evidence pertaining to the 
fishing method in general, without specifying any particular fisheries. (Panel Reports, paras.  7.514 -7.516)  
400 Mexico's appellant's submission, paras.  164 and 167.  
401 Mexico's appellant's submission, para.  168 (quoting Panel Reports, paras.  7.441 -7.442 (emphasis 
original)).  
402 Panel Reports, paras.  7.256 -7.311.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  observable harms to dolphins in different areas of the ocean"403 but also that "there are other areas 
where this partic ular method does not cause such harms ."404 Furthermore, we do not consider that , 
merely by forming conclusions on each fishing method as a whole , the Panels necessarily conflated 
the risk profiles of individual fishing methods with the risk profiles of indiv idual fisheries . In light of 
the different sets of distinctions drawn under the measure, the Panels were required to compare the 
risk profiles of fishing methods in the context of assessing the eligibility criteria, and to compare the 
risk profiles of indi vidual fisheries when assessing the certification and tracking and verification 
requirements. The Panels were therefore obliged to form conclusions on the risk profiles of different 
fishing methods, in the process of which the Panels were also required to look at the evidence of 
risks to dolphins in individual ocean areas. In our view, the fact that the Panels made conclusions 
on fishing methods in assessing the eligibility criteria does not indicate that they inappropriately 
applied the calibration analysi s to the certification and tracking and verification requirements.  
6.98.   In any event, to the extent that Mexico considers that the Panels' conclusions on each 
individual fishing method were flawed, because the Panels incorrectly weighed and balanced the risk 
profiles of each individual fishery  in drawing generalized conclusions on each fishing method  as a 
whole, we consider that such a question relates to the Panels' appreciation of the evidence and the 
facts, rather than the Panels' application of the legal st andard under Article  2.1 of the 
TBT Agreement . However, Mexico has not challenged the Panels' appreciation of the evidence under 
Article  11 of the DSU. Consequently, we do not consider it necessary or appropriate to review 
whether the Panels' conclusions o n each fishing method were justified on the basis of the evidence 
placed before them.405  
6.99.   It therefore suffices for our purposes to note that the Panels assessed each individual fishery 
for which evidence was given to them, and, on the basis of th ese assessm ents, drew conclusions on 
the risk profile of different fishing methods.406 We therefore do not consider that Mexico has 
demonstrated that the Panels failed to assess the risk profiles of individual fisheries or that the 
Panels erred in drawing conclusions o n the risk profile of each fishing method on the basis of their 
examination of the evidence before them (including evidence pertaining to each individual fishery).  
6.1.4.3   Whether the Panels erred by using the risk profile of setting on dolphins in the 
ETP as a b enchmark  
6.100.   We turn now to Mexico's argument that the Panels erred by using the risk profile of setting 
on dolphins in the ETP as a benchmark – referred to by Mexico as the "ETP  benchmark"407 – for 
assessing the risk profiles of other fisheries. Mexico asserts that a "benchmark cannot be used to 
objectively assess the circumstances that constitute the benchmark itself".408 Rather, Mexico asserts 
that the Panels should have relied on an "independent and objective standard or point of reference 
against which the overall relative risks or levels of harm arising from each" fishery could be 
assessed.409 Mexico also argues that the  Panels erred by distinguishing setting on dolphins in the 
ETP from other fisheries, because the "mere fact that the risk profiles of other [fisheries] … may be 
different from or comparatively lower than the risk profile of [setting on dolphins] in the ETP  does 
not mean that the regulatory distinctions are 'calibrated' to the different overall relative risks or 
levels of harm arising from different [fisheries]".410 Mexico further submits that the Panels' reliance 
on the "ETP benchmark" for comparing the risk profiles of other fisheries resulted in the Panels 
focusing their analysis on "qualitative attributes that are unique" to the ETP setting -on-dolphins 
fishery.411 Mexico refers to the Panels' findings on unobservable harms with respect to  "alleged stress 
effects on dolphins in the ETP"412, and considers that the Panels' emphasis on this kind of 
                                                
403 Panel Reports, para.  7.440.  
404 Panel Reports, para.  7.442.  
405 Appellate  Body Report, US – Large Civil Aircraft (2nd complaint) , paras.  955-958. See also 
Appellate  Body Report, Mexico – Anti-Dumping Measures on Rice , para. 274.  
406 We note that the only evidence adduced to the Panels with respect to any individual fishery where 
setting on dolphins is practised was evidence related to the ETP. (See Panel Reports, paras.  7.270 -7.311)  
407 Mexico's appellant's submission, paras.  173 and 178.  
408 Mexico's appellant's submission, para.  176. 
409 Mexico 's appellant's submission, para.  179. 
410 Mexico's appellant's submission, para.  181. 
411 Mexico's appellant's submission, para.  186. 
412 Mexico's appellant's submission, para.  187 (referring to Panel Reports, para. 7.310).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  unobservable harm caused the Panels "to disregard the Appellate  Body's direction to take into 
account the overall effects of each fishing method".413 
6.101.   The United  States  argues that the Panels' approach was fully in line with the calibration 
analysis as set forth by the Appellate  Body in previous proceedings.414 The United  States  notes that 
Mexico itself has consistently argued that "the ETP large purse [seine] fishery is a prop er comparator 
to determine whether the regulatory distinctions are even -handed, both in the previous compliance 
proceeding and before the Panels."415 As for Mexico's arguments regarding different types of harm, 
the United  States  considers that the Panels did  take into account all evidence related to any kinds 
of unobservable harms, including those identified by Mexico.416 According to the United  States , "the 
Panels found that, while some evidence suggested that 'ghost fishing linked to gillnets poses some 
risks to dolphins, … its extent is unclear' … [and] 'the absolute numbers of marine mammals involved 
are relatively small' ."417 
6.102.   As discussed in paragraphs  6.72-6.73 above , in order to be consistent with Article  2.1 of the 
TBT Agreement , it is the regulatory disti nctions causing the de trimental impact under the 2016  Tuna 
Measure that must be calibrated to different risks to dolphins. Thus, a proper calibration analysis in 
this dispute does not mean that the Panels were requi red to examine whether the 2016  Tuna 
Measure makes all relevant regulatory distinctions on a fishery -by-fishery basis.418 We have also 
noted that, in light of the relevant distinctions made under the measure at issue, the Panels were 
correct to have compared the risk profile of purse seine fish ing by setting on dolphins with the risk 
profiles of other fishing methods for the purpose of examining the eligibility criteria, and to have 
compared the risk profile of the ETP large purse seine fishery with the risk profiles of all other 
fisheries for the purpose of examining the certification and tracking and verification requirements.419  
6.103.   We further note that the Panels di d not, as Mexico contends, use setting on dolphins in the 
ETP as a "benchmark". Indeed, the Panels did not use the expression "ETP ben chmark" in their 
analysis of risk profiles. Rather, the Panels referred to this expression solely in the context of 
describing the United  States ' explanation regarding the determin ation provisions under the 
2016 Tuna Measure.420 In contrast, in their analysi s of risk profiles, the Panels used the word 
"benchmark" to describe a "standardized benchmark or metric" when assessing and comparing 
different risk profiles.421 In this respect, the Panels were referring to the use of an appropriate metric, 
or methodology,  for comparing the risks to dolphins in different fisheries. As explained above, the 
Panels relied primarily on data reflecting the numbers of observed mortalities, serious injuries, and 
tuna-dolphin interaction s on a per set  basis, in different fisheries,  to compare the risks to dolphins 
from different fishing methods and in different fisheries.422 Where such data were unavailable, the 
                                                
413 Mexico's appellant's submission, par a. 189 (referring to Appellate  Body Report, US – Tuna II 
(Mexico) (Article  21.5 – Mexico) , paras.  7.152 and 7.155 -7.156).  
414 United  States' appellee's submission, paras.  139-143. 
415 United  States' appellee's submission, para.  142 (referring to Appellate  Body Report, US – Tuna II 
(Mexico) (Article  21.5 – Mexico) , para.  7.112; First Compliance Panel Report, paras.  7.111 -7.112; Mexico's 
first written submission to the Panels, para.  256; Mexico's second written submission to the Panels, paras. 248, 
256, and 263). (fns omitted)  
416 United  States' appellee's submission, para.  147. 
417 United  States' appellee's submission, para.  148 (quoting Panel Reports, para.  7.448).  
418 See paras. 6.64 -6.77 abo ve. 
419 See paras.  6.65-6.77 above.  
420 Panel Reports, paras.  7.417 and 7.685. The Panels noted the United  States' explanation that NOAA 
compared the bycatch rates (i.e. number of dolphins killed per ton of tuna landed) of the Indian Ocean gillnet 
fishery to t hose caused by setting on dolphins in the ETP (the "ETP benchmark" to which Mexico refers). NOAA 
concluded, on this basis, that there was a "regular and significant" dolphin mortality rate in the Indian Ocean 
gillnet fishery. Under the structure of the 201 6 Tuna Measure, this formal determination resulted in tuna from 
the Indian Ocean gillnet fishery being subject to stricter certification and tracking and verification requirements 
than would otherwise have been required to gain access to the dolphin -safe l abel. (See also ibid., 
paras.  7.67-7.69)  
421 Panel Reports, para.  7.171.  
422 See para. 6.84 above. Furthermore, Mexico clarified at the hearing that the Panels' reliance on 
per set evidence constitutes an independent and objective standard or point of referenc e on which the Panels 
should have relied. Mexico nonetheless argued that, in addition to relying on per set evidence, the Panels 
should have also taken into account evidence related to the sustainability of different dolphin populations, as 
well as absolut e levels of adverse effects in different areas. We address these aspects of Mexico's arguments in 
section 6.1.4.4 below.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Panels relied on other sources of information, including general information that relates to all 
fisheries in which a partic ular fishing method is practi sed.423  
6.104.   Once the Panels had assessed the risk profiles of different fishing methods and fisheries on 
the basis of per set data and other relevant evidence, the Panels did compare the risk profile of 
setting on dolphins with the risk profile s of other fishing methods in the context of both their 
assessment of risk profiles and their examination of whether the eligibility criteria are calibrated to 
different risks to dolphins.424 As we have discussed above, such a comparison of fishing methods 
was, inter alia , required in light of the applicable legal standard and the circumstances of this 
dispute.425 As to Mexico's contention that the Panels' assessment of the eligibility criteria was based 
on a comparison of the risk profile of setting on dolphins in the ETP with the risk profiles of other 
fishing methods426, we note that certain aspects of the Panels' assessment of the risk profile of  
setting on dolphins were indeed limited to the u se of this fishing method in the ETP.427 This, however, 
was due to the fact that the only fishery -specific evidence provided to the Panels concerning the use 
of setting on dolphins pertained to the use of this method in the ETP.428 Furthermore, other aspects 
of the Panels' examination of the risks associated with setting on dolphins were not limited to the 
ETP, but more broadly pertained to setting on dolphins anywhere in the world.429 
6.105.   We note Mexico's argument that, by "distinguishing Mexico's fishing method [i.e. setting on 
dolphins] in the ETP from all other fishing methods in all other areas of the ocean s … the Panels did 
not assess whether tuna caught by other fishing methods in other ocean areas should also be 
excluded from access to the label".430 In Mexico's  view, the "mere fact that the risk profiles of other 
fishing methods in other ocean areas may be different from or comparatively lower than the risk 
profile of [setting on dolphins] in the ETP does not mean that the regulatory distinctions are 
'calibrated ' to the different overall relative risks or levels of harm arising from different fishing 
methods in different ocean areas".431 Mexico refers to the Appel late Body's statement that 
even-handedness depends not only on the level of risk associated with the fi shing method suffering 
from a denial of access, but "also on whether the risks associated with other fishing methods in 
other fisheries are addressed, commensurately with their respective risk profiles, in the labelling 
conditions that apply in respect of tuna caught in such other fisheries".432 In Mexico's view, the 
Panels did not assess "whether the risks or levels of harm associated with other fishing methods in 
other fisheries are addressed, commensurately with their respective risk profiles, in the label ling 
conditions that apply in respect of tuna caught in such other fisheries" .433 
6.106.   In the United  States ' view, Mexico's approach "directly conflicts not only with the design, 
architecture, and revealing structure of the [Tuna Measure], but also with the Appel late Body's 
analysis in the first compliance proceeding" .434 The United  States  argues that the relevant question 
under Article  2.1 is whether the differences arising under the relevant regulatory distinctions are 
commensurate with different risks to dolphins . According to the United  States , perfection is not an 
                                                
423 See e.g. Panel Reports, paras.  7.212, 7.434, 7.446 -7.456, 7.476 -7.481, and 7.514.  
424 See paras. 6.67 and 6.90 below.  
425 See para. 6.77 above.  
426 Mexico's appellant's submission, paras.  175 and 186.  
427 Specifically, the Panels' assessment of observed mortality and serious injury, observable serious 
injury, and unobserved mortality and serious injury appears to be based on evidence that is sp ecific to the ETP. 
(See Panel Reports, paras.  7.279 -7.285) By contrast, we note that the Panels' conclusion that "setting on 
dolphins causes unobservable harms" is not specific to the ETP and, consequently, applies to the fishing 
method as a whole. (See ib id., para.  7.309)  
428 See supra , fn 406.  
429 For instance, with respect to unobservable harms, the Panels referred to the first compliance panel's 
findings that certain unobservable harms "occur as a result of the 'chase itself'". (Panel Reports, para.  7.286 
(referring to Original Panel Report, para.  7.504)) Further, on examining the evidence submitted by the parties, 
the Panels concluded that "because chasing and encirclement are essential elements of the process of setting 
on dolphins, setting on dolphins can not be used without putting dolphins at risk, even though that risk may not 
eventuate in every set." (Ibid., para.  7.310)  
430 Mexico's appellant's submission, para.  182. 
431 Mexico's appellant's submission, para.  181. 
432 Mexico's appellant's submission, para.  182 (quoting Appellate  Body Report, US – Tuna II (Mexico) 
(Article  21.5 – Mexico) , para.  7.126). Mexico argues that "[p]ermitting access to the label to tuna caught by 
such methods in [high -risk] ocean areas contradicts and undermines the objective of the t una measure to 
discourage fishing practices that adversely affect dolphins." (Ibid., para.  167) 
433 Mexico's appellant's submission, para.  183. 
434 United  States' appellee's submission, para.  145. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  appropriate benchmark under the covered agreements. Furthermore, in the United  States ' view, the 
question whether there is a measure that would better contribute to a particular objective is more 
pertinent to an analysis under Article  2.2 of the TBT Agreement , rather than under Article  2.1.435  
6.107.   We highlight that Mexico raises this argument in support of its view that the Panels erred in 
their evaluation of risk profiles, by relying on "setting on dolphins  in the ETP" as a "benchmark" by 
which to compare the risk profiles of different fisheries. However, as explained above, the Panels 
did not refer to the "ETP benchmark" in their analysis.436 Furthermore, based on our review of the 
Panels' findings, the Panel s did not compare, or "distinguish", the risk profile of "setting on dolphins 
in the ETP" with the risk profiles of all other individual fisheries. To the contrary, the Panels compared 
the risk profile of setting on dolphins as a fishing method (used anywh ere in the world) with the risk 
profiles of other fishing methods (also used anywhere in the world), in the context of examining the 
eligibility criteria437, and compared the risk profile of the ETP large purse seine fishery with other 
individual fisheries i n the context of examining the certification and tracking and verification 
requirements.438 Thus, the Panels did not compare the risk profile of the ETP setting -on-dolphins 
fishery with the risk profile of other fisheries. Since Mexico's argument is incorrec tly premised on 
the assertion that the Panels compared "setting on dolphins in the ETP" with other fisheries, we 
consider Mexico's argument to be moot.  
6.108.   In any event, we also note that Mexico's argument suggests that the Panels erred by failing 
to assess w hether certain individual fisheries should be ineligible for the dolphin -safe label. This 
argument appears to rely on Mexico's understanding that, in order to be properly calibrated, the 
eligibility criteria under the 2016 Tuna Measure must make distinctio ns on a fishery -by-fishery basis. 
We have addressed, and rejected, this argument above.439 As explained, the nature of the calibration 
analysis is defined by the nature of the regulatory distinctions under the measure itself.440 Since the 
eligibility criteria distinguish between different fishing methods, it would have been inappropriate for 
the Panels to compare the risk profiles of individual fisheries  for the purpose of assessing whether 
the eligibility criteria under the measure are properly calibrated. We therefore do not consider that 
this aspect of Mexico's arguments demonstrates that the Panels erred by comparing the risk profile 
of setting on dolphins with the risk profiles of other fishing methods in the context of examining the 
eligibility criteria. W e also reiterate that, in examining whether the certification and tracking and 
verification requirements are properly calibrated, the Panels were indeed required to compare the 
risk profiles of different fisheries.441 We examine whether the Panels properly c onducted this analysis 
in section 6.1.5 below.  
6.109.   Turning to Mexico's argument that the Panels erred by focusing their analysis on qualitative 
attributes that are unique to setting  on dolphins in the ETP , thereby "further ingraining" their mistake 
in adopting  the single "ETP benchmark" for the purpose of the calibration analysis442, we note that 
this argument relates to the Panels' findings on unobservable harms with respect to  "alleged stress 
effects on dolphins in the ETP".443 Specifically, Mexico considers that  the Panels emphasized different 
"kinds" of unobservable harms, which "caused them to disregard the Appellate  Body's direction to 
take into account the overall effects of each fishing method".444 Mexico highlights that, although the 
Panels referred to the ha rms caused by "ghost fishing" (whereby lost or discarded gillnets continue 
                                                
435 United  States' response to questioning at the hearing.  
436 See para. 6.103 above.  
437 See para. 6.67 above. In the context of determining the risk profile of setting on dolphins (anywhere 
in the world), the Panels relied to a significant extent on evidence related to the use of this fishing method in 
the ETP  in par ticular. (See supra , fn 406) Nevertheless, the Panels did not compare  setting on dolphins in the 
ETP – as a distinct fishery – with other fisheries. Rather, the Panels took into account the evidence regarding 
the ETP setting -on-dolphins fishery in assessin g the overall risk profile of setting on dolphins that the Panels 
proceeded to compare with the overall risk profiles of other fishing methods.  
438 See para. 6.67 above. The ETP large purse seine fishery refers to all purse seine fishing in the ETP by 
large purse seine vessels, including by setting on dolphins and by other means.  
439 See section 6.1.3.2 above.  
440 See para. 6.64 above.  
441 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.165.  
442 Mexico's appellant's submission, paras.  173 and 186.  
443 Mexico's appellant's submission, para.  187 (referring to Panel Reports, para.  7.310).  
444 Mexico's appellant's submission, para.  189 (referring to Appellate  Body Report, US – Tuna II 
(Mexico) (Article  21.5 – Mexico) , paras.  7.152 and 7.155 -7.156 ). WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  to cause harm to marine life, including dolphins445), the Panels concluded that such harms "are not 
the kind of unobservable harms caused by setting on dolphins".446  
6.110.   As explained above , in conducting their assessment of risk profiles for the purpose of the 
calibration analysis, the Panels distinguished between, inter alia, observable harm (any type of harm 
that can be detected and reported) and unobservable harm (the type of harm with respect to  which 
no evidence of its occurrence is produced during the set).447 In our view, drawing distinctions 
between different types of harm is not per se  inconsistent with an assessment of overall relative 
harm to dolphins for the purpose of the calibra tion analysis. Indeed, the Appellate  Body in the first 
compliance proceedi ngs also distinguished between observed harms and unobserved harms (the 
Panels referred to the latter as "unobservable" harms448) in setting forth the parties' disagreement 
over the ri sks associated with different fishing practices.449  
6.111.   Furthermore, the evidence examined by the Panels differed  depending on the specific type 
of harm being examined. With respect to  "observed" mortalities and significant injuries, the Panels 
tended to look a t quantitative evidence, primarily in the form of per set data, but also relying on 
other data when per set data w ere lacking.450 This included quantitative data in the form of absolute 
levels of mortalities and serious injuries as well as qualitative eviden ce where no quantitative 
information was available .451 By contrast, as indicated above, in assessing "unobserved but 
observable" harm (in other words, harm that could  be detected during a fishing set, but was  not 
detected), the Panels focused on the level of  association between dolphins and tuna as a proxy for 
evidence of such unobserved harm.452 Finally, in assessing "unobservable" harms, the Panels looked 
at evidence revealing the extent to which dolphins are harmed during a particular fishing operation 
even though no evidence of that harm is actually produced during the fishing operation itself.453  
6.112.   Given that the Panels were examining different types of evidence for each "type" of harm 
that they examined, we do not consider that the Panels erred merely by draw ing distinctions between 
different types of harm to dolphins. At the same time, we recall that the Appellate  Body in the first 
compliance proceedings faulted the first compliance panel, and found itself unable to complete the 
analysis, because the first co mpliance panel had focused its analysis exclusively on differences in 
unobserved harms, without comparing the overall  relative harms.454 Thus, in the present 
proceedings, if the Panels had focused exclusively on a particular "kind" of harm in assessing the 
overall relative harms of different fishing methods and fisheries, such an approach would not have 
comported with the nature of the required calibration analysis as articulated by the Appellate  Body. 
In this respect, we note that Mexico highlights the evide nce reviewed by the Panels regarding harms 
caused by "ghost fishing" in the context of gillnet and longline fishing, and contends that the Panels 
"omit[ ted] a comparative assessment" of such harms because the Panels considered that such harms 
are not the " kinds" of unobservable harms caused by setting on dolphins.455  
6.113.   In addressing this issue, we recall that the Panels found that "setting on dolphins" causes 
unobservable harms such as cow -calf separation, potential muscle injury resulting from the chase, 
immu ne and reproductive system  failures, and other adverse health consequences for dolphins, such 
as continuous acute stress.456 The Panels found that no other fishing method poses similar 
unobservable harms.457 We further note that the Panels discussed the impact  of ghost fishing 
specifically.458 The Panels ultimately considered that the harms posed to dolphins by ghost fishing 
were indeed relevant to their assessment of the risk profile of gillnet fishing, but that such harms 
were observable in nature in that they result from interaction with the fishing gear. The Panels 
explained that, although the harms from ghost fishing may not be observed, this "does not change 
                                                
445 See supra , fn 375.  
446 Mexico's appellant's submission, para.  188 (quoting Panel Reports, para.  7.450 (emphasis original)).  
447 See para. 6.85 above (referring to Panel Reports, paras.  7.245 -7.251).  
448 Panel Reports, para.  7.251.  
449 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.248.  
450 See e.g. Panel Reports, paras.  7.327 -7.332 and 7.434.  
451 See e.g. Panel Reports, paras.  7.170, 7.310, and 7.514.  
452 See e.g. Panel Reports, paras.  7.333 and 7.385. See also para. 6.85 above.  
453 See e.g. Panel Reports, paras.  7.289 -7.310.  
454 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.246 -7.251.  
455 Mexico's appellant's submission, para.  188. 
456 Panel Reports, para.  7.309.  
457 See e.g. Panel Reports, para.  7.525.  
458 Panel Reports, paras.  7.447 -7.450.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the observable nature of such harms", and that harms posed by ghost fishing "are not the kind of 
unobservable harms caused by setting on dolphins", because the latter "'may be inflicted even in 
cases where no dolphin is caught in the net, or where any caught dolphin is released without 
apparent injury'".459 The Panels nevertheless considered, with respect t o "observable harms to 
dolphins", that "gillnet fishing poses high levels  of observable harms to dolphins in certain areas of 
the ocean, but does not pose the same harms in other areas."460 The Panels considered that the 
same considerations applied with resp ect to  ghost fishing in the context of longline fishing461, and 
concluded, with respect to  observable harms caused by longline fishing, that "dolphins may suffer 
some observable mortality and serious injury as a result of [longline fishing] in some fisheries ."462 
Subsequently, when assessing whether the regulatory distinctions under the 2016 Tuna Measure are 
calibrated to different risks to dolphins, the Panels took into account all relevant types of harm in 
assessing and comparing different risk profiles.  
6.114.   In our view, the Panels' analysis is consistent with the requirement that they assess the 
"overall relative risks" to dolphins from different fishing methods as used in different ocean areas. 
Specifically, the Panels took into account ghost fishing in the cont ext of gillnet and longline fishing, 
and highlighted that certain gillnet fisheries pose a particularly high risk to dolphins, and that certain 
longline fisheries do cause observable mortalities and serious injuries to dolphins. The Panels also 
looked at s imilar observable harm to dolphins caused by setting on dolphins, as well as unobservable 
harms. The Panels relied on all such information when comparing the risk profiles of setting on 
dolphins with other fishing methods. We therefore consider that the Pa nels took into account all 
relevant types of harm in conducting an assessment of the overall relative risks from different fishing 
methods, as used in different fisheries, before reaching an overall conclusion regarding the risk 
profile of each fishing met hod.  
6.115.   We briefly note that aspects of Mexico's arguments relate solely to the Panels' appreciation 
of the evidence in their role as factfinder. Specifically, to the extent that Mexico considers that 
"the Panels relied [on] speculative hypotheses" and that "there is no conclusive evidence that dolphin 
sets … cause a material level of stress to dolphins"463, we consider that these aspects of Mexico's 
arguments pertain to the Panels' appreciation of the evidence.464 In the absence of any claim under 
Article  11 of the DSU, we consider that such arguments pertain to issues outside the scope of this 
appeal.  
6.116.   On the basis of the foregoing, we do not consider that Mexico has demonstrated that the 
Panels relied on the risk profile of setting on dolphins in the ETP as a be nchmark by which to assess 
different fishing methods. Additionally, we do not consider that Mexico has demonstrated that the 
Panels erred by distinguishing between different types of harm to dolphins.  
6.1.4.4   Whether the Panels erred by relying primarily on per s et data and excluding other 
relevant factors  
6.117.   We now turn to Mexico's arguments regarding the factors or methodology on which the 
Panels relied in assessing the risks of harm to dolphins. Mexico argues that, although the Panels 
were correct to rely on per s et data to assess the overall relative risks to dolphins, the 
Panel s' analysis was incomplete.465 In Mexico's view, "[a]ll factors that have a bearing on the 
measure achieving its objectives must be included" in order to properly measure the risks to 
dolphin s.466 Mexico  asserts that the Panels incorrectly omitted from their assessment: (i) the impact 
of tuna -fishing methods on the sustainability of dolphin stocks through Potential Biological Removal 
(PBR) data; (ii) data with respect to  absolute dolphin mortali ties and serious injuries in ocean areas; 
and (iii) data concerning the risks created in certain ocean areas through insufficient regulatory 
overs ight, unreliable reporting, IUU  fishing, and/or trans-shipment at sea.467 
                                                
459 Panel Reports, para.  7.450 (quoting First Compliance Panel Report, para. 7.134). (emphasis original)  
460 Panel Reports, para.  7.444.  
461 Panel Reports, para.  7.480.  
462 Panel Reports, para.  7.475.  
463 Mexico's appellant's submission,  fn 231 to para.  187. 
464 See supra , fn 405.  
465 Mexico's responses to questioning at the hearing.  
466 Mexico's appellant's submission, para.  193. See also ibid., paras. 192 and 194.  
467 Mexico's appellant's submission, para.  194. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.118.   The United  States  argues that the Panels were correct not to rely on the data to which Mexico 
refers.468 In the United  States ' view, Mexico's arguments concerning per set data are unsupported 
by any evidence and, in any event, relate to the Panels' appreciation of the eviden ce and are 
therefore outside the scope of this appeal in the absence of a claim under Article  11 of the DSU.469 
The United  States  also submits that the Panels' approach to PBR evidence , as well as to absolute 
levels of mortalities and serious injuries, was i n accordance with the approach taken by the 
Appellate  Body in prior proceedings in this dispute.470 The United  States  also considers that Mexico 
has not demonstrated that the Panels erred by failing to take into account a lack of regulatory 
oversight, or the  risks of inaccurate certification or tracking, in assessing the risks to dolphins.471 
6.119.   As an initial matter, we note that Mexico's arguments concern ing the Panels' reliance on 
per set data have evolved during these appellate proceedings. In its appellant's s ubmission, Mexico 
argued that the Panels' reliance on per set data was inconsistent, because the Panels disregarded 
such data for gillnet fisheries and trawl fishing, and relied on a "very small sample as the basis for 
[their] analysis of the risk profile of gillnet fishing".472 Mexico also stated that "[s]imilarly, although 
acknowledging that trawl fishing has resulted in significant dolphin mortalities, and the Panels 
identified a trawl fishery with a much higher per 1,000 set number than the ETP, they reli ed on 
anecdotal information to conclude that trawl fishing has a 'low -to-medium' risk profile."473 At the 
hearing, Mexico clarified that, in its view, the Panels did not err by including per set data in their 
assessment and did examine all evidence relating to per set data. Rather, Mexico argued, the Panels 
erred in excluding other relevant factors, and that , in order to properly apply the calibration analysis, 
an assessment of risks to dolphins should take into account all relevant factors, in order to captu re 
all aspects of adverse effects  on dolphins.474 
6.120.   In our view, Mexico's clarifications at the hearing indicate that it  is not challenging the 
Panels'  reliance on per set evidence per se . We therefore do not consider it necessary to address 
Mexico's arguments  concerning alleged errors in the Panels' reliance on per set evidence. In any 
event, to the extent that Mexico continues to assert that the Panels "disregarded" certain evidence, 
or that the Panels' "sample size" was too small with respect to  one particul ar fishing method, we 
consider that such arguments concern the Panels' appreciation of the evidence. Mexico has not 
claimed that the Panels' evaluation of per  set data was inconsistent with their obligation under 
Article  11 of the DSU to make an objective assessment of the matter before them. Consequently, 
we consider that arguments relating to such a claim fall outside the scope of this appeal.  
6.121.   We therefore address, in turn, Mexico's arguments that, in addition to  looking at per set 
evidence, the Panels al so should have taken into account: (i) evidence pertaining to the risks to 
dolphin populations in certain ocean areas; (ii) evidence of absolute levels of harm to dolphins in 
certain ocean areas; and (iii) evidence concerning lack of sufficient regulatory oversight in certain 
ocean areas.475 We note in this regard that Mexico does not argue on appeal that the Panels acted 
inconsistently with Article  11 of the DSU in making their assessment of different risk profiles.476 In 
the absence of such a claim, we limit our analysis below to the question whether Mexico has 
demonstrated that the Panels erred in applying Article  2.1 of the TBT Agreement , in making their 
assessment of different risk profiles.  
                                                
468 United  States' appellee's submi ssion, paras.  151-203. 
469 United  States' appellee's submission, paras.  162-174. 
470 United  States' appellee's submission, paras.  177-194 and 197 -198. 
471 United  States' appellee's submission, para.  202. 
472 Mexico's appellant's submission, para.  200. 
473 Mexico's a ppellant's submission, para.  200. The United  States argues that these aspects of Mexico's 
arguments pertain to the Panels' appreciation of the facts, and that, in any ev ent, the Panels did examine 
per set data for trawl fishing, and, with respect to gillne t fishing, the Panels relied on per set data as far as 
possible and relied on other evidence when per set data were not available. (United  States' appellee's 
submission, paras.  167-173 (referring to Panel Reports, paras.  7.433 -7.434, 7.441 -7.443, and  7.489 -7.494))  
474 Mexico's response to questioning at the hearing.  
475 At the hearing, Mexico clarified that it is arguing that PBR evidence should have been taken into 
account in addition to per set evidence, and that all relevant factors should have been taken in to account.  
476 Mexico does raise a claim under Article  11 of the DSU pertaining to the Panels' assessment of 
whether the 2016 Tuna Measure is adequately calibrated to different risks to dolphins. We address this claim in 
section 6.1.5.4 below.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.1.4.4.1   Risks to dolphin populations  
6.122.   Mexico argues that, in addition to looking at per set evidence, the Panels also  should have 
taken into account evidence pertaining to dolphin sustainability in certain ocean areas, specifically 
evidence reflecting PBR levels. Mexico notes that PBR levels indicate the "maximum number of 
animals, not including natural mortalities, that may be removed from an animal stock (such as 
dolphins) while allowing that stock to reach or maintain its optimum sustainable population".477 In 
Mexico's view, the Panels erred by failing to take into account PBR evidence that shows high risks 
to dolphin populations in certain ocean areas, because, in Mexico's view, such risks to dolphin 
populations are relevant to an assessment of the overall relative risk profiles of certain fisheries.478 
Mexico considers that this view is supported by the findings of the original panel concerning adverse 
effects to dolphins479, findings by the first compliance panel concerning the objective of the 
measure480, and the design and structure of the 2016 Tuna Meas ure.481  
6.123.    In the United  States ' view, the Panels' decision to disregard PBR evidence was in accordance 
with both the design and structure of the measure, as well as relevant prior findings by previous 
panels and the Appellate  Body in this dispute.482 The Unite d States  highlights, and agrees with, the 
Panels' finding that the objective of the measure is primarily to protect individual dolphins, and that 
a PBR methodology is focused on the effect that dolphin mortalities have on a dolphin stock, rather 
than the a ctual likelihood of dolphins being adversely affected.483 To the extent that dolphin 
sustainability may be an objective of the measure, the United  States  maintains that it is indirect 
(i.e. "due to a relationship between reducing 'adverse effects' on individ ual dolphins and conserving 
dolphin populations").484 The United  States  submits that the Panels fully explained their decision not 
to rely on a PBR methodology485, and argues that Mexico has not challenged under Article  11 of the 
DSU the Panels' factual findin g that the measure  at issue  is concerned more with the risks to 
individual dolphins than the risks to dolphin populations.486 
6.124.   The Panels found that PBR evidence reveals "the maximum possible number of animals, in 
this case dolphins, which can be removed from  an animal stock without affecting the population or 
its sustainability".487 The Panels considered that a PBR  methodology is "suitable in the context of 
policies that concern the sustainability of marine mammal stocks and where a certain level of 
mortalities  or serious injury is tolerated".488 The Panels considered that "there is no part icular 
indication that the Tuna  Measure is directly concerned with the protection of the population levels of 
dolphins" and that, while "mortality or serious injury suffered by individual dolphins may also have 
population -level consequences[,] … [t]hat, however, is not directly relevant to the findings that [they 
would] make about the overall levels of relative risks posed to dolphins by different fishing methods 
                                                
477 Mexico's ap pellant's submission, para.  202 (referring to Panel Reports, para. 7.184 and fn 328 
thereto).  
478 Mexico's appellant's submission, paras.  202 and 211.  
479 Mexico's appellant's submission, paras.  207 and 209 (referring to Original Panel Report, 
paras.  7.419 -7.420, 7.433, 7.485 -7.486, 7.490, 7.550 -7.552, 7.562, 7.574, 7.600, 7.621, 7.718, and 7.726).  
480 Mexico's appellant's submission, para.  210 (quoting First Compliance Panel Report, para.  7.528, in 
turn referring to Original Panel Report, paras. 7.485 -7.486).  
481 Mexico's appellant's submission, paras.  212-213. 
482 United  States' appellee's submission, paras.  177-184. 
483 United  States' appellee's submission, para.  178 (referring to Panel Reports, paras.  7.186 -7.190 
and 7.473). The United  States notes that, under a PBR methodology, "huge numbers of dolphin mortalities in 
one fishery may be tolerated while de minimis levels in another are deemed unacceptable." (Ibid.) The 
United  States highlights findings by the Appellate  Body in the first compliance proceedings that the calibration 
analysis relates to the "likelihood that dolphins would be adversely affected in the course of tuna fishing 
operations in different fisheries". (Ibid., para.  179 (quoting Appellate  Body Report, US – Tuna II (Mexico) 
(Article  21.5 – Mexico) , para. 7.157; referring to paras.  7.101, 7.110, 7.122, 7.157, 7.162, 7.239, 
7.245 -7.251, 7.288, 7.325, and 7.330)) In the United  States' view, the original panel's reference to "dolphin 
populations" s hould be read as referring to "risks to groups of dolphins in different areas" rather than risks to 
dolphin stocks, and this is "confirmed" by relevant findings of the Appellate  Body in the original proceedings. 
(Ibid., paras.  181-182) 
484 United  States' app ellee's submission, para.  183 (referring to Original Panel Report, 
paras.  7.419 -7.420, 7.485 -7.486, 7.490, 7.550 -7.551, and 7.528).  
485 United  States' appellee's submission, paras.  185-189 (referring to Panel Reports, paras.  7.186, 
7.188 -7.189, 7.469, and 7. 473).  
486 United  States' appellee's submission, paras.  191-192 (referring to Panel Reports, 
paras.  7.186 -7.187).  
487 Panel Reports, para.  7.184.  
488 Panel Reports, para.  7.184.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  in different are as of the ocean."489 The Panels highlighted that , "[b]y allowing the existence of some 
dolphin mortalities and focusing primarily on the population levels, the PBR methodology prioritizes 
the sustainability of the population rather than the well -being of ind ividual dolphins", which would 
be "difficult to reconcile with the objectives of the Tuna Measure".490 The Panels also noted that "the 
architecture of the measure … by its own terms is concerned with the mortality and serious injury 
of individual dolphins, o n a per set basis, rather than with the overall sustainability of dolphin 
stocks ."491 
6.125.   We observe that Mexico has not made any claims under Article  11 of the DSU regarding the 
Panels' appreciation of the facts, and that Mexico has clarified that its argument with respect to  
PBR evidence relates to the Panels' omission of a relevant "factor"492 or "methodology"493 in their 
assessment of risk profiles. The legal issue before us is therefore whether the Panels erred in their 
application of Article  2.1 of the TBT Agreement  by declining to take into account PBR evidence in 
assessing and comparing the risk profiles of different fishing methods and fisheries for the purpose 
of the calibration analysis.  
6.126.   We recall that, in order to properly conduct the calibration analysis, the Panels were required 
to assess the overall relative risks of different fishing methods and fisheries.494 Furthermore, the 
purpose  of this analysis was to assess whether the detrimental impact from the 2016 Tuna Measure 
stems exclusively from a legitimate regulatory distinction. As our analysis above reveals, the nature 
of the calibration analysis, including the relevant risks to be assessed , is informed by  the nature of 
the relevant regulatory distinctions causing the detrimental impact.495  
6.127.   Under  the 2016 Tuna Measure, a tuna product is ineligible for the label if it contains tuna 
"caught in a set or gear deployment in which dolphins were killed or seriously injured".496 
Furthermore, the 2016 Tuna Measure "is generally applied on a per gear deployme nt basis in respect 
of how often captains have to make non -dolphin safe certifications , or how frequently 
non-dolphin  safe tuna must be segregated from dolphin -safe tuna ."497 Thus, the relevant regulatory 
distinctions made by the measure itself apply on a pe r set basis. Based on the design and structure 
of the measure, we agree with the Panels that the dolphin -safe label is concerned  with the well -being 
of individual dolphins, and that the design and structure of the relevant regulatory distinctions reveal 
that the relevant risks to dolphins, for the purpose of the calibration analysis, are the risks of 
individual dolphins being killed or seriously injured in the fishing process.498  
6.128.   We note Mexico's argument that the Panels' characterization of the Tuna M easure  as "'mainly 
concerned with the risks facing dolphins at an individual level, rather than at a population level', is 
flatly contradicted by the measure itself".499 In Mexico's view, this is because the 2016 Tuna Measure 
expressly contemplated that the prohib ition on the use of the dolphin -safe label for tuna derived 
from setting on dolphins could be removed following "an evaluation of the potential impact of dolphin 
sets on the populations of the dolphin stocks in the ETP".500 In our view, however, the 
Panels'  understanding of the measure as "mainly concerned with the risks facing dolphins at an 
                                                
489 Panel Reports, para.  7.186.  
490 Panel Reports, para.  7.188.  
491 Panel Reports, para. 7.190.  
492 Mexico's appellant's submission, para.  202. 
493 Mexico's appellant's submission, para.  204. 
494 See e.g. para. 6.81  above.  
495 See e.g. para. 6.64 above.  
496 Panel Reports, para.  7.190.  
497 Panel Reports, para.  7.213.  
498 Panel Reports, para.  7.190. The  Panels also explained that the 2016 Tuna Measure is concerned with 
"the protection of the well -being of dolphins, and with informing consumers whether the tuna used in the 
production of particular tuna products was caught in a set that harmed dolphins". ( Ibid., para.  7.186)  
499 Mexico's appellant's submission, para.  214 (quoting Panel Reports, para. 7.473). (emphasis omitted)  
500 Mexico's appellant's submission, para.  214 (referring to Original Panel Report, para.  2.16). 
Section  1385(g) of the DPCIA requires t he Secretary of Commerce to make a finding regarding whether setting 
on dolphins "is having a significant adverse impact on any depleted dolphin stock in the [ETP]". 
Section  1385(h)(2) further requires that the certification requirements regarding tuna cau ght by large purse 
seine vessels in the ETP are inapplicable if the Secretary of Commerce determines that setting on dolphins is 
not having a significant adverse impact on depleted dolphin stock in the ETP. (See Original Panel Report, 
para. 2.16; Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , fn 127 to para. 6.9. See also 
DPCIA (Panel Exhibits MEX -1 and USA -1)) As noted in paragraph 5.10 above, although the Secretary of 
Commerce made such a determination, it was overturned by the Hogarth ruling.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  individual level"501 does not suggest that the risks to dolphin populations are irrelevant, or that the 
2016 Tuna Measure is not at least indirectly concerned with protect ing dolphin populations. We see 
no reason to disagree with the Panels' finding that "mortality or serious injury suffered by individual 
dolphins may also have population -level consequences ."502 We recall the original panel's findings 
that "the adverse effect s on dolphins targeted by the US  dolphin -safe provisions, as described by 
the United  States , relate to observed and unobserved mortalities and serious injuries to individual 
dolphins in the course of tuna fishing operations" and that "the US  objectives als o incorporate, at 
least indirectly, considerations regarding the conservation of dolphin stocks ."503 On this basis, we 
also disagree with Mexico's argument that, because the dolphin -safe labels are granted under 
conditions that primarily take into account the risks to individual dolphins, consumers are misled 
and deceived about whether or not the tuna th at they are purchasing was caught in a manner that 
threatens or endangers dolphin populations.504  
6.129.   We recall Mexico's argument that, if the measure is truly concerned with the protection of 
individual dolphins, any "fishing method that is capable of harming a dolphin should be ineligible" 
for the dolphin -safe label.505 As explained above, we consider that the 2016 Tuna Measure will not 
violate Article  2.1 if the relevant regulatory distinctions leading to detrimental impact are properly 
"calibrated" to the risk s to dolphins arising from different fishing methods in different areas of the 
oceans.506 Furthermore, if it can be shown that the distinctions are calibrated to different risks to 
dolphins, this would also indicate that such distinctions are rationally rela ted to, and hence capable 
of contributing to, the measure's objectives.507 In our view, the fact that the 2016 Tuna Measure 
grants  a dolphin -safe label to certain fishing methods that may be capable of harming a dolphin does 
not imply that the 2016 Tuna Meas ure is not concerned with informing consumers of the risks to 
individual dolphins.  
6.130.   Thus, we agree with the Panels that the essential question for the purpose of assessing the 
calibration of the 2016 Tuna Measure is whether the relevant regulatory distinct ions are calibrated 
to different risks that dolphins will be killed or seriously injured in the process of harvesting tuna.508 
It is uncontested that PBR evidence does not reveal the likelihood of dolphins being killed or seriously 
injured in a particular fi shing operation.509 Rather, it indicates the number of dolphins  that can be 
safely removed without jeopardizing the sustainability of the dolphin population as a whole.  
6.131.   We recall that, before the Panels, Mexico contended that the Panels should have adopted 
the PBR methodology, rather than  the per set methodology, in assessing the risks to dolphins.510 On 
appeal, Mexico acknowledges the utility of per set evidence where dolphin mortalities per set are 
high, but challenges the Panels' reliance on per set evidenc e in circumstances in which PBR evidence 
indicates that even a low level of mortalities per set would endanger the dolphin population of a 
fishery.511 However, Mexico has not explained how reliance on PBR evidence  in these circumstances 
relates to, or reveal s, the actual  risks that dolphins were killed or seriously injured in the fishing 
process. Thus, as noted by the Panels, relying on PBR evidence would have resulted in an assessment 
of a different  kind of risk to dolphins than the risks of which the measur e seeks to inform 
consumers.512 We therefore agree with the Panels' assessment that the PBR methodology prioritizes 
the sustainability of the population in a way that would have prevented the Panels from adequately 
assessing whether the measure is calibrated  to different risks that a dolphin was harmed or killed in 
                                                
501 Panel Reports, para.  7.473. (emphasis omitted)  
502 Panel Reports, para.  7.186.  
503 Original Panel Report, para.  7.486. The first compliance panel also found that "there is an essential 
and inextricable link between the protection of dolphins on a n individual scale and the 'replenishment of [an] 
endangered species', for it is only through protecting individual dolphins that a population itself can be 
protected, replenished, and maintained ." (First Compliance Panel Report, para.  7.527 (quoting Appel late Body 
Reports, China – Rare Earths , para. 5.89))  
504 Mexico's response to questioning at the hearing.  
505 Mexico's appellant's submission, para.  216. 
506 See para.  6.36 above.  
507 See para.  6.74 above.  
508 Panel Reports, para.  7.186.  
509 In contrast, per set evide nce, revealing the risk of a dolphin being injured in any individual set , is 
indeed a relevant and useful measure of the risk that dolphins are killed or seriously injured in the fishing 
process. (Panel Reports, para.  7.204)  
510 Panel Reports, para.  7.175 (s tating that "[f]or Mexico, the use of the PBR methodology would 
capture all of the relevant factors that need to be taken into account by the Panels").  
511 Mexico's appellant's submission, para.  215; responses to questioning at the hearing.  
512 Panel Reports, paras.  7.186 -7.190.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the fishing process, and that "the PBR methodology … sits uncomfortably with the design and 
structure of the 2016 Tuna Measure ."513  
6.132.   Mexico further maintains that its position comports with the Appel late Body's statement in 
the first compliance proceedings that it did "not exclude that reference to … objective indicators 
[such as PBR evidence ] might assist in an assessment of whether regulatory differences in the 
treatment of different fisheries can b e 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" .514 This statement by the Appellate  Body acknowledging the possible 
relevance of PBR evidence does not state that a panel is necessarily required to rely on such evidence 
as an objective indicator or means of assessing whether the measure is properly calibrated. To the 
contrary, the Appellate  Body avoided taking a position on that issue and explained that a panel 
should rely on evidence reflecting appropriate objective indicators in assessing the risks to dolphins. 
In our view, the Panels adequately explained their decision to rely primarily on per set evidence, 
and not PBR evidence, in accordance with the Appellate  Body's guidance to rely on objective 
indicators.  
6.133.   Additionally, we recall Mexico's assertion that the Panels arbitrarily included, within their 
analysis, "unobservable harms 'whose realization cannot be definitely  established'" and excluded 
"measured and realized harms that threaten the sustainability of entire dolphin populations in areas 
of the oceans".515 We consider that the appropriate "measured and realized harms" that the Panels 
were obliged to take into accou nt were the risks of harm to individual dolphins (e.g. mortality and 
serious injury) , which the Panels did  take into account in their reliance on per set evidence.516 In the 
same vein, we also disagree with Mexico's assertion that the Panels did not explain how the use of 
a fishing method that causes or threatens dolphin population collapse could not be considered as 
"adversely affecting dolphins".517 Rather, the Panels explicitly recognized "that mortality or serious 
injury suffered by individual dolphins may also have population -level consequences ."518 
Furthermore, as indicated above, we agree with the Panels that the protection of individual dolphins 
can indeed contribut e to the conservation of dolphin populations.  
6.134.   For these reasons, we consider that Mexico has not demonstrated that the Panels erred in 
applying Article  2.1 by not taking into account PBR evidence when assessing the overall relative 
risks to dolphins of di fferent fishing methods in different ocean areas. This is not meant to  imply 
that the Panels failed to take into consideration risks to dolphin populations. Rather, we understand 
the Panels to have considered that the 2016 Tuna Measure seeks to protect dol phin populations by 
protecting individual dolphins and , consequently , their analysis focused on evidence revealing the 
risks that individual dolphins are harmed or killed in the fishing process. In our view, this approach 
is consistent with the nature of t he calibration analysis the  Panels  were required to undertake.  
6.1.4.4.2   Absolute levels of adverse effects  
6.135.   Mexico argues that the Panels erred by failing to compare the absolute levels of mortalities 
and serious injuries to dolphins in different fisheries. Mexico explains that, in fisheries with many 
sets, the "overall" adverse effects will be "masked" by the per set data, such that "tuna caught in 
an ocean area where tuna fishing is causing tens of thousands of deaths per year could be found 
eligible for the dolph in-safe label ."519 To Mexico, these absolute levels of adverse effects constitute 
"'overall adverse effects on dolphins' for the fishing method/area".520 Mexico argues that "fishing 
practices in such ocean areas should be discouraged"521, and that "the omission of these overall 
adverse effects contradicts the two objectives of the measure ."522  
6.136.   In the United  States ' view, a comparison of absolute levels of adverse effects fails to take 
into account unobservable harms, and does not "'contextualize' the adverse effec ts on dolphins in 
                                                
513 Panel Reports, para.  7.190.  
514 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , fn 827 to para.  7.251.  
515 Mexico's appellant's submission, para.  212 (quoting Panel Reports, para.  7.544).  
516 Panel Reports, paras.  7.186 -7.191, 7.204 -7.214, and 7.251.  
517 Mexico's appellant's submission, para.  213. 
518 Panel Reports, para.  7.186.  
519 Mexico's appellant's submission, para.  218. 
520 Mexico's appellant's submission, para.  218. 
521 Mexico's appellant's submission, para. 218. 
522 Mexico's appellant's submission, para. 219.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  different fisheries", given the different sizes and effort levels of fisheries.523 The United  States  
explains that "a fishery with a few vessels would be compared directly with a fishery comprising 
thousands of vessels" and the "'absolute' numbers of dolphin mortalities might be greater in the 
second fishery, even if dolphins were hardly ever killed or even seen in the fishery, simply due to its 
far greater size."524 The United  States  also points out that Mexico has "never defined or explained  
the 'ocean regions' or 'fisheries' that should be assessed", but has "consistently compared the 
dolphin mortalities caused by the 80 -90 vessels setting on dolphins with those caused by thousands 
of other vessels around the world", which "perversely" disto rts the comparison, since setting on 
dolphins "has been banned almost everywhere in the world".525 
6.137.   We note as an initial matter that the Panels did not completely exclude evidence of absolute 
levels of dolphin mortalities and serious injuries. Rather, the Pa nels opted to rely on such evidence 
in assessing certain fishing methods and fisheries where they considered that the available per set 
evidence was lacking.526 Furthermore, Mexico has not identified any specific evidence of absolute 
levels of mortalities or  serious injuries that the Panels disregarded. We also note that calculating 
levels of harm on a per set basis necessarily takes into account absolute levels of harm as part of 
the calculation.527 We therefore understand that Mexico's argument pertains not t o the Panels' 
"rejection" of such "absolute" evidence, but to the Panels' decision to rely on per set evidence, rather 
than absolute evidence, as their primary methodology  by which to assess and compare the risks to 
dolphins.528  
6.138.   The Panels opted not to rely  primarily on evidence of absolute levels of dolphin mortalities 
and significant injuries, on the basis that:  
[S]uch a methodology would not necessarily deal with the issue of how to compare the 
levels of adverse effects on dolphins arising from different fishing methods in different 
areas of the ocean, or contextualize them in the light of the relative extent and  
intensity to which different fishing methods are use d, in such a way as to allow 
an apples -to-apples  assessment of the relative harmfulness of different fishing methods 
as used in different areas of the oceans.529 
6.139.   As explained above530, an assessment as to whether the 2016 Tuna Measure is consistent 
with Article  2.1 of the TBT Agreement  calls for a n analysis  of the overall relative risks to dolphins.531 
The Panels were therefore required to use a metric, or methodology, that allowed for a proper 
comparison of risks to dolphins across fisheries. In light of the relative  nature of the comparison to 
be undertaken,  we agree with the Panels that any comparison of risks to dolphins in different tuna 
fisheries should, in principle, be an "apples -to-apples" comparison, such that relevant differences 
between the fisheries are appropriately taken into account.532 We also no te the Panels' findings that 
the "extent and intensity to which different fishing methods are used" varies from fishery to 
fishery.533  
6.140.   The Panels considered that data reflecting the number of absolute dolphin mortalities or 
serious injuries in a particular fishery do not account for such differences. In the Panels' view, 
absolute levels of mortalities or serious injuries present a number that is independent of the specific 
                                                
523 United  States' appellee's submission, para.  198 (quoting Panel Reports, para.  7.195).  
524 United  States' appellee's submission, para.  198. 
525 United  States' appellee's submission, para.  199. (fn omitted)  
526 See e.g. Panel Reports, paras.  7.434, 7.438, 7.441, and 7.467.  
527 As the Panels explained, "a per set or per gear deployment comparison entails averaging some of the 
relevant indicators identified in paragraph 7.169 [of the Panel Reports], including observe d mortalities, serious 
injuries, and interactions, by the number of operations of the fishing gear used in a particular fishery in a given 
time period." (Panel Reports, para.  7.204)  
528 Mexico has not argued that the Panels' appreciation of the evidence was inconsistent with Article  11 
of the DSU, and we therefore proceed by assessing only whether the Panels' primary reliance on per set 
evidence was inconsistent with the legal standard under Article  2.1 of the TBT  Agreement.  
529 Panel Reports, para.  7.195. (emp hasis original)  
530 See e.g. para. 6.38 above.  
531 See also Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.169, 7.229, 
and 7.248. The Appellate  Body emphasized in the first compliance proceedings the "relational and comparative 
nature of the analysis of whether the amended measure is calibrated and even -handed" under Article  2.1 of 
the TBT Agreement. (Ibid., para.  7.126)  
532 Panel Reports, para.  7.195. (emphasis added)  
533 Panel Reports, para.  7.195. See also ibid., para.  7.204.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  features of the fishery (for instance, the number of fishing operations conducted per year in that 
fishery).534 The Panels stated that "such a methodology would not necessarily … allow an 
apples -to-apples  assessment of the relative harmfulness of different fishing methods as used in 
different areas of the oceans."535 In contrast, the Panels fou nd that the per set methodology, which 
entailed "averaging" the total number of a particular indicator of adverse effects536 to dolphins by 
the number of operations of a particular type of fishing gear used in a particular fishery in a given 
time period, would "control for the intensity of a given fishing operation in a given area of the 
ocean".537  
6.141.   Furthermore, it is uncontested, as the Panels found, that the 2016 Tun a Measure 
"is generally applied on a per gear deployment basis in respect of how often capt ains have to make 
non-dolphin safe certifications, or how frequently non -dolphin safe tuna must be segregated from 
dolphin -safe tuna".538 As we have explained above, we understand that the regulatory distinctions 
drawn under the measure are intended to addre ss the risks that dolphins were killed or seriously 
injured in the fishing process.539 In our view, a proper examination as to whether such distinctions 
are calibrated to the relevant risks to dolphins should take into account the relevant differences 
across  fisheries. The Panels' reasoning as set forth above indicates tha t a per set methodology is 
well suited to the kind of comparative analysis that Article  2.1 required the Panels to perform in this 
dispute. The Panels' factual findings also demonstrate that  a comparison of absolute levels of 
mortalities or serious injuries would be less likely to reveal the relative likelihood of a dolphin being 
killed or injured in the fishing process than a comparison of per set data.540  
6.142.   We recall Mexico's argument that "ov erall" adverse effects will be "masked" by the per set 
data, and that the absolute levels of adverse effects constitute "'overall adverse effects on dolphins' 
for the fishing method/area".541 In the first compliance proceedings, the Appellate  Body faulted th e 
panel for not examining all  relevant relative risks of harm to dolphins, including both observed and 
unobserved harm s.542 Thus, an assessment of the overall  relative risks to dolphins requires a panel 
to assess all relevant risks of harm to dolphins. We do  not discount that, depending on the particular 
evidence provided to the Panels, evidence of absolute levels of adverse effects might indeed be 
useful in this regard. However, as explained above, the Panels were not only required to assess the 
overall  risks, but the overall relative risks to dolphins.543 As indicated above, comparing absolute 
levels of mortalities or serious injuries across different fisheries would not take into account 
important differences between those fisheries. By contrast, a comparison  of per set data does indeed 
take into account such differences.544  
6.143.   For these reasons, we consider that Mexico has not demonstrated that, in deciding to rely 
primarily on a per set methodology  rather than comparing absolute levels of harm, the Panels acted 
inconsistently with the requirement to assess the overall relative risks to dolphins from different 
fishing methods and fisheries.  
                                                
534 Panel Reports, paras.  7.195 and 7.204.  
535 Panel Reports, para.  7.195. (emphasis original)  
536 These include observed mortalities, serious injuries, and interactions with dolphins of the fishing 
method in a given area of the ocean. (Panel Reports, paras.  7.169 a nd 7.204)  
537 Panel Reports, para.  7.204. We note that this tension between per set evidence and "absolute" 
evidence was demonstrated in the Panels' assessment of longline fishing, with respect to which Mexico 
presented evidence of high levels of absolute an nual mortalities in the Pacific Ocean. (Ibid., para.  7.467) The 
Panels declined to accord much weight to this data, on the basis that the data reflected many different longline 
fisheries, and relevant per set data for certain individual longline fisheries covered by the absolute data 
revealed a low rate of dolphin interactions. (Ibid., para.  7.468)  
538 Panel Reports, para.  7.213.  
539 See para. 6.127 above.  
540 Panel Reports, para.  7.195.  
541 Mexico's appellant's submission, para.  218. 
542 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.161.  
543 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.169, 7.229, 
and 7.248.  
544 See Panel Reports, para.  7.204. Notwithstanding that such absolute levels of harm are less hel pful in 
comparing the risks to dolphins for the purpose of the calibration analysis, we see no reason for the Panels not 
to rely on such evidence in assessing the risks to dolphins in situations where the relevant per set evidence 
was lacking.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.1.4.4.3   Insufficient regulatory oversight  
6.144.   Mexico argues that the Panels erred by omitting evidence of insufficient regulatory oversi ght 
in certain ocean areas, because "dolphins will be at a greater relative risk of harms from … fishing 
method[s used] in ocean areas that have insufficient regulatory oversight including unreliable 
reporting, significant IUU fishing and/or significant tr anshipment at sea than in ocean areas that do 
not."545 In Mexico's view, the omission of the "reliability of reporting as a criterion in the risk profiles 
of the fishing areas contradicts the objectives of the measure".546 Mexico explains that, in 
"unreliable"  fisheries there is a "greater risk that adverse effects  on dolphins will be 
unreported  … and, therefore, that actions that adversely affect dolphins in unreliable fisheries will 
not be discouraged by the measure".547 
6.145.   The United  States  considers that Mexico ma kes two distinct arguments: (i)  insufficient 
regulatory oversight causes greater ris k of harm to dolphins; and (ii)  insufficient regulatory oversight 
should be included in the risk profiles of fisheries "because it can affect the r eliability of reporting of 
harms to dolphins".548 The United  States  considers that it fully addressed Mexico's first argument in 
the context of Mexico's claim that the Panels erred in their interpretation of Article  2.1 of the 
TBT Agreement .549 As to Mexico's second argument, the United  States  highlights that this argument 
was "fully considered and rejected by the Panels", and argues that the Panels correctly explained 
that the risks of inaccuracy are not themselves risks of harm to dolphins.550 In the 
United  States ' view, such risks of inaccuracy rather "may be relevant to assessing whether the 
distinctions of the 2016 measure are calibrated to the risk profiles of different fisheries".551 
6.146.   As explained above552, the question whether the relevant regulatory distinctions under the 
2016 Tuna Measure are properly calibrated to different risks to dolphins does not  require assessing 
whether the 2016 Tuna Measure is also calibrated to the "risk of inaccuracy". As discussed in 
paragraph 6.51 above, Mexico has not su bstantiated its assertion that tuna fishing in ocean areas 
with less reliable regulatory systems is more likely to lead to harm to dolphins.553 We therefore see 
no reason to disagree with the Panels' statement that "the risks of inaccurate certification, rep orting, 
and/or record -keeping are not risks that affect dolphins themselves ."554  
6.147.   As noted, the Panels did not exclude the possibility that factors such as a lack of regulatory 
oversight may affect the accuracy of the label.555 We have explained above that suc h risks of 
inaccuracy are relevant to the assessment of whether the measure is calibrated to the risks to 
dolphins.556 It was, however, incumbent upon Mexico to provide relevant evidence in support of its 
argument that a lack of regulatory oversight in a fis hery will increase the risk that labelling of tuna 
                                                
545 Mexico's appellant's submission, para.  220. 
546 Mexico's appellant's submission, para.  223 (referring to Panel Reports, paras. 7.186 and  7.705).  
547 Mexico's appellant's submission, para.  223. 
548 United  States' appellee's submission, para.  202. 
549 United  States' appellee's submission, para.  202. See also paras. 6.47 -6.50 above. The United  States 
argued in that context that, contrary to Mexico's preferred approach, the Panels' approach was consistent with 
the Appellate  Body's guidance in the first compliance procee dings. (Ibid., paras.  47-50) The United  States also 
argued that Mexico's approach implies that the Panels should have applied a different type of calibration 
analysis to the certification and tracking and verification requirements than to the eligibility c riteria, and that 
Mexico has never argued as a factual matter that dolphins are at a greater risk of harm in areas where the 
reliability of applicable systems is low. (Ibid., paras.  51-53) 
550 United  States' appellee's submission, para.  202 (referring to Pan el Reports, paras.  7.109 -7.113 
and 7.119 -7.124).  
551 United  States' appellee's submission, para.  202 (referring to Panel Reports, paras.  7.119 -7.124).  
552 See section 6.1.3.1 and para. 6.79 above.  
553 We further note that Mexico has not argued that the Panels er red under Article  11 of the DSU by 
omitting specific evidence of a heightened risk to dolphins in any particular fishery in their examination of risks 
to dolphins in different fisheries.  
554 Panel Reports, para.  7.110. Although Mexico has described its argum ents on appeal as relating to 
"insufficient regulatory oversight", we note that Mexico specifically takes issue with the Panels' findings with 
respect to "inaccurate certification, reporting, and/or record -keeping". (Mexico's appellant's submission, 
paras.  220-222) We therefore see no distinction between Mexico's references to "regulatory oversight" and the 
Panels' discussion of "inaccurate certification, reporting, and/or record -keeping".  
555 See para. 6.52 above.  
556 See para. 6.52 above.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  products containing tuna caught in such a fishery will not accurately reflect the dolphin -safe nature 
of the tuna. We address this issue in  section 6.1.5 below.  
6.1.4.5   Conclusion  
6.148.   In conducting their examination of the risk profiles of different fishing methods as used in 
different ocean areas, the Panels reviewed  all relevant evidence of risks to dolphins as provided to 
them by the parties, including all evidence pertaining to individual fisheries. Additionally, the Panels 
appropriately took into account all relevant types of harm to dolphins in assessing the risk profiles 
of different fishing methods and fisheries. Moreover, the Panels did not err in relying on per set data 
as the primary measurement of the risks  to dolphins, despite three additional measurements 
proposed by Mexico. First, because the relevant risks to be assessed for the purpose of calibration 
are the risks of individual dolphins being harmed or killed in the fishing process, the Panels were 
correct not to rely on PBR evidence to assess the risks to dolphins. Second, given the comparative 
nature of the calibration analysis, the Panels did not err by relying primarily on a per set methodology 
instead of a comparison of absolute levels of harm. Fina lly, Mexico did not substantiate its assertion 
that tuna fishing in ocean areas with less reliable regulatory systems is more likely to lead to harm 
to dolphins, and therefore the Panels did not err by excluding evidence pertaining to regulatory 
oversight from their assessment of the overall relative risks to dolphins from the use of different 
fishing methods as used in different areas of the ocean. We therefore find no error in the 
Panels'  assessment of the risks to dolphins arising from the use of differe nt fishing methods in 
different ocean areas or in their conclusions regarding the risk profiles of relevant fishing methods 
on the basis of that assessment.  
6.1.5   The Panels' assessment of whether the 2016 Tuna Measure is calibrated  to the risks 
to dolphins  
6.1.5.1   Introduction  
6.149.   As noted above, in assessing whether the detrimental impact caused by the 2016  Tuna 
Measure stems exclusively from a legitimate regulatory distincti on, the Panels examined whether  
(i) the eligibility criteria; (ii)  the certif ication requirements; (iii) the tracking and verification 
requirements; and (iv)  the deter mination provisions of the 2016  Tuna Measure are calibrated to the 
difference in the overall risks to dolphins arising from the use of different fishing methods in different 
areas of the o cean.557 After concluding their intermediate analyses of these component elements of 
the 2016 Tuna Measure, the Panels "synthesize[d]" their analysis in order to reach their conclusion 
as to the consistency of the 2016 Tuna Measure with the TBT Agreement .558 Following their analyses, 
the Panels came  to the "general conclusion " that: 
[T]he 2016  Tuna Measure, as a whole, is calibrated to the risks to dolphins arising from 
the use of different fishing methods in different areas of the ocean. Therefore, the Panel s 
find that the distinctions made by that Measure between setting on dolphins and the 
other fishing methods (except, of course, high seas driftnet which is also disqualified 
from the dolphin -safe label) stem exclusively from legitimate regulatory distincti ons. 
Consequently, the Panels conclude that the 2016  Tuna Measure accords to Mexican tuna 
products treatment no less favourable than that accorded to like products from the 
United  States  and other countries, and therefore is consistent with Article  2.1 of the 
TBT Agreement.559 
6.150.   On appeal, Mexico requests us to reverse several of the intermediate findings that led to the 
above "general conclusion" by the Panels, which Mexico also contests.560 Specifically, Mexico 
challenges the Panels' assessment of the following  aspects of  the 2016  Tuna Measure: 
(i) the eligibility criteria; (ii)  the certif ication requirements; (iii)  the tracking and verification 
                                                
557 Panel Reports, par a. 7.530. See also ibid., paras.  7.547, 7.611, 7.676, 7.702, and 7.704.  
558 Panel Reports, para.  7.530 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.21). See also ibid., paras.  7.703 -7.716.  
559 Panel Reports, para . 7.717.  
560 Mexico's Notice of Appeal, para.  9; appellant's submission, paras.  75, 76, and 307.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  requirements; and (iv)  the 2016  Tuna Measure as a whole. In its Notice of Appeal, Mexico does not 
separately challenge  the Panels' findings regarding the determination provisions.561 
6.151.   We begin with a few preliminary observations. First, we recall that the Appellate  Body 
critici zed the first compliance panel's analysis because, while the first compliance panel had initially 
emphasized the interlinkages between elements of the 2013  Tuna Measure:  
[I]t 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 [2013 Tuna Measure].562 
6.152.   In the first compliance proceedings, the Appellate  Body re cognized that it may be 
appropriate for a panel "to proceed by assessing different elements of [a] measure in a sequential 
manner", provided that doing so does not "lead to the isolated consideration of a particular element" 
where the elements of a measure  are closely interrelated.563 Similarly, an assessment of the 
even-handedness of the 2016  Tuna Measure "must take account of the  fact that its various 
elements  – the eligibility criteria, the certification requirements, and the tracking and verification 
requirements – establish a series of conditions of access to the dolphin -safe label that are cumulative 
and highly interrelated".564  
6.153.   In these compliance proceedings, as described in  paragraph 6.149 above, the Panels first 
examined the different elements of the 2016 Tuna Measure (i.e. the eligibility criteria, the 
certification requirements, the tracking and verification requirements, and the determination 
provisions) in a sequential manner before synthesizing their analysis in order to reach their 
conclusion as to the consistency of the 2016 Tuna Measure with the WTO  Agreement.565 As indicated 
above, analysing the measure in a sequential manner does not, in itself, render the analysis 
erroneous. Rather, in reviewing the Panels' analysis, we examine whether it resul ted in an "isolated 
consideration of a particular element"566, or whether the Panels' analysis took into account the 
manner in which the discrete elements of the 2016 Tuna Measure are "cumulative and highly 
interrelated".567 
6.154.   Second, we take note that, in chall enging the Panels' assessment of the component elements 
of the 2016 Tuna Measure, Mexico contends, in several places, that the Panels' erroneous evaluation 
of the relevant risk profiles resulted in an error in the Panels' assessment of the 2016 Tuna 
Measur e.568 In sections  6.1.3.2  and 6.1.4 above, we addressed Mexico's claim that the Panels erred 
in their evaluation of the risk profiles. Thus, to the extent that Mexico's arguments in support of its 
claim that the Panels erred in their assessment of the compon ent elements of the 2016 Tuna Measure 
mirror Mexico's arguments  that we addressed and rejected  above , we refer to our analysis in those 
sections and do not revisit Mexico's arguments. Instead, we focus our review of the Panels' analysis 
on Mexico's argumen ts that are not premised on the alleged errors in the Panels' evaluation of the 
risk profiles.  
6.155.   We now turn to Mexico's challenges to the Panel's assessment of the following aspects of 
the 2016  Tuna Measure: (i)  the eligibility criteria; (ii)  the certificat ion requirements; (iii)  the 
tracking and verification requirements; and (iv)  the 2016  Tuna Measure as a whole.  
                                                
561 These findings are contained in paragraphs  7.677 -7.702 of the Panel Reports.  
562 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.21. We note that the 
Panels in these compliance proceedings took account of this reasoning by the Appellate  Body in setting out 
their approach to their assessment of the 2016 Tuna Measure. (Panel Reports, paras.  7.527 -7.530)  
563 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.14-7.15. 
564 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.166.  
565 Panel Reports, para.  7.530 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico ), para.  7.21). See also ibid., paras.  7.703 -7.716.  
566 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.15. 
567 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.166.  
568 See e.g. Mexico's appellant's sub mission, paras.  233-237, 241 -246, 252, 267, 273 -274, and 306.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.1.5.2   Eligibility criteria  
6.156.   Mexico claims that the Panels erred in finding that the eligibility criteria embodied in the 
2016 Tuna Measure are calibrate d to the risks to dolphins arising from the use of different fishing 
methods in different areas of the ocean.569 Mexico contends that the Panels undertook an incomplete 
calibration assessment that failed to assess the eligibility of all fishing methods and o cean areas, by 
failing to assess and take into consideration the risk profiles of different ocean areas, and by omitting 
relevant and important factors from the calibration assessment.570 
6.157.   The United  States asserts that all of Mexico's arguments are without m erit and should be 
rejected. In this regard, the United  States argues that: (i)  Mexico's a ttempt to undermine the 
Panels'  factual findings concerning the nature and content of the eligibility criteria is inappropriate 
and incorrect; (ii)  the Panels' analys is of the eligibility criteria encompassed both the ineligibility of 
setting on dolphins and the potential eligibility of the other relevant fishing methods; (iii)  the Panels 
did not fail to conduct the necessary analysis of the risk profiles of the releva nt fishing methods, 
including as used in different ocean areas; and (iv)  the Panels' analysis did not omit critical factors.571 
6.158.   Under t he 2016 Tuna Measure , the following tuna products are automatically ineligible for 
the dolphin -safe label: (i)  tuna harvest ed using large -scale driftnets on the high seas; and (ii)  tuna 
harvested by vessels using purse seine nets to encircle (i.e. set on) dolphins anywhere in the 
world.572 All other tuna products are eligible and may be labelled dolphin -safe only if  no dolphins 
were killed or seriously injured in the gear deployments in which the tuna was caught.  To this end, 
these tuna products must satisfy the certification and tracking and verification requirements of the 
2016 Tuna Measure.573 
6.159.   As part of the 2016 Tuna Measure, the relevant regulatory distinction under the eligibility 
criteria is that tuna  products containing tuna  caught by setting on dolphins are ineligible  for the 
dolphin -safe label, while tuna products containing tuna caught b y other fishing methods  are, in 
principle, eligible for the label.574 Thus, to assess whether this distinction is properly calibrated, the 
Panels were required to compare the risk profiles of relevant fishing methods. As discussed in 
paragraph s 6.94-6.95 above, in  assessing and comparing the over all relative risks of the 
seven  different fishing methods575, the Panels took account of relevant information pertaining to the 
risks to dolphins in individual fisheries, to the extent that evidence with respect to  such individual 
fisheries was presented to the Panels.576 In particular, the Panels found that setting on dolphins 
poses a much higher risk of observed dolphin mortality and serious injury, on a per  set basis, than 
other fishing methods.577 Moreover, in terms of t he magnitude of observed harms, the Panels found 
that the greater risks caused by setting on dolphins appeared to justify the finding of the original 
and first compliance panels that setting on dolphins is "particularly harmful" to dolphins.578 The 
Panels al so determined that the method of setting on dolphins is more likely than other fishing 
methods to cause unobserved mortality and serious injury.579 In addition, the Panels accepted, based 
on their assessment of the evidence on the record, that setting on dol phins causes a unique kind of 
unobservable harm that by its nature cannot be certified. The Panels noted that this contrasted with 
                                                
569 Mexico's Notice of Appeal, para.  9.a (referring to Panel Reports, paras.  7.539 -7.547).  
570 Mexico's appellant's submission, para.  247 (referring to Panel Reports, paras.  7.538 -7.547).  
571 United  States' appellee's submission, para.  206. 
572 Panel Reports, para.  7.50 (referring to DPCIA (Panel Exhibits MEX -1 and USA -1), Section  1385(d); 
2016 implementing regulations (Panel Exhibits MEX -2 and USA -2), Section  216.91(a)). See also ibid., 
para. 7.532.  
573 Panel Reports, para.  7.50. 
574 As noted in paragraph 6.158 above, the measure also automatically disqualifies tuna caught using 
large-scale driftnets on the high seas from the dolphin -safe label. Before the Panels, the parties did not submit 
"arguments concer ning the disqualification of tuna caught by driftnet on the high seas". (Panel Reports, fn  936 
to para.  7.532) For the reasons stated in paragraphs 6.69 -6.70 above, this regulatory distinction is not 
relevant for assessing whether the detrimental impact fo und in this dispute stems exclusively from a legitimate 
regulatory distinction.  
575 We recall that the seven fishing methods that the Panels discussed are: purse seine fishing by setting 
on dolphins; purse seine fishing without setting on dolphins; gillnet f ishing; longline fishing; trawl fishing; tuna 
handlining; and pole and line fishing. (See para. 6.86 above)  
576 See e.g. Panel Reports, para.  7.541.  
577 Panel Reports, para.  7.541.  
578 Panel Reports, para.  7.542 (quoting First Compliance Panel Report, para.  7.120).  
579 Panel Reports, para.  7.543.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  other fishing methods, which, based on the evidence before the Panels, do not cause the same kinds 
of unobservable harms as s etting on dolphins.580 
6.160.   For these reasons, the Panels concluded that "overall, the risk profile of setting on dolphins 
is much higher than that of each of the other six fishing methods used to catch tuna."581 The Panels 
relied on this conclusion582 in finding tha t, "[t]aking into account the relative risk profiles of setting 
on dolphins, on the one hand, and other fishing methods on the other hand, … the eligibility criteria 
are appropriately calibrated to the risks to dolphins arising from the use of different fi shing methods 
in different areas of the ocean."583  
6.161.   Mexico's arguments584 in support of its claim that the Panels erred in their assessment of 
the eligibility criteria of the 2016 Tuna Measure largely repeat Mexico's arguments that we addressed 
and rejected in our review of the Panels' evaluation of the relevant risk profiles. In particular, we 
recall that, under Article  2.1 of the TBT  Agreement, the relevant question is whether the detrimental 
impact caused by the 2016 Tuna Measure stems exclusively from a legitimate regulatory distinction. 
As described above, the detrimental i mpact in this dispute results, in part, from the distinction under 
the eligibility criteria between setting on dolphins and other fishing methods. Consequently, the test 
of whether the eligibility criteria are even -handed requires an assessment of whether the distinction 
between setting on dolphins and other fishing methods in the eligibility criteria is explained by the 
differences in the risk profiles of the fishing methods.  
6.162.   As we found above, for the purpose of this assessment, the Panels adopted the cor rect 
approach by comparing the risk profiles of the different fishing methods, on the basis of their 
examination of the evidence concerning the use of these fishing methods in different ocean areas.585 
Moreover, following our review of the Panels' evaluation  of the relevant risk profiles, we found that 
Mexico has not demonstrated that the Panels erred by drawing conclusions on the risk profile of each 
fishing method on the basis of their examination of the evidence before them (including evidence 
pertaining t o individual fisheries).586 Having found no legal error in the Panels' assessment of risk 
profiles, we see no reason to vacate the Panels' conclusion, following that assessment, that "setting 
on dolphins is significantly more dangerous to dolphins than are o ther fishing methods ."587 
6.163.   We now turn to Mexico 's arguments that concern whether the eligibility criteria under the 
measure are properly calibrated. Mexico points to evidence that it submitted to the Panels concerning 
the dangers of other fishing methods, ar guing that this evidence demonstrates that, for these fishing 
methods and ocean areas, there are regular and substantial dolphin mortalities and serious injury. 
Mexico asserts that the failure of the eligibility criteria to " designate such tuna as ineligib le" 
demonstrates that the tuna measure is not calibrated to differences in the risk profiles of different 
fishing methods in different ocean areas.588 
6.164.   These arguments by Mexico fail to take account of how t he various elements of the 
2016 Tuna Measure work to gether. As the Appellate  Body explained in the first compliance 
proceedings, the eligibility criteria are the "substantive conditions for access to [a] dolphin -safe 
label".589 However, the eligibility criteria are not the only conditions for access to a dolp hin-safe 
label. The certification requirements and the tracking and verification requirements "work together" 
with the eligibility criteria of the 2016  Tuna Measure "to limit access to the dolphin -safe label".590 
This means that, with respect to the category  of tuna products that are not automatically disqualified 
by the eligibility criteria, these products must still satisfy the certification requirements and the 
tracking and verification requirements before they can access the dolphin -safe label. For exampl e, 
                                                
580 Panel Reports, paras.  7.544 -7.546.  
581 Panel Reports, para.  7.525.  
582 Panel Reports, para.  7.539.  
583 Panel Reports, para.  7.540.  
584 Mexico's appell ant's submission, paras.  230-247. 
585 See para. 6.77 above.  
586 See para. 6.99 above.  
587 Panel Reports, para.  7.539.  
588 Mexico's  appellant's submission, paras.  238-240. (emphasis added)  
589 Panel Reports, para.  7.532 (quoting Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.19).  
590 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.159.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the certification requirements, which the Panels addressed in a later section of their Reports591, 
provide that tuna intended to be labelled as dolphin -safe in the US  market must be accompanied 
by, inter alia, a certificate attesting that: (i)  no dolphins  were killed or seriously injured during the 
sets in which the tuna was caught; and (ii)  no purse seine net or other fishing gear was intentionally 
deployed on or used to set on dolphins during the fishing trip in which the tuna was caught.592 Thus, 
contrary  to Mexico's arguments, under the 2016  Tuna Measure, tuna caught with fishing methods 
that, while provisionally eligible under the eligibility criteria, cause adverse effects to dolphins would 
not have access to the dolphin -safe label if they do not fulfil  the other labelling conditions under the 
2016 Tuna Measure (i.e.  the certification requirements and the tracking and verification 
requirements).  
6.165.   Mexico also contends that the Panels erred by omitting from their assessment factors related 
to the circumstan ces affecting the regulatory reliability of different ocean areas. According to Mexico, 
"[d]olphins are at a greater overall risk in ocean areas with insufficient regulatory oversight, 
unreliable reporting, IUU fishing and trans -shipment at sea than in oce an areas that do not have 
these attributes."593 Thus, Mexico stresses that tuna caught in such ocean areas by any fishing 
method that causes adverse effects to dolphins " should be ineligible for the label  and therefore 
discouraged".594 
6.166.   However, as discussed i n section 6.1.3.1.2 above, we  share the Panels' view that the risks 
of inaccurate certification, reporting, and/or record -keeping are not:  
[R]isks that arise from the use of different fishing methods in different areas of the 
ocean, even though fish caught  in different areas of the ocean through the use of 
different fishing methods may be associated with a greater or smaller risk of inaccurate 
labelling depending on a range of interconnected factors, including the persons involved 
in the catch, available te chnology, and applicable domestic and international regulatory 
requirements.595 
6.167.   Accordingly, we f ind that the Panels did not err in stating that "the risks of inaccurate 
certification, reporting, and/or record -keeping are not risks that affect dolphins thems elves" .596 In 
any event, in response to questioning at the hearing, Mexico conceded that there was no evidence 
on the record substantiating its assertion that "[d]olphins are at a greater overall risk in ocean areas 
with insufficient regulatory oversight, un reliable r eporting, IUU fishing and trans shipment at sea 
than in ocean areas that do not have these attributes."597 
6.168.   We have found that the Panels did not err in finding that "setting on dolphins is significantly 
more dangerous to dolphins than are other fish ing methods ."598 This finding implies that the 
                                                
591 Panel Reports, section  7.8.3. We review the Panels' findings concerning the certification requirements 
under the 2016 Tuna  Measure in section 6.1.5.3 below.  
592 Panel Reports, para.  7.549.  
593 Mexico's appellant's submission, para.  246. In response to questioning at the hearing, Mexico 
indicated that there was evidence on the Panel record illustrating the existence of risks arisi ng from insufficient 
regulatory oversight, IUU fishing, and trans -shipment at sea. However, Mexico conceded that there was no 
evidence on the record to demonstrate that  dolphins are at a greater overall risk in ocean areas where these 
attributes exist than  in ocean areas where the method of setting on dolphins is practised. Instead, Mexico 
clarified that the assertion, in its appellant's submission, about "dolphins [being] at a greater overall risk in 
ocean areas  with insufficient regulatory oversight, unre liable reporting, IUU fishing and trans -shipment at sea" 
was made merely as "a point of argument" in support of its view that the Panels should have turned their 
attention to all of the factors that are relevant to the general objective of discouraging fis hing practices that 
harm dolphins.  
594 Mexico's appellant's submission, para.  246. (emphasis added)  
595 Panel Reports, para.  7.110 (referring to First Compliance Panel Report, paras.  7.169 and  7.372, and 
fn 464 to para. 7.258, fn 681 to para. 7.463, and fn 711  to para. 7.502).  
596 Panel Reports, para.  7.110. (emphasis added)  
597 Mexico's appellant's submission, para.  246. As discussed in section 6.1.3.1 above, factors that affect 
the ultimate accuracy of the dolphin -safe label are relevant to assessing whether the labelling conditions under 
the measure are properly calibrated. In this vein, we recall that the certification requirements and the tracking 
and verification requirements, which, inter alia, address such factors, "work together" with the eligibility 
criter ia of the 2016  Tuna Measure "to limit access to the dolphin -safe label". (Appellate  Body Report,  
US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.159)  We review the Panels' examination of the 
certification requirements and the tracking and verificat ion requirements in sections 6.1.5.3 and 6.1.5.4 below.  
598 Panel Reports, para.  7.539. See also ibid., para. 7.525.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  distinction in the eligibility criteria between setting on dolphins, on the one hand, and other fishing 
methods, on the other hand, is, as the Panels found, "appropriately calibrated to the risks to dolphins 
arising from the use of different fishing methods in different areas of the ocean".599 Accordingly, we 
find that Mexico has not demonstrated that the Panels erred in reaching the intermediate finding 
that the eligibility criteria embodied in the 2016  Tuna Measu re are calibrated to the risks to dolphins 
arising from the use of different fishing methods in different areas of the ocean.600 
6.1.5.3   Certification requirements  
6.169.   Mexico asserts that the Panels erred in finding that the different certification requirements 
are cali brated to the risks to dolphins arising from the use of different fishing methods in different 
areas of the ocean.601 In addition to its arguments challenging the Panels' assessment of the risk 
profiles602, Mexico also contends that the Panels erred: (i)  by not addressing the fact that the 
2016 Tuna Measure requires observer certifications in seven US domestic fisheries when the 
observers are on  board for other reasons603; (ii) by finding that the measure can be considered 
calibrated where it allows higher margins of error for certifications in all ocean areas other than the 
ETP; and (iii)  by finding that the determination provisions contribute to the calibration of the 
measure, even though the determination provisions are only potentially applicable to a fi shery that 
has a much higher risk profile than the one found by the Panels for the ETP large purse seine 
fishery.604 
6.170.   The United  States maintains that: (i)  Mexico is wrong to argue that the Panels erred in not 
addressing the observer certification requirement s on the seven US domestic fisheries605; (ii) the 
Panels' analysis and conclusions concerning margins of error did not constitute legal error606; and 
(iii) the Panels did not err in their analysis and conclusions concerning the determination 
provisions.607 
6.171.   As de scribed in section  5 above , with respect to the certification requirements, apart from 
large-scale driftnet fishing on the high seas608, the 2016 Tuna Measure makes a distinction between 
the ETP large purse seine fishery, on the one hand, and all other fishe ries, on the other hand.609 For 
tuna caught in the ETP large purse seine fishery, the 2016 Tuna Measure mandates that certification 
must be provided by the captain of the vessel and an IDCP -approved observer that: (i)  none of the 
tuna was caught on a trip us ing a purse seine net intentionally deployed on or used to  encircle 
dolphins; and (ii)  no dolphins were killed or seriously injured during the sets in which the tuna was 
caught.610 
6.172.   As for all fisheries other than the ETP large purse seine fishery, for fishin g trips that began 
on or after 21  May 2016, captains  of all vessels must certify that: (i)  no purse seine net or other 
fishing gear was intentionally deployed o n or used to encircle (i.e.  set on) dolphins during the fishing 
trip in which the tuna was caugh t; and (ii)  no dolphins were killed or  seriously injured in the sets or 
other gear deployments  in which the tuna was caught.611 Additionally, under the 2016 Tuna Measure, 
                                                
599 Panel Reports, para.  7.540.  
600 Panel Reports, para.  7.547. See also ibid., para.  7.540.  
601 Mexico's Notice of Appeal, para.  9.b (referring to  Panel Reports, paras.  7.571 -7.573 
and 7.600 -7.611).  
602 Mexico's appellant's submission, para.  252. See also para. 6.154 above.  
603 Mexico's appellant's submission, para.  258 (referring to First Compliance Report, para.  3.46; 
United  States' first written subm ission to the Panels, fn  225 to para.  116).  
604 Mexico's appellant's submission, para.  267. 
605 United  States' appellee's submission, para.  264. 
606 United  States' appellee's submission, para.  244. 
607 United  States' appellee's submission, para.  244. 
608 Panel Reports, para.  7.51 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(3)).  
609 Panel Reports, paras.  7.51 and 7.54 (referring to 2016  implementing regulations (Panel Exhibits 
MEX-2 and USA -2), Section  216.91(a)(1) and (3)).  
610 Panel Reports, para.  7.54 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(1)). See also 2016  implementing regulations (Panel Exhibits MEX -2 and USA -2), 
Section  216.92.  
611 Panel Reports, pa ra. 7.51 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(3)(iii)).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the captains of the vessels in all fisheries other than  the ETP large purse seine fishe ry must certify 
that they have completed the Captain Training Course.612 
6.173.   Moreover, in addition to the captain's certification described above, in certain circumstances, 
certifications from an observer participating in a national or international programme ac ceptable to 
the Assistant Administrator will also be required. First, certification by the observer is also required 
in the seven US domestic fisheries for which the Assistant Administrator has determined that 
observers are qualified and authorized to make  the relevant certifications613, and when such an 
observer is already on board the fishing vessel for reasons unrelated to the dolphin -safe labelling 
regime.614 
6.174.   Furthermore, pursuant to the 2016 Tuna Measure, tuna caught in all fisheries other  than the 
ETP lar ge purse seine fishery  may, under specified circumstances, require an observer615 certification 
in addition to the captain certification. This is the case where the Assistant Administrator has 
determined that in a fishery other than the ETP large purse seine  fishery: (i)  there is a regular and 
significant association between dolphins and tuna (similar to the association between dolphins and 
tuna in the ETP); or (ii)  a regular and significant mortality or serious injury of dolphins is occurring. 
The captain an d observer must certify that: (i)  no purse seine net or other fishing gear was 
intentionally deployed on or used to encircle (i.e. set on) dolphins during the trip on which the tuna 
was caught; and (ii)  no dolphins were killed or seriously injured in the s ets or other gear deployments 
in which the tuna was caught.616 
6.175.   In their analysis of the certification requirements, the Panels noted that, unlike the eligibility 
requirements, the certification requirements (and the tracking and verification requirements) dr aw 
distinctions based on both fishin g methods and ocean areas (i.e.  fisheries), rather than  solely on  
different fishing methods. Specifically, the distinctions are made between the ETP large purse seine 
fisheries and all other fisheries. Thus, the certific ation requirements that apply in the ETP large purse 
seine fishery apply to all large purse seine vessels fishing in the ETP, regardless of whether those 
vessels actually set on dolphins. Therefore, the Panels considered the question before them to be 
whether the distinction that the 2016  Tuna Measure makes between the ETP large purse seine 
fishery and all other fisheries is calibrated.617 
6.176.   In this regard, the Panels considered that the finding, from the original and first compliance 
proceedings, that setting on dolphins is practised routinely and systematically only in the ETP 
continued to be relevant to these compliance proceedings.618 The Panels also found relevant the 
finding of the original panel that "the association between schools of tunas and dolphins does not 
occur outside the ETP as frequently  as it does within the ETP ."619 In addition, the Panels recalled 
their conclusion that s etting on dolphins is a particularly dangerous fishing method that is liable to 
                                                
612 Panel Reports, para.  7.53 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(3)(iii)(B)).  
613 In the first compliance panel proceedings, the United  States identified the seven domestic fisheries 
where tuna is regularly harvested as: (i)  American Samoa Pelagic Longline Fishery; (ii)  Atlantic Bluefin Tuna 
Purse Seine Fishery; (iii)  Atlantic Highly Migr atory Species Pelagic Longline Fishery; (iv)  California Deep -set 
Pelagic Longline Fishery; (v)  California Large -mesh Drift Gillnet Fishery; (vi)  Hawaii Deep -set Longline Fishery; 
and (vii)  Hawaii Shallow -set Longline Fishery. (United  States' second written  submission to the first compliance 
panel, para.  128 and fn  244 thereto (referring to Determination of Observer Programs as Qualified and 
Authorized by the Assistant Administrator for Fisheries, United States Federal Register , Vol. 79, No. 134 
(14 July 201 4) (First Compliance Panel Exhibit US -113), p. 40720))  
614 Thus, in these fisheries, tuna caught on a trip where no observer is already on board may still be 
labelled dolphin -safe with only a captain's certification. (See First Compliance Panel Report, para.  3.46; 
Appellate Body Report, US – Tuna II (Mexico) (Article 21.5 – Mexico) , para. 6.23 and fn  171 thereto)  
615 This observer is described as one "participating in a national or international program acceptable to 
the Assistant Administrator". (2016  implemen ting regulations (Panel Exhibits MEX -2 and USA -2), 
Section  216.91(a)(3)(v). See also Panel Reports, para. 7.68)  
616 Panel Reports, para.  7.68 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(3)(v)).  
617 Panel Repo rts, para.  7.568.  
618 Panel Reports, para.  7.570.  
619 Panel Reports, para.  7.569 (quoting Original Panel Report, para.  7.520 (fn omitted; emphasis 
original)). We also take note of the Panels' observation, in the context of their assessment of the risk profiles , 
that "due to the significant and regular association between tuna and dolphins in the ETP, even purse seine 
fishing without setting on dolphins might end up, inadvertently, interacting with dolphins, perhaps even at a 
higher rate than purse seine fishing  by setting on dolphins or other fishing methods in other areas of the 
ocean." (Ibid., para.  7.333)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  cause observable and unobservable harms to dolphins at rates significantly in excess of those caused 
by other fishing methods.620 The Panels observed that, in the ETP, unlike in other areas of the ocean, 
large purse seine vessels are permitted  to and actually can  set on dolphins in a consistent and 
systematic manner. The Panels highlighted that one of the purposes of the certification requirements 
in the ETP is precisely to certif y that dolphins were not set on, even though the fishing vessels could, 
both technically and legally, have set on dolphins. Thus, in the Panels' view, it is both the technical 
and legal possibilit ies of setting on dolphins and the fact that dolphin sets oc cur in a consistent and 
systematic manner in the ETP large purse seine fishery that give this fishery its special risk profile.621 
6.177.   On appeal, Mexico challenges the Panels' finding that the ETP large purse seine fishery has 
a "special risk profile", arguing t hat the Panels failed to compare individual fisheries.622 We first note 
that Mexico's arguments concerning the Panels' alleged failure to assess individual fisheries repeat 
Mexico's arguments addressed in section  6.1.4 above.623 In particular , we recall that, in assessing 
whether there is "treatment no less favourable" under Article  2.1 of the TBT  Agreement for the 
purpose of this dispute, the analysis should "focus[] on the regulatory distinction(s) causing the 
detrimental impact on imported products".624 With r espect to the certification requirements, the 
2016 Tuna Measure makes a distinction between the ETP large purse seine fishery and all other 
fisheries.625 We also recall our finding that, with respect to the certification requirements (and the 
tracking and ve rification requirements), the Panels adopted the correct approach in comparing the 
risk profiles of individual fisheries, because these requirements make a distinction on the basis of 
both fishing method and ocean area.626 Moreover, as discussed in  section 6 .1.4 above, the Panels 
examined all available evidence before them regarding the risks to dolphins in individual fisheries, 
and Mexico has not substantiated its claim that the Panels erred in assessing such risks. On the basis 
of their assessment of risks to dolphins in individual fisheries, the Panels established that "in the 
ETP, unlike in other areas of the ocean, large purse seine vessels are permitted  to and actually can  
set on dolphins in a consistent and systematic manner."627 Thus, we understand that, having 
assessed the risk profiles of individual fisheries, the Panels established that, when compared to the 
ETP large purse seine fishery, which has a "special risk profile", all the other fisheries are similar in 
their risk pro files insofar as in none of them is setting on dolphins practised consistently or 
systematically.  
6.178.   In this regard, we take note of Mexico's allegation that the Panels did not address the fact 
that only certain  large purse seine vessels in the ETP, i.e. thos e that have been assigned an individual 
DML, "are permitted to and actually can set on dolphins in a consistent and systematic manner".628 
As a preliminary matter, we observe that Mexico's argument that vessels either set on dolphins or 
do not, and that the ETP fishery can be divided into vessels with and without DMLs, was not made 
before the Panels and finds no sup port o n the Panel record.629 
6.179.   More importantly, in their evaluation of the certification requirements, the Panels expressly 
addressed the issue of wh y the ETP large purse seine fisheries have a special risk profile, regardless 
of whether setting on dolphins is actually practised. In particular, the Panels noted that:  
[T]he crucial point is that in the ETP, unlike in other areas of the ocean, large purs e 
seine vessels are permitted  to and actually can  set on dolphins in a consistent and 
                                                
620 Panel Reports, para.  7.571.  
621 Panel Reports, para.  7.572.  
622 Mexico's appellant's submission, para.  255 (quoting Panel Reports, para. 7.572).  
623 Mexico's ap pellant's submission, para.  252. 
624 Appellate  Body Reports, US – COOL (Article  21.5 – Canada and Mexico) , para.  5.93. See also 
Appellate  Body Report, US – Tuna II (Mexico) , para.  286. 
625 See para. 6.65 above. See also Panel Reports, paras. 7.51 -7.54; 2016  implementing regulations 
(Panel Exhibits MEX -2 and USA -2), Section  216.91(a)(1) and (3).  
626 See para. 6.77 above.  
627 Panel Reports, para.  7.572. (emphasis original)  
628 Mexico's appellant's submission, para.  256. 
629 To the contrary, the United  States, in its appe llee's submission, points us to evidence on the Panel 
record that indicates that vessels with DMLs may not set on dolphins during particular trips either because they 
choose not to or because they have reached their DML for the year. Further, DMLs can be t ransferred or 
changed mid -year, so the fact that a vessel was not given a DML does not mean that it can never legally set on 
dolphins that year. (United  States' appellee's submission, para.  262 (referring to AIDCP, Report on the 
International Dolphin Conse rvation Program , Doc.  MOP-28-05, 18  October 2013 (Panel Exhibit MEX -8), 
pp. 2-3; AIDCP, Report on the International Dolphin Conservation Program , Doc.  MOP-32-05, 20  October 2015 
(Panel Exhibit USA -15), pp.  2-3)) WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  systematic manner. … Thus, it is not simply the fact that dolphins are set on in the ETP 
large purse seine fishery that gives it its "special risk profile", but the fact that only in 
the ETP are large purse vessels actually able and permitted to set on dolphins. Thus, in 
our view, it is both the technical and legal possibility of setting on dolphins and the fact 
that dolphin sets occur in a consistent and systematic manner  in the ETP large purse 
seine fishery that gives this fishery its special risk profile.630 
6.180.   Beyond its argument concerning DMLs, which we have addressed above, Mexico does not 
offer additional reasons why the above -quoted statements from the Panels are errone ous. Moreover, 
as we found in section  6.1.4.2  above , Mexico has not demonstrated that the Panels failed to assess 
the risk profiles of individual fisheries.631 Having found no legal error in the Panels' assessment of 
risk profiles, we see no reason to void t he Panels' finding that "it is both the technical and legal 
possibility of setting on dolphins and the fact that dolphin sets occur in a consistent and systematic 
manner in the ETP large purse seine fishery that gives this fishery its special risk profile. "632 
6.181.   Mexico also alleges that the Panels failed to address the fact that the 2016  Tuna Measure 
requires observer certifications in seven US  domestic fisheries when the observers are on board for 
other reasons.633 For Mexico, this raises questions such as wheth er those seven fisheries are "high 
risk", or whether the enhanced certification requirements are imposed for reasons other than those 
identified by the Panels.634 The United  States points out that, before the Panels, Mexico never put 
forward any argument tha t the additional observer requirement i mposed on some US vessels in 
US fisheries renders the 2016 Tuna M easure not even -handed. The United  States adds that Mexico 
has not suggested a reason for claiming that the Panels' failure to refer to this observer ce rtification 
requirement renders their analysis "legally in error".635 In response to questioning at the hearing, 
Mexico clarified that its argument was not that the observer certification requirement, in and of 
itself, renders the measure not even -handed. Ra ther, Mexico was referring to the Panels' failure, in 
their analysis, to address this requirement as yet another illustration of the incoherence of the 
Panels' calibration analysis and of their failure to take account of all relevant factors.  
6.182.   We observe that Mexico's argument concerns an aspect of the certification requirements on 
which the Panels made no finding . Before the Panels in these compliance proceedings, Mexico 
referred to the observer certifications reflected in the first compliance panel report in describing the 
certification requirements under the 2016 Tuna Measure.636 However, Mexico did not raise specific 
concerns regarding these observer certifications, either during the first compliance proceedings or 
before the Panels in these co mpliance proceedings . 
6.183.   We recall that, in the first compliance proceedings, the United States identified seven 
domestic fisheries where tuna is regularly harvested.637 These seven US fisheries have a certain 
level of observer coverage, meaning that observers may be on board the fishing vessels in these 
fisheries for reasons unrelated to the dolphin -safe labelling regime.638 As noted by the first 
compliance panel and th e Appellate Body, the Assistant  Administrator has determined that, in 
addition to the captain's  certification, the observers in these fisheries are qualified and authorized 
                                                
630 Panel Reports, para.  7.572. (emphasis orig inal; fns  omitted)  
631 See para. 6.99 above.  
632 Panel Reports, para.  7.572.  
633 See para. 6.173 and fn 613 above.  
634 Mexico's appellant's submission, para.  258 (referring to First Compliance Panel Report, para.  3.46; 
United  States' first written submission to th e Panels, fn  225 to para.  116, in turn referring to 2016 
implementing regulations (Panel Exhibits MEX -2 and USA -2), Section  216.91(a)(3)(iv); First Compliance Panel 
Report, para.  3.45).  
635 United  States' appellee's submission, para.  264. 
636 Mexico's first written submission to the Panels, para.  128 (referring to First Compliance Panel Report, 
para. 3.46).  
637 See supra , fn 613.  
638 United States' second written submission to the first compliance panel, para. 128 and fn  245 thereto 
(referring to NMFS, National Observer Program FY 2012 Annual Report  (2013) (First Compliance Panel Exhibit 
US-114), pp. 29 -38). WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  to make the certifications required for the dolphin -safe label.639 Thus, with respect to these 
seven  US fisheries, the 2016 Tuna Measure, similar to the 2013 Tuna Measure, conditio ns access to 
the dolphin -safe label on the provision of both captain and observer certifications, but only when an 
observer is already on board the vessel. It is unclear to us why the presence of observers on board 
fishing vessels in the seven US fisheries , for reasons unrelated to the dolphin -safe labelling regime, 
"raises questions such as whether those seven fisheries are 'high -risk'".640 
6.184.   In any event , regardless of the reasons for which such an observer may already be on board 
the vessel under the 2016 Tu na Measure,  we note that  the observer is required to prepare a written 
statement certifying that: (i)  no dolphins were killed or seriously injured in the sets or other gear 
deployments in which the tuna was caught; and (ii)  in purse seine fisheries, no pur se seine net was 
intentionally deployed on or used to encircle dolphins during the trip on which the tuna was caught.641 
We recall that the aim of the Panels' calibration analysis was to establish whether "the distinctions 
drawn between different tuna fishin g 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."642 On its face, this requirement appears to reduce the differences in the requirements 
applicable to the ETP large purse seine fishery and those applicable to all other fisheries, by making 
use of an already available observer resource on board the vessel to complement the efforts of the 
captain of the vessel in meeting the certification requirem ents. In our view, therefore, Mexico has 
not demonstrated how this observer requirement renders the treatment accorded un der the 
2016 Tuna Measure to the different fisheries not even -handed.  
6.185.   We now turn to Mexico's contention that the Panels did not approa ch the calibration test 
from the perspective of accuracy, taking account of the objectives of the measure, but rather from 
the perspective of how much inaccuracy should be tolerated, notwithstanding the objectives. Mexico 
points to the Panels' statement th at "[w]e … do not believe that, by tolerating a higher or lower  
margin of error, the certification requirements conflict with the objectives of the 
2016 Tuna Measure ."643 Mexico contends that the Panels did not explain how tolerating error can be 
reconciled with, or rationally connected to, the consumer -information and dolphin -protection 
objectives of the measure. Mexico posits that, if the Panels had done so, they may hav e found that 
the detrimental impact caused by the 2016  Tuna Measure cannot be justified on the basis of 
regulatory distinctions that tolerate different margins of error.  
6.186.   The United  States argues that the Panels' statements concernin g margins of error in th ese 
compliance proceedings do not suggest that there are differences in label accuracy for tuna produced 
from the ETP large purse seine fishery and other fisheries. For the United  States, a more sensitive 
mechanism does not necessarily mean a more accurate  label. Rather, the risk profile of a fishery 
must also be taken into account.644 
6.187.   As described in section  6.1.3.1.3 above,  the Panels first introduced the term "margin of 
error" when examining, as a general matter, the relevance of the risk of inaccurate lab elling to their 
calibration analysis. As analysed in that section, the Panels used this term to refer to the sensitivity 
of the relevant labelling conditions. In that context, we find that the Panels correctly recognized that 
the accuracy of the ultimate l abel depends not only on the sensitivity of the labelling conditions, but 
                                                
639 First Compliance Panel Report, para. 3.46; Appellate  Body Report, US – Tuna II (Mexico) 
(Article  21.5 – Mexico) , fn 171 to para. 6.23. See also 2016 implementing regulations (Panel Exhibits MEX -2 
and USA -2), Section 216.91(a)(3)(iv). The United States pointed to evidence on the record of the first 
compliance panel indicating that the NMFS relies on fishery observers to collect data from US commercial 
fishing and processing vessels, as well as from some shore -side processing plants. In response to questioning 
at the hearing in these compliance proceedings, the United States indicated that the information collected by 
fisheries observe rs is used for a wide range of assessment and monitoring purposes, and supports the 
management and conservation of fisheries, protected resources, and ecosystems throughout the United States. 
(NMFS, National Observer Program FY 2012 Annual Report  (2013) (F irst Compliance Panel Exhibit US -114), 
pp. vi-vii and 1 -4) 
640 Mexico's appellant's submission, para. 258.  
641 2016 implementing regulations (Panel Exhibits MEX -2 and USA -2), Section  216.91(a)(3)(iv).  
642 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.108 (referring to 
Appellate  Body Report, US – Tuna II (Mexico) , paras.  282-284).  
643 Mexico's appellant's submission, para.  263 (quoting Panel Reports, para.  7.607).  
644 United  States' appellee's submission, para.  269 (referring to Panel R eports, paras.  7.599, 
7.603 -7.604, and 7.607).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  also on the level of risks to dolphins in a fishery. In our view, the Panels used the term "margin of 
error" in the same sense in their evaluation of the certification requirements.  
6.188.   Mexico takes issue with the Panels' statement that, "[i]n the context of the certification 
requirements , … it is calibrated for the United  States  to tolerate a higher margin of error in respect 
of fisheries other than the ETP large purse seine fishery and to tolerate a lower margin of error inside 
the ETP large purse seine fishery."645 The Panels' statement that Mexico refers to should be 
understood in its proper context. Specifically, the Panels were addressing Mexico's argument that 
the use of a less sensit ive mechanism outside the ETP large pur se seine fishery cannot be 
even-handed if it would result in the label becoming less accurate.646 In the Panels' view, Mexico's 
argument appeared to be premised on the notion that certification can guarantee accurate la belling 
in every case. However, the Panels considered the more pertinent question to be whether the 
possibility of error is commensurate with the different risks to dolphins arising from the use of 
different fishing methods in different areas of the ocean.  Accordingly, the Panels considered that "it 
is calibrated"647 for the United  States to require a more sensitive mechanism in the ETP large purse 
seine fishery, while "tolerating" a less sensitive mechanism in other fisheries, which have relatively 
lower ris k profiles. For the Panels, this distinction addresses the relative risks posed to dolphins in 
the ETP large purse seine fishery , on the one hand , and other fisheries , on the other hand , in a way 
that is calibrated to  the risk profiles of those fisheries.648 
6.189.   The Panels' statements above, read in their proper context, confirm our view that the Panels 
correctly focused on the question whether the sensitivity of the labelling conditions under the 
measure is calibrated to the level of risks to dolphins so as to e nsure the accuracy of the ultimate 
label. Indeed, as the Panels noted, the mere fact that a vessel has an observer on board does not 
necessarily, or by itself, mean that that vessel will produce a more accurate certification.649 Rather, 
accuracy is a functio n of potentially many variables, including not only the reporting requirements 
in place, but also the different levels of dolphin interaction, mortality, and serious injury in different 
fisheries.650 Thus, while an observer may strengthen the certification, such additional strength may 
not always be needed, for example, in fisheries where the risk profile is relatively low.651 
6.190.    Still with regard to the potential risk of inaccuracy of the dolphin -safe label, we take note 
of Mexico's assertion that the panel in t he first compliance proceedings found that "it may be easier  
or more likely  for dolphin -safe certifications made only by captai ns to be inaccurate", with 
"the consequence" that "it may be more likely that tuna caught by vessels other than large purse 
seine vessels in the ETP will be inaccu rately labelled as dolphin -safe."652 However, the first 
compliance panel did not make a definitive finding on this issue. Rather, the first compliance panel, 
in making the statements to which Mexico refers , also explained th at, although the United  States 
seemed to have made the "concession that observer certification heightens or increases the accuracy 
and reliability of the label", such a concession "does not entail the conclusion that, without observers, 
captains' certifica tions are always and necessarily 'inherently unreliable'".653 The first compliance 
panel added that, in its view, it was "not necessary to make a definitive finding on this point".654 
6.191.   In any event, the first compliance panel was addressing the 2013 Tuna Measure. The Panels 
in these compliance proceedings noted that, under the architecture of the 2016  Tuna Measure, the 
private tuna companies that supply the US  tuna market are subject to the requirements of the 
2016 Tuna Measure, and it is they that must ensure that the products they sell meet the conditions 
of US  law, "including that the captain certifications are accurate".655 The Panels considered that, 
unlike the situation under the 2013  Tuna Measure, the training course incorporated in the 
2016 Tuna Measure contains meaningful information concerning key aspects of the certification 
                                                
645 Panel Reports, para.  7.602.  
646 Panel Reports, para.  7.604 (referring to Mexico's response to Panel question No.  86, para.  147).  
647 Panel Reports, paras.  7.602 and 7.606.  
648 Panel Reports, para.  7.606 (referring  to Appellate  Body Reports, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.122; US – Tuna II (Mexico) , para.  292).  
649 Panel Reports, para.  7.608.  
650 Panel Reports, paras.  7.123 and 7.608.  
651 Panel Reports, para.  7.608.  
652 Mexico's appellant's submissi on, para.  263 (quoting First Compliance Panel Report, para.  7.168 
(emphasis original)).  
653 First Compliance Panel Report, para.  7.168. See also United  States' appellee's submission, para.  268. 
654 First Compliance Panel Report, para. 7.169.  
655 Panel Reports, p ara. 7.591.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  process that would assist captains to understand and properly carry out their responsibility to certify 
the dolphin -safe status of a set or other gear deployment. The Panels also considered that the 
training requirement is embedded within a sufficiently enforceable regulatory framework and is 
therefore not meaningless or unenforceable, as Mexico contended. In a ddition, the Panels took note 
that the Captain Training Course is now available online in nine  languages, including  the languages 
of all of the largest suppliers of tuna and tuna products, such as the Philippines, Chinese  Taipei, and 
Thailand, which Mexico  argues are significantly deficient in the control and monitoring of fishing 
activities.656 As the Panels explained, the training course was being actively disseminat ed by the 
United  States itself to facilitate the effective implementation of the training re quirement.657 In our 
view, the above findings illustrate the ways in which the Panels took account of the potential risks 
of inaccuracy when undertaking their calibration analysis.  
6.192.   Finally, we address Mexico's allegation that the Panels erred in finding that  the determination 
provisions "help to ensure that the 2016  Tuna Measure treats similar situations similarly " and "help 
to establish a mechanism for enforcing the eligibility criteria that are properly calibrated to the 
different risk profiles in different  fisheries ".658 Mexico argues that the Panels failed to take fully into 
account Mexico's assertion that the determination provisions do not allow calibration of the 
certification requirement to the extreme danger to dolphins in fisheries where stock sustaina bility is 
being threatened and a small number of dolphin mortalities can have disastrous consequences. For 
Mexico, the Panels' approach also ignored the high number of dolphin mortalities and serious injury 
when measured on an absolute basis.659 
6.193.   We recall th at, pursuant to the 2016 Tuna Measure, tuna caught in all fisheries other than  
the ETP large purse seine fishery  may require an observer660 certification in addition to the captain 
certification where the Assistant Administrator has determined that in a fish ery other than the 
ETP large purse seine fishery: (i)  there is a regular and significant association between dolphins and 
tuna (similar to the association between dolphins and tuna in the ETP); or (ii)  a regular and 
significant mortality or serious injury of dolphins is occurring. The captain and observer must certify 
that: (i)  no fishing gear was intentionally deployed on or used to encircle dolphins during the trip on 
which the tuna was caught; and (ii)  no dolphins were killed or seriously injured in the sets or other 
gear deployments in which the tuna was caught.661 
6.194.   We note that Mexico 's arguments concerning dolphin -stock sustainability and the 
Panel s' reliance on the per  set methodology (as opposed to absolute level s of mortalities  and serious 
injuries ) mirror its arguments relating to the Panels' evaluation of the risk profiles. These arguments 
have already been addressed and rejected in section  6.1.4.4  above .662 
6.195.   In addition, Mexico contends that the Panels failed to fully take into account the fact that , in 
applying the determination provisions, the Uni ted States relies on "a  20-year average of direct 
dolphin mortalities caused by dolphin sets in the ETP" between 1997 -2017 for determining whether 
there is a regular and significant mortality or serious in jury of dolphi ns in a particular fishery.663 
                                                
656 Panel Reports, paras.  7.594 and 7.675.  
657 Panel Reports, paras.  7.594 -7.595.  
658 Mexico's appellant's submission, para.  265 (quoting Panel Reports, para.  7.710).  
659 Mexico's appellant's submission, para.  266 (referring to Panel Reports, para.  7.683). 
660 An observer is described as one "participating in a national or international program acceptable to 
the Assistant Administrator". (2016  implementing regulations (Panel Exhibits MEX -2 and USA -2), 
Section  216.91(a)(3)(v). See also Panel Reports, para.  7.68)  
661 Panel Reports, para. 7.68 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.91(a)(3)(v)). We take note of the Panels' explanation that the determination provisions 
under the 2016 Tuna Measure have been appli ed on at least one occasion. On 28  September 2016, the 
Assistant Administrator issued a determination, based on the best information available, that a regular and 
significant mortality of dolphins was occurring in the Indian Ocean gillnet fisheries. The de termination provided 
that, for any tuna product produced from these fisheries to be marketed as dolphin -safe in the United  States, 
the product would have to be accompanied by a certification by an observer from a qualified and authorized 
observer program a nd a certification attesting to the catch documentation, the substance of the dolphin -safe 
labelling standards, and the chain of custody information. (See Panel Reports, paras.  7.685 -7.686)  
662 See also paras. 6.122 -6.143 above.  
663 Mexico's appellant's submis sion, para.  266 (referring to Panel Reports, para.  7.683). The 20 -year 
average encompasses a period that starts two years before the entry into force of the AIDCP regime when 
mortalities were higher. The 20 -year period also covers the years when there was dramatic reduction of 
observed dolphin mortality in the ETP, following the entry into force of the AIDCP regime. (See para. 5.2 
above; Original Panel Report, paras.  2.39 and 7.609)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Mexico con tends that, because the 20 -year average encompasses a period when dolphin mortalities 
were higher in the ETP, the US  benchmark under the determination provisions is materially higher 
than the  average mor talities between 2009 and 2015, on which the Panels relied "elsewhere".664 
According to Mexico, the Panels did not address this inconsistency in the data on which they relied. 
Mexico further contends that the Panels' finding suggests an approach under which,  if a fishery is 
found to have a lower per  set mortality rate t han the ETP (based on a 20 -year average), it is 
automatically  assumed that there are no , or de minimis , risks to dolphins. Mexico considers this to 
be "an erroneous application of the test for calibration".665 
6.196.   We recall that, in its Notice of Appeal, Mexico expressly challenges the Panels' evaluation of: 
(i) the eligibility criteria; (ii)  the certification requirements; (iii)  the tracking and verification 
requirements; and (iv) the 2016  Tuna Measu re as a whole.666 Mexico's Notice of Appeal does not 
include a claim challenging the Panels' discrete findings with respect to the determination 
provisions.667 Yet, in its appellant's submission, Mexico appears to challenge these very findings. 
Moreover, we no te that this allegation by Mexico does not directly concern the heightened 
certification requirements, which follow once the Assistant Administrator has made the 
determination: (i)  that a fishery other than the ETP  large purse seine fishery has either a re gular 
and significant association between dolphins and tuna (similar to the association between dolphins 
and tuna in the ETP); or (ii)  that a regular and significant mortality or serious injury of dolphins is 
occurring in a given fishery.668 Rather, Mexico's  allegation concerns the methodology adopted by the 
United  States to allow the Assistant Administrator to make such determinations, which the Panels 
did not address in their evaluation of the certification requirements, and which Mexico does not 
separately  challenge on appeal. Furthermore, in response to questioning at the hearing, Mexico 
explicitly stated that it was not challenging the Panels' discrete findings on the determination 
provisions. Instead, Mexico explained that its reference to the Panels' fi ndings was merely aimed at 
pointing out that the determination provisions do not remedy the lack of  even-handedness of the 
2016 Tuna Measure.  
6.197.   An assessment of the even -handedness of the 2016  Tuna Measure "must take account of 
the fact that its various elements … establish a series of conditions of access to the dolphin -safe 
label that are cumulative and highly interrelated".669 Thus, to the extent that Mexico's arguments 
concerning the US methodology for applying the determination provisions impact the 
even-handedness of the 2016 Tuna Measure, owing to the "cumulative and highly interrelated" 
aspects of the various conditions of access to the dolphin -safe label, we consider Mexico's arguments 
to be properly before us.  
6.198.   Mexico's arguments on appeal suggest t hat there is an inconsistency between the Panels' 
reliance on 2009 -2015 data from the  ETP in arriving at one finding  and the Panels' review of the 
data drawn from a 20 -year average covering 1997 and 2017 in their evaluation of the 
US methodology for applyi ng the determination provisions.670 Mexico's arguments appear to conflate 
two different aspects of the Panels' analyses. First, we recall that, in assessing whether the 
2016 Tuna Measure is consistent with Article  2.1 of the TBT  Agreement, the Panels first e xamined 
the risk profiles of the different fishing methods, as used in different areas of the ocean. In this 
regard, the Panels found that setting on dolphins caused both observable and unobservable harms 
to dolphins.671 Specifically, the Panels found that, "[w]ith regard to observable harms, … setting on 
dolphins in the ETP has caused on average 91.15  dolphin mortalities between 2009 and 2015."672 
For the purpose of  reviewing the eligibility criteria under the 2016 Tuna Measure, the Panels relied 
on, inter alia, this finding to conclude that "overall, the risk profile of setting on dolphins is much 
higher than that of each of the other six  fishing methods used to catch tuna ."673 
                                                
664 Mexico's appellant's submission, para.  266. 
665 Mexico's appellant's submission, para.  266. 
666 Mexico's Notice of Appeal, para.  9.a-d. 
667 Panel Reports, paras.  7.677 -7.702.  
668 Panel Reports, para.  7.677.  
669 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.166.  
670 Mexico's appellant's submission, para.  266. In challenging these findings of the Panels, we note that 
Mexico does not question the objectivity of the Panels' assessment of the facts, as required by Article  11 of the 
DSU. 
671 Panel Reports, para.  7.518.  
672 Panel Reports, para.  7.519.  
673 Panel Reports, para.  7.525.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.199.   Second, in assessing the determination provisions under the 2016  Tuna Measure, the Pa nels 
examined, inter alia, the methodology that the United  States uses under the determination 
provisions to assess the levels of mortality and serious injury to dolphins. In this regard, the Panels 
observed that the United  States uses an "average of per s et data" collected in the ETP between 1997 
and 2017 (which the United  States calculated as 0.1265 dolphin mortalities per set).674 Thus, in the 
context of the determination provisions, the Panels did not choose the data to rely on and were 
instead tasked wit h examining whether the methodology relied on by the United  States in applying 
their determination provisions was arbitrary, as had been alleged by Mexico.  
6.200.   Therefore, unlike what Mexico's arguments suggest, there is no inconsistency between the 
Panels' rel iance on 2009 -2015 data to examine the risk profiles of different fishing methods (based 
on the evidence on the record of their use in different areas of the ocean), on the one hand, and the 
Panels ' assessment of the US  methodology for applyi ng the determi nation provisions  based on data 
drawn from a 20 -year average covering 1997 -2017, on the other hand.675 
6.201.   Mexico also contends that the Panels' finding, in connection with the determination 
provisions, suggests an approach pursuant to which, if a fishery is dee med to have a lower per  set 
mortality rate than the ETP (based on a 20 -year average), and therefore not designated under the 
determination provisions as requiring heightened certification requirements, "it is automatically  
assumed that there are no or de minimis  risks to dolphins ."676 We consider that Mexico's argument 
fails to recognize that, even absent a designation under the determination provisions, pursuant to 
the 2016  Tuna Measure, all tuna products exported from, or offered for sale in, the United  States 
are subject to certification and tracking and verification requirements, regardless of the fishery from 
which they originate. Likewise, Mexi co's argument finds no support o n the Panel record or in the 
Reports of the Panels. The Panels, having reviewed the evidence on the record of risks to dolphins 
arising from the use of different fishing methods in different areas of the ocean, concluded that, at 
present, while some of the other fisheries manifested some risks to dolphins677, the vast majority of 
the wo rld's fisheries have a lower risk profile than the ETP large purse seine fishery.678 
6.202.   Moreover, the question before the Panels was not whether th e fisheries, other than the 
ETP large purse seine fishery, manifested any risk to dolphins. Rather the question be fore the Panels 
was whether the determination provisions, by imposing stricter certification and tracking and 
verification requirements in specific circumstances, allow the 2016  Tuna Measure to address similar 
risks in a similar manner, therefore ensuring that the 2016  Tuna Measure is properly calibrated to 
the risks to dolphins. The Panels answered this question and found that the determination provisions 
create flexibility "that helps to ensure that the 2016  Tuna Measure is calibrated to the different ris ks 
to dolphins arising from the use of different fishing methods in different areas of the ocean".679 
In light of the above analysis, we see no reason to disagree with this finding by the Panels.  
                                                
674 Panel Reports, para.  7.698 (referring to Dolphin Mortalities Per Set Due to ETP Dolphin Sets and in 
Other Fisheries (Panel Exhibit USA -111)).  
675 We understand that Mexico's main argument on appeal re peats its argument before the Panels that 
the 20 -year average (between 1997 -2017) artificially inflates the benchmark that the United  States relies on in 
applying its determination provisions. At the same time, as indicated in paragraph 6.196 above, Mexico  
explicitly stated that it was not challenging the Panels' discrete findings on the determination provisions where 
the Panels addressed the US  methodology. In any event, given the Panels' uncontested finding that the 
additional requirements imposed by the AIDCP had significantly reduced the extent of mortality and serious 
injury in the ETP large purse seine fishery, we see no reason to disagree with the Panels' explanation that, for 
the purpose of the determination provisions, it would be misleading to comp are, as Mexico suggests, the risk 
profile of the ETP in 2015, following the adoption of heightened certification and tracking and verification 
requirements pursuant to the AIDCP, with the risk profile of other fisheries that are not subject to similar 
requirements. (See Panel Reports, para.  7.699) Moreover, even under the 2009 -2015 data, with the exception 
of the Indian Ocean gillnet fishery, the Panels explained that, based on their review of the available evidence 
on the record, the other fisheries have a  lower risk profile than the ETP large purse seine fishery. (Panel 
Reports, paras.  7.441, 7.572, 7.685, and 7.699)  
676 Mexico's appellant's submission, para.  266. (emphasis original) In response to questioning at the 
hearing, Mexico acknowledged that the use  of "de minimis " in its argument may have overstated the issue. 
However, Mexico insisted that the point that it was making was that the determination provisions were 
deficient because they did not take into account certain relevant factors, such as the mor tality rates in a given 
fishery.  
677 Panel Reports, para.  7.541.  
678 Panel Reports, para.  7.700.  
679 Panel Reports, para.  7.691. See also ibid., para. 7.702.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.203.   In sum, we have found that the Panels adopted the correct approach in comparing the risk 
profiles of individual fisheries , because the certification requirements make a distinction on the basis 
of both fishing method and ocean area. Having found no legal e rror in the Panels' assessment of risk 
profiles, we consider that the Panels did not err in finding that the ETP large purse seine fishery has 
a special risk profile that distinguishes it from other fisheries. We have also addressed and rejected 
all of Mex ico's arguments challenging the Panels' assessment of the certification requirements , 
including the allegation that  the Panels did not take  into account the risks of inaccuracy  in their 
calibration analysis . 
6.204.   For all of these reasons, we find that Mexico ha s not demonstrated that the Panels erred in 
arriving at the intermediate finding that the different certification requirements are calibrated to the 
risks to dolphins arising from the use of different fishing methods in different areas of the ocean.680 
6.1.5.4   Tracking and verification requirements  
6.205.   Mexico claims that the Panels erred in finding that, although there remain differences 
between the NOAA and AIDCP regimes with respect to tracking and verification, such differences 
have been considerably narrowed in the 2 016 Tuna Measure , and that the remaining differences are 
calibrated to the differences  in the risk profile of the ETP  large purse seine fishery compared to other 
fisheries.681  
6.206.   As described in  section 5 above, the tracking and verificat ion requirements under  the 
2016 Tuna Measure concern the physical segre gation of dolphin -safe from non -dolphin -safe tuna, 
from the moment of harvest and throughout the entire processing chain.682 Specifically, the 
2016 Tuna Measure prescribes the documentation requirements for re cording and verifying 
segregation and the corresponding regulatory oversight. Like the certification requirements, the 
tracking and verification requirements distinguish between the ETP large purse seine fishery683 and 
all the other fisheries.684 
6.207.   We observe that Mexico's arguments on appeal, as well as the Panels' analysis of the tracking 
and verification requirements, make extensive reference to the evolution of the tracking and 
verification requirements under the 2016 Tuna Measure from those that were under  the 2013 Tuna 
Measure, in light of the first compliance panel and Appellate  Body fi ndings thereon. Accordingly, 
in order to situate the issue on appeal in its proper context, we provide a brief background of the 
tracking and verification requirements unde r the 2013 Tuna Measure and the first compliance panel 
and Appellate  Body's findings thereon. Next, we briefly describe the tracking and verification 
requirements under the 2016 Tuna Measure before summarizing the Panels' findings. Thereafter, 
we address M exico's claims that the Panels erred in making their findings on the tracking and 
verification requirements under the 2016 Tuna Measure.  
6.1.5.4.1   Summary of the findings from the first compliance proceedings regarding 
tracking and verification requirements under th e 2013 Tuna Measure  
6.208.   Under the 2013 Tuna Measure, the tracking and verification requirements primarily 
concerned the physical segregation of dolphin -safe from non -dolphin -safe tuna, from the moment 
of harvest and throughout the entire processing chain. Like  the 2016 Tuna Measure, the 2013 Tuna 
Measure prescribed the documentation requirements for recording and verifying segregation and the 
corresponding regulatory oversight. The first compliance panel observed that there were differences 
between the tracking  and verification requirements that applied to the ETP large purse seine fishery, 
on the one hand, which was governed by the AIDCP Tracking and Verification System, and all other 
fisheries, on the other hand. The first compliance panel considered that thes e differences related 
                                                
680 Panel Reports, para.  7.611.  
681 Mexico's Notice of Appeal, para.  9.c (referring to Panel Reports, paras.  7.650, 7.652, 
and 7.671 -7.676).  
682 Panel Reports, para.  7.613 (referring to 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.93(c)(1) -(3); Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , 
para. 6.12).  
683 Panel  Reports, paras.  7.56-7.61. See also 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.93(a) -(c)(1).  
684 Panel Reports, para.  7.62 (quoting United  States' first written submission to the Panels, para.  143). 
See also 2016  implementin g regulations (Panel Exhibits MEX -2 and USA -2), Sections  216.91(4) -(5) 
and 216.93(c)(2) -(3) and (d)(4).  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  "broadly to the depth, accuracy, and degree of government oversight of the tracking and verification 
systems".685  
6.209.   The first compliance panel used the word "depth" to refer to the point to which tuna can be 
traced back. According to the  first compliance panel, pursuant to the record -keeping requirements 
applicable to the ETP large purse seine fishery, tuna could be traced all the way back to the particular 
set in which the tuna was caught and the particular well in which it was stored.686 By contrast, in all 
other fisheries, tuna could only be traced back to the vessel and trip on which it was caught.687 
6.210.   The first compliance panel used the word "accuracy" to describe the degree to which a 
captain's (or, where applicable, observer's) statement  properly describes the lot of tuna to which it 
is assigned. The first compliance panel found that the accuracy attributable to the records required 
under the ETP large purse seine fishery was much more robust than that of the records required 
with respect  to all other fisheries.688 
6.211.   Finally, the first compliance panel used the term "government oversight" to refer to the 
extent to which a national, regional, or international authority was involved in the tracking and 
verification process. The first compliance panel found that, unlike in the other fisheries, in the 
ETP large purse seine fishery, information concerning every stage of the tuna catch and canning 
process was made available to national and regional authorities. Thus, these authorities were, in 
princi ple, able to verify at any stage of the catch and canning process whether a particular batch of 
tuna harvested in the ETP large purse seine fishery was dolphin -safe.689 
6.212.   Hence, the first compliance panel found that the differences in depth, accuracy, and 
government oversight showed that the tracking and verification system in place outside the 
ETP large purse seine fishery is less burdensome than that inside the ETP. Therefore, the first 
compliance panel found that the different tracking and verification requi rements modify the 
conditions of competition in the US tuna market to the detriment of like Mexican tuna and tuna 
products.690 The first compliance panel further concluded that the 2013  Tuna Measure was 
inconsistent with Article  2.1 of the TBT  Agreement because, inter alia , the United States had failed 
to show that the detrimental impact caused by the tracking and verification requirements stems 
exclusively from a legitimate regulatory distinction .691 
6.213.   On appeal, the Appellate  Body found certain flaws in the fir st compliance panel's reasoning 
underpinning its findings of inconsistency. With particular respect to the tracking and verification 
requirements, the Appellate  Body found, inter alia, that the first compliance panel's analysis had 
failed to encompass cons ideration of: (i)  the relative risks to dolphins from different fishing 
techniques in different areas of the oceans; and (ii)  whether the distinctions that the 2013 Tuna 
Measure  drew in terms of the different conditions of access to the dolphin -safe label were explained 
in light of the relative profiles. In addition, the Appellate  Body found that the first compliance panel 
had failed to take full account of the particular circumstances of this case. The Appellate  Body 
considered these circumstances to include the "design, architecture, revealing structure, oper ation, 
and application" of the 2013 Tuna Measure , as well as of the manner in which similar issues 
pertaining to the original Tuna Measure had been assessed in t he original proceedings.692 In making 
these findings, the Appellate  Body did not specifically review the first compliance panel's findings 
regarding the depth, accuracy, and government oversight of the tracking and verification 
requirements under the 2013 Tu na Measure.  
6.214.   However, following its review, the Appellate  Body still found that: (i)  the 2013  Tuna Measure 
modified the conditions of competition to the detriment of Mexican tuna products in the US market; 
(ii) such detrimental impact did not stem exclusive ly from a legitimate regulatory distinction; and 
                                                
685 First Compliance Panel Report, para.  7.354. (emphasis omitted)  
686 First Compliance Panel Report, para.  7.355 (referring to AIDCP, Resolution to Adopt t he Modified 
System for Tracking and Verification of Tuna (20  June 2001) (First Compliance Panel Exhibit  MEX-36)). 
687 First Compliance Panel Report, para.  7.356.  
688 First Compliance Panel Report, paras.  7.360 -7.363.  
689 First Compliance Panel Report, paras.  7.364-7.369.  
690 First Compliance Panel Report, paras.  7.370 and 7.382.  
691 First Compliance Panel Report, paras.  7.400 and 8.2.  
692 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.169.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  thus (iii)  the 2013 Tuna Measure accorded less favourable treatment to Mexican tuna products as 
compared to like tuna products from the United  States and other countries.693 
6.1.5.4.2   Summary of the Panels' findings reg arding tracking and verification 
requirements under the 2016 Tuna Measure  
6.215.   As described in  section 5 above, the tracking and verificatio n requirements under the 
2016 Tuna Measure prescribe the documentation requirements for recording and verifying 
segregation and the corresponding regulatory oversight. These requir ements distinguish between: 
(i) the ETP large purse seine fishery, which must comply with the AIDCP Tracking and Verification 
System694; and (ii)  all other fisheries, which must comply with the requirements prescribed in the 
2016 implementing regulations, refer red to as the "NOAA regime".695 Thus, the ETP large purse seine 
fishery is subject to the AIDCP regime, while all other fisheries are subject to the NOAA regime.  
6.216.   The Panels considered tha t the question before them was whether the distinctions with 
respect to tracking and verification made by the 20 16 Tuna Measure between the ETP  large purse 
seine fishery and all other fisheries are calibrated to the different risk profiles of the relevant 
fisheries.696 Regarding the difference in the risk profiles that the Panels took into account in their 
analysis, the Panels recalled their finding that "the ETP large purse seine fishery has a special risk 
profile that sets it apart from other fisheries arou nd the world ."697 
6.217.   The Panels recognized that the Appellate  Body had found fault with the first compliance 
panel's "segmented approach" to its analysis of the tracking and verification requirements under the 
2013 Tuna Measure. However, the Panels highlighted that the Appellate  Body had not found fault 
with the first co mpliance panel's conceptual approach to assessing the 2013 Tuna Measure's tracking 
and verification requirements. In particular, the Panels noted that the Appellate  Body had not 
criticized the first compliance panel for analysing the differences between th e different regimes from 
the perspective of depth, accuracy, and degree of government oversight . The Panels pointed out 
that, during the course of these compliance proceedings, the parties had themselves presented their 
arguments from the same perspective.  Therefore, being mindful of the Appellate  Body's criticism of 
the fact that the first compliance panel had failed to take "full account … of the manner in which 
similar circumstances pertaining to the original tuna measure had been assessed in the origina l 
proceedings"698, the Panels found it appropriate to follow the conceptual framework devised by the 
first compliance panel with respect to depth , accuracy , and degree of government oversight , in 
assessing the 2016  Tuna Measure .699 
6.218.   Regarding depth , the Panels found that, like the 2013 Tuna Measure, the 2016  Tuna Measure 
subjects the tuna caught in the ETP large purse seine fishery to the requirements of the AIDCP 
regime, whereby such tuna can be potentially traced back all the way to the particular set in which  
the tuna was caught and the particular well in which it was stored, or to a particular T TF, if the well 
or wells in which the tuna subject to the TTF was stored contained tuna from several sets. The Pa nels 
found that, under the NOAA  regime, following the amendments introduced in the 
2016 Tuna Measure regarding the new chain of custody record -keeping requirements, tuna can be 
traced back to one or more storage wells or other storage locations for a particular fishing trip. Thus, 
on the basis of the evidence  on the record, it appeared to the Panels that , under both the AIDCP 
and the NOAA regimes, it is possible to trac e tuna back to one or more wells in which it was stored. 
Accordingly, it seemed to the Panels that there is no longer any meaningful difference  with respect 
to the depth of the requirements between the AIDCP regime and the NOAA regime.700 
                                                
693 Appellate  Body Report, US – Tuna II (Mexico) (A rticle 21.5 – Mexico) , para.  8.1.a.viii. See also 
para. 1.11 above.  
694 Panel Reports, paras.  7.56-7.61. See also 2016  implementing regulations (Panel Exhibits MEX -2 and 
USA-2), Section  216.93(a) -(c)(1).  
695 Panel Reports, para.  7.62 (quoting United  States' first written submission to the Panels, para.  143). 
See also 2016  implementing regulations (Panel Exhibits MEX -2 and USA -2), Sections  216.91(4) -(5) 
and 216.93(c)(2) -(3) and (d)(4).  
696 Panel Reports, para.  7.651.  
697 Panel Reports, para.  7.652.  
698 Panel Reports, para.  7.622 (quoting Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.169).  
699 Panel Reports, paras.  7.622 and 7.653.  
700 Panel Reports, paras.  7.654 -7.656. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.219.   As regards accuracy , the Panels noted that , under the 2016  Tuna Measure, and , in particular, 
under the new NOAA regime chain of custody record -keeping requirement  for tuna products 
produced from "other fisheries", US  processors and importers of tuna or tuna products are now 
required to collect and retain, for two years, information on each point in the chain of custody of the 
tuna or tuna product. This information must be provided to the NMFS upon request and must be 
sufficient for the NMFS to conduct a trace -back of any product marketed as dolphin -safe to verify 
that the tuna product in fact meets the dolphin -safe labelling requirements. For the Panels, these 
modif ications seem to directly address the first compliance panel's concern that, under the 
2013 Tuna Measure, the accuracy attributable to the records required under the ETP large purse 
seine fishery had appeared to be much more robust  than that of the records required with respect 
to all other fisheries.701 
6.220.   Concerning government oversight , the Panels recalled that the first compliance panel had 
explained that , under the AIDCP regime, information concerning every stage of the tuna catch and 
canning process is made available to national and regional authorities, which must be sent copies of 
TTFs and are thus able to verify at any stage of the catch and canning process whether a particular 
batch of tuna is dolphin -safe. By contrast, the first comp liance panel had expressed concern with 
respect to the inability of the US  government under the NOAA regime to go "behind the documents" 
in order to verify the movements of the tuna prior to its arrival at the cannery.702  
6.221.   The Panels noted that the 2016  Tuna Measure maintains the requirement, under the 
2013 Tuna Measure, that US  tuna processors submit monthly reports to the US  Tuna Tracking and 
Verification Program  for all tuna received at their processing facilities. At the same time, the Panels 
noted that t he new NOAA regime chain of custody record -keeping requirement for tuna products 
harvested  from "other fisheries", referred to in paragraph  6.219 above, addresses the previous 
inability of the US  government under the NOAA regime to go "behind the documents ", because NMFS 
now has the ability to check the information on the movement of the tuna, even before it arrives at 
the cannery. For the Panels, this modification seems to bridge the previous existing difference 
between the AIDCP regime and the NOAA regime .703 
6.222.   However, with particular respect to the delegation of responsibility for developing tracking 
and verification systems, the Panels noted that differences remained between the two regimes. The 
Panels observed that , under the AIDCP regime, the Secretariat704 brokers requests for the data and 
documentation that would allow a party to obtain information from processors of another party 
sufficient to trace back a tuna product through its chain of custody to the harvesting vessel and 
trip.705 By contrast, the Panel s agreed with Mexico that the process of collecting and keeping the 
information under the NOAA regime still seems to rely heavily on importers and processors. 
Moreover, under the 2016  Tuna Measure, the degree of government oversight of the catch and 
proces sing operations that take place outside the United  States seemed to the Panels to be 
somewhat limited.706 
6.223.   Thus, the Panels considered that , although the 2016  Tuna Measure had narrowed the 
differences between the AIDCP and the NOAA regimes in several aspects of the tracking and 
verification requirements, there were st ill differences between the two  regimes regarding the extent 
of government oversight. In assessing the legal significance of these differences, the Panels noted 
that the measure may be calibrated to the risks to dolphins where it uses a more sensitive 
mechanism in areas where risks are h igh but a less sensitive mechanism in areas where the risks 
are low. The Panels considered that, owing to the special risk profile of the ETP large purse seine 
fishery, "it is calibrated" for the 2016 Tuna Measure to apply less strict (i.e. less sensitive)  
requirements with respect to  fisheries other than the ETP large purse seine fishery and to pose 
stricter (i.e. more sensitive) requirements inside the ETP large purse seine fishery.707 For the Panels, 
                                                
701 Panel Reports, para.  7.657 (referring to First Compliance Panel Report, paras.  7.360 -7.361).  
702 Panel Reports, paras.  7.658 -7.660 (referring to First Compliance Panel Report, paras.  7.364 -7.368).  
703 Panel Reports, paras.  7.661 -7.663.  
704 The word "Secret ariat" refers to the staff of the IATTC. (International Dolphin Conservation Program, 
System for Tracking and Verifying Tuna, as amended (2015) (Panel Exhibit USA -90), Section  1.i.) 
705 Panel Reports, para.  7.665 (referring to International Dolphin Conservat ion Program, System for 
Tracking and Verifying Tuna, as amended (2015) (Panel Exhibit USA -90), Section 7).  
706 Panel Reports, paras.  7.664 -7.666.  
707 Panel Reports, para. 7.671.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the differences in the requirements are commensurate wit h the difference in the risks to dolphins 
arising from the use of different fishing methods in different areas of the ocean.708 
6.224.   Moreover, in the Panels' view, the determination provisions create flexibility that enables the 
2016 Tuna Measure to treat similar  situations similarly. According to the Panels, the determination 
provisions work together with the tracking and verification requirements to ensure that the 
2016 Tuna Measure is calibrated to the risks to dolphins arising from the use of different fishing  
methods in different areas of the ocean.709 
6.225.   The Panels also took note of Mexico's contention that a number of the countries that are the 
largest suppliers of tuna and tuna products, such as the Philippines, Chinese  Taipei, and Thailand 
are significantly def icient in the control and monitoring of fishing activities and have been identified 
as extremely vulnerable to IUU fishing. However, the Panels recalled that the NOAA regime provides 
that breaches of the tracking and verification requirements may lead to t he imposition of sanctions. 
In particular, sanctions for offering for sale or export tuna products falsely labelled as dolphin -safe 
may be assessed against any producer, importer, exporter, distributor, or seller who is subject to 
the jurisdiction of the U nited States . Thus, even in the absence of jurisdiction by the US  Department 
of Commerce to audit foreign fishing vessels, carrier vessels, and foreign processors , or vulnerability 
to IUU fishing in some countries, the Panels considered that the United  States, through the 
2016 Tuna Measure, has the necessary tools to induce compliance of US  processors and 
importers.710 
6.226.   For these reasons, the Panels found that , although there remained differences between the 
NOAA and AIDCP regimes with respect to tracking and verification, such differences had been 
considerably narrowed in the 2016  Tuna Measure. The Panels also found that these remaining 
differences are calibrated to the differences in the risk profile of the ETP large purse seine fishery 
compared to other fish eries.711  
6.1.5.4.3   Legal analysis  
6.227.   Mexico contends that the Panels erred in their calibration analysis of the tracking and 
verification requirements: (i)  by rejecting the reliability of reporting and fisheries management as 
relevant to evaluating the calibration of t he tracking and verification requirements, and by finding 
that the measure can be considered calibrated where it allows higher margins of error for 
certifications in all ocean areas other than the ETP712; (ii) by finding that the determination 
provisions con tribute to the calibration of the measure713; and (iii)  by applying an incorrect analysis 
to conclude that differences between the requirements for the ETP large purse  seine fishery and 
other fisheries have been narrowed.714 In addition, Mexico contends that the Panels acted 
inconsistently with Article  11 of the DSU by refusing to give any consideration to evidence that, 
according to Mexico, was directly relevant and material to the outcome of the Panels' legal 
analysis.715 
6.228.   The United  States posits that Mexico's  challenge to the Panels' evaluation of the tracking 
and verification requirements should be dismissed. The United  States argues that: (i)  the Panels did 
not omit any relevant factors in their assessment of whether the 2016  Tuna Measure is calibrated 
to the risk profiles of different fishing methods in different ocean areas716; (ii) Mexico's claim against 
the Panels' reasoning concerning the determination provisions contributing to the calibration of the 
tracking and verification requirements should be reject ed717; and (iii)  Mexico puts forward no reason 
as to why the Panels' analysis of the differences between the AIDCP and NOAA tracking and 
                                                
708 Panel Reports, paras.  7.671 -7.673.  
709 Panel Reports, para.  7.674.  
710 Panel Reports , para.  7.675.  
711 Panel Reports, para.  7.676.  
712 Mexico's appellant's submission, paras.  275-277. 
713 Mexico's appellant's submission, para.  280. 
714 Mexico's appellant's submission, paras.  285-299. Mexico also argues that the Panels' calibration 
analysis is fla wed, owing to alleged errors in the Panels' assessment of risk profiles. (Mexico's appellant's 
submission, paras. 273 -274) We recall that these arguments were addressed in section 6.1.4 above.  
715 Mexico's Notice of Appeal, para.  9.c (referring to Panel Repo rts, paras.  6.57 and 7.656); appellant's 
submission, para.  306. 
716 United  States' appellee's submission, para.  281. 
717 United  States' appellee's submission, para.  300. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  verification regimes constitutes legal error.718 The United  States further asserts that Mexico's claim 
under Article  11 of the DSU should be rejected.719 
6.229.   We begin with Mexico's allegation that the Panels erred in their calibration analysis by failing 
to take into account several relevant criteria including "the sufficiency of regulatory oversight, the 
reliability of reporting, t he existence of IUU fishing and the existence of transshipment at sea".720 
Instead, according to Mexico, the Panels erroneously based their calibration analysis on "the 
likelihood of AIDCP -compliant setting on dolphins in the ETP producing dolphin -safe and n on-dolphin 
safe tuna compared to the likelihood in all other fisheries  … and the perceived 'margin of error' in 
the label associated with such likelihood".721 
6.230.   As a preliminary observation, we note that, by referring to "AIDCP -compliant setting on 
dolphins in  the ETP", Mexico's argument seems to suggest that the Panels examined the tracking 
and verification requirements through the lens of the AIDCP regime. We recall that the AIDCP applies 
only to the ETP. While the 2016  Tuna Measure applies the AIDCP Tracking  and Verification System 
to the ETP large purse seine fishery, the 2016  Tuna Measure does not apply the AIDCP system to 
the other fisheries in the ETP. Instead, the other fisheries are subject to the NOAA regime. Thus, 
the Panels were not focused on what d istinctions manifested between AIDCP -compliant methods and 
non-AIDCP -complian t methods. Rather, in our view, the Panels rightly focused their analysis on the 
distinctions in the tracking and verification requirements under the 2016  Tuna Measure, taking 
account of the differences in the risk profiles of the different fisheries. We recall that, having assessed 
the risk profiles of the individual fisheries, the Panels established  that, when compared to the 
ETP large purse seine fishery, which has a "special ri sk profile", all the other fisheries are similar in 
their risk profiles insofar as in none of them is setting on dolphins practised consistently or 
systematically.722 
6.231.   Turning to Mexico's assertion that "[t]he Panels' reasoning regarding the margin of error 
suffered from the same errors identified above in respect of the risks of inaccurate information and 
the certification requirements", we recall that we addressed these arguments in  section 6.1.5.3 
above. Thus, our discussion in  paragraphs  6.187 -6.189  above applies equally to our review of the 
Panels' reasoning in their evaluation of the tracking and verification requirements.  
6.232.   Moreover, specifically in their evaluation of the tracking and verification requirements, the 
Panels explained that:  
In our view, the difference in the risk profile of the ETP large purse seine fishery 
compared to other fisheries indicates that there is a greater likelihood that a vessel in 
the ETP large purse seine fishery will produce both dolphin -safe and non -dolphin -safe 
tuna on any fishing trip, and that the two groups of tuna will have to be segregated and 
tracked. Conversely, there would be a lower likelihood that a set produces 
non-dolphin -safe tuna in other fisheries that would need to be segregated as a 
consequence of this. This  justifies, in our view, the need for a stricter regime of tracking 
and verification in the ETP large purse seine fishery. … We thus consider that it is 
reasonable for the United  States to apply a more sensitive tracking and verification 
mechanism in respe ct of high -risk fisheries. Doing so is "commensurate with" the risks 
to dolphins arising from the use of different fishing methods i n different areas of the 
ocean .723 
6.233.   We share the Panels' view as quoted above. The key question before the Panels was whether 
the differences in the sensitivity  of the labelling conditions  are properly calibrated to the differences 
in risk profiles of the fisheries. If the sensitivity of the labelling conditions is calibrated to the risks 
to dolphins arising from the use of diffe rent fishing methods in different areas of the ocean, then the 
2016 Tuna Measure addresses these different levels of risks to dolphins in such a way as to ensure 
                                                
718 United  States' appellee's submission, para.  281. 
719 United  States' appellee's submission,  para. 281. 
720 Mexico's appellant's submission, para.  278. 
721 Mexico's appellant's submission, para.  278. See also ibid., paras.  275-277. 
722 See para. 6.177 above.  
723 Panel Reports, para.  7.672.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  accurate labelling (i.e. less sensitive requirements in fisheries with lower risks, and more s ensitive 
requirements in fisheries with higher risks).  
6.234.   This leads us to Mexico's contention that the Panels erred by completely omitting the 
sufficiency of regulatory oversight, the reliability of reporting, the existence of IUU  fishing , and the 
existence of trans -shipment at sea as criteria for their calibration assessment.724 As we explain 
below, Mexico's contention fails to take into account the Panels' explanations regarding these factors.  
6.235.   First, concerning government oversight, the  Panels noted that the new NOAA  regime chain 
of custody record -keeping requirement for tuna products harveste d from other fisheries, referred to 
in paragraph  6.219  above, addresses the previous inability of t he US  government under the 
NOAA  regime to go "behind the documents", be cause NMFS now has the ability to check the 
information of the movement of the tuna, even before it arrives at the cannery. For the Panels, this 
modification seemed to bridge the previous existing difference between the AIDCP regime and the 
NOAA regime.725 In response to questioning at the hearing, Mexico accepted that the new 
custody -keeping requirements under the 2016 Tuna Measure appeared to have narrowed the 
differences between the AIDCP regime and the NOAA regime. However, Mexico stressed that the 
differences had not been eliminated.  
6.236.   We recall that the calibration analysis is not intended to test for uniformity in the 
requirements applicable to the different fisheries. Rather, the sensitivity of the labelling conditions 
under the 2016 Tuna Measure should be calibrated to the risks to dolphins arising from the use of 
different fishing methods in different areas of the ocean. Thus, requiring the 2016 Tuna Measure to 
be calibrated to the risks to dolphins does not mean that the differences between the AIDCP r egime 
and the NOAA regime must be eliminated under the 2016 Tuna Measure, given that the ETP large 
purse seine fishery has a special risk profile that distinguishes it from other fisheries.  
6.237.   Second, the Panels took note of Mexico's contention that a number of the countries that are 
the largest suppliers of tuna and tuna products, such as the Philippines, Chinese  Taipei, and Thailand 
are significantly deficient in the control and monitoring of fishing activities, and have been identified 
as extremely vulnerab le to IUU fishing. Mexico had also argued that the US  Department of 
Commerce lacks jurisdiction to audit foreign fishing vessels, carrier vessels, and foreign processors. 
However, as indicated in paragraph  6.225  above , the Panels recalled that the NOAA reg ime provides 
that breaches of the tracking and verification requirements may lead to the imposition of sanctions. 
Thus, even in the absence of jurisdiction by the US  Department of Commerce to audit foreign fishing 
vessels, carrier vessels, and foreign proc essors, or vulnerability to IUU fishing in some countries, 
the Panels considered that the United  States, through the 2016  Tuna Measure, has the necessary 
tools to induce compliance of US  processors and importers.726 
6.238.   Thus, contrary to Mexico's arguments, in t heir calibration analysis , the Panels did not 
"completely omit[] the sufficiency of regulatory oversight, the reliability of reporting, the existence 
of IUU fishing and the existence of transshipment at sea".727 Still in this regard, and as discussed in 
paragraph  6.147  above, we do not exclude the possibility that the above -mentioned factors 
highlighted by Mexico may affect the ultimate accuracy of the dolphin -safe label. Such risks of 
inaccuracy are relevant to the assessment of whether the measure is ca librated to the risks to 
dolphins. However, as the United  States suggests728, it was incumbent upon Mexico to provide 
relevant evidence in support of its assertion that , in fisheries where factors affecting regulatory 
reliability persist, there is an increas ed risk that the labels for tuna products would not accurately 
reflect the dolphin -safe nature of those products. Mexico has pointed to no evidence on the Panel 
record that pertains specifically to the risk of inaccurate labelling under the 2016 Tuna Measu re, 
owing to "the sufficiency of regulatory oversight, the reliability of reporting, the existence of 
IUU fishing and the existence of transshipment at sea".729 Nor has Mexico identified any evidence 
on the Panel record that would suggest that these fa ctors undermine the ability "of  the 
                                                
724 Mexico's appellant's submission, para.  278. 
725 Panel Reports, paras.  7.661 -7.663.  
726 Panel Reports, para.  7.675.  
727 Mexico's appellant's submission, para.  278. 
728 United  States' appellee's submission, para.  53 and fn  122 thereto.  
729 Mexico's appellant's submission, para.  278. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  US government under the NOAA regime to go 'behind the documents' in order to verify the 
movements of the tuna prior to the arrival to the cannery".730 
6.239.   With respect to the determination provisions, Mexico contends that the Panels  erred in 
finding that the determination provisions create flexibility that enables the 2016  Tuna Measure to 
treat similar situations similarly. In support of its contention, Mexico relies on the arguments that it 
made in connection with the Panels' calibr ation analysis of the certification requirements.731 
We recall that we addressed these arguments in section  6.1.5.3  above. Thus, our discussion in  
paragraphs  6.192 -6.202  above  applies equally to our review of the Panels' reasoning in their 
evaluation of the tracking and verification requirements. In particular, we note that Mexico relies on 
its argument regarding the relevance of PBR evidence, which we have rejected above. Furt hermore, 
we do not share Mexico's view that the Panels relied on inconsistent sets of data in assessing the 
eligibility criteria, on the one hand, and the application of the determination provisions, on the other 
hand.  
6.240.   We now turn to Mexico's argument that  the Panels applied a faulty analysis to conclude that 
the 2016  Tuna Measure had narrowed the differences between the requirements for the ETP large 
purse seine fishery and the other fisheries.732 Mexico relies heavily on the findings of the first 
compliance  panel to argue that the different approach taken by the Panels in these compliance 
proceedings is faulty.733 However, we note that the first compliance panel was addressing a different 
measure that did not incorporate: (i)  the new custody record -keeping req uirements that introduce 
a legal requirement that can be enforced through the sanctions exist ing in the measure; (ii)  the new 
Captain Training Course available online in nine  languages; and (iii)  the amended determination 
provisions.  
6.241.   Specifically , Mexico h ighlights that the first compliance panel, in addressing the "accuracy" 
of the NOAA regime, found that the United  States had "submitted no evidence showing that 
canneries actually do ensure that the tuna they receive matches a particular captain 's statemen t".734 
The first compliance panel also considered that the United  States  had "not provided any evidence 
explaining how canneries are able to ensure that captains' certifications remain with the tuna batches 
they identify throughout this process".735 Moreover, the first compliance panel considered that, 
under the 2013 Tuna Measure, "there [did] not appear to be any legal requirement that the canneries 
verify the accuracy of the records, or that the records in fact correctly describe the particular batches 
of tun a to which they are assigned ."736 Contrary to Mexico's suggestion that the Panels did not pay 
attention to the first compliance panel's findings, the Panels in these compliance proceedings 
explicitly took into account these findings identified by Mexico737 and explained why the 
2016 Tuna Measure addressed the first compliance panel's concerns. The Panels stated:  
We note, however, that under the 2016  Tuna Measure, and in particular, under the new 
chain of custody record -keeping requirements for tuna products pro duced from "other 
fisheries", this situation has changed . Specifically, US  processors and importers of tuna 
or tuna products are now required to collect and retain, for two years, information on 
each point in the chain of custody of the tuna or tuna produc t and this information must 
be provided to the NMFS upon request and must be sufficient for the N MFS to conduct 
a trace -back of any product marketed as dolphin -safe to verify that the tuna product in 
fact meets the dolphin -safe labelling requirements. Thus , these modifications seem to 
directly address the first compliance panel's concerns with the 201 3 Tuna Measure, in 
particular, because they require US  processors and importers of tuna or tuna products 
to collect and retain information on each point in the  chain of custody of the tuna or 
tuna product.738 
                                                
730 Panel Reports, para. 7.660.  See also ibid., paras.  7.659 -7.663.  
731 Mexico's appellant's submission, paras.  279-280. 
732 Mexico's appellant's submission, paras.  285 and 299.  
733 We note that the findings of the first compliance panel that Mexico seeks to rely on were not the 
subject of a ppeal in the first compliance proceedings.  
734 Mexico's appellant's submission, para.  288 (quoting First Compliance Panel Report, para.  7.361).  
735 Mexico's appellant's submission, para.  289 (quoting First Compliance Panel Report, para.  7.362).  
736 Mexico's appe llant's submission, para.  290 (referring to First Compliance Panel Report, para.  7.363).  
737 Panel Reports, para.  7.657.  
738 Panel Reports, para.  7.657. (emphasis added)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.242.   In addition , we note that Mexico refers to the first compliance panel's "government 
oversight" findings.739 Mexico points to the first compliance panel's statement that , under the 
2013 Tuna Measure, the United  States had to rely on the canneries for information about the 
movement of the tuna prior to its arrival at the cannery and was not ab le to go "behind the 
documents"  to verify that a particular dolphin -safe certification describes t he batch of tuna with 
which it is associated.740 However, the first compliance panel explained that it had seen "no evidence 
suggesting that canneries and other importers in fact do this, and, as [it understood]  the measure, 
canneries and other importers are  not legally required  to conduct such checks".741 
6.243.   We observe that the Panels in these compliance proceedings expressly took account of the 
first compliance panel's findings in this regard.742 The Panels identified the main concern of the first 
compliance panel  with respect to government oversight as the inability of the US  government under 
the NOAA regime to go "behind the documents" in order to verify the movements of the tuna prior 
to its arrival at the cannery.743 The Panels then explained how, in their view, the modifications under 
the 2016  Tuna Measure addressed these concerns. Specifically, the Panels stated:  
Under the modifications in 50  CFR 216.91(a)(5), US  processors and importers of tuna 
or tuna products from such "other fisheries" are now required to co llect and retain, for 
two years, information on each point in the chain of custody of the tuna or tuna product 
... This information must be provided to the NMFS upon request and must be sufficient 
for the NMFS to conduct a trace -back of any product markete d as dolphin -safe to verify 
that the tuna product in fact meets the dolphin -safe labelling requirements. To us, this 
addresses the previous inability of the US  government under the NOAA regime to go 
"behind the documents", as NMFS will have the ability to check the information of the 
movement of the tuna, even before it arrives at the cannery. Indeed, these 
modifications require US processors and importers to have information relating to the 
storage facilities, trans -shippers, processors, and wholesalers/di stributors of tuna, and 
such information must be sufficient for the NMFS to trace any non -dolphin -safe tuna 
loaded onto the harvesting vessel back to one or more storage wells or other storage 
locations. Therefore, the US  government may now go behind the d ocuments  and check 
the movements of the tuna along the various steps of the catch and processing of 
tuna.744 
6.244.   Thus, contrary to Mexico's arguments, we consider that the Panels in these compliance 
proceedings followed the Appellate  Body's guidance by taking fu ll account of the "particular 
circumstances" of this case, including "the manner in which similar circumstances" pertaining to the 
2013 Tuna Measure had been assessed in the first compliance proceedings.745 Moreover, on the 
basis of our above review of the P anels' reasoning, we share their view that the amendments 
incorporated in the 2016 Tuna Measure – including (i)  the new custody record -keeping requirements 
that introduce a legal requirement that can be enforced through the sanctions existing  in the 
measur e; (ii)  the new Captain Training Course available online i n nine  languages; and 
(iii) the amended determination provisions – have narrowed the differences between the AIDCP and 
NOAA regimes.746 
6.245.   Finally, Mexico considers that the Panels' finding that the diff erences between t he AIDCP and 
NOAA regimes have been "narrowed" in the 2016  Tuna Measure is faulty because the Panels did not 
comply with their duty under Article  11 of the DSU by failing to take into account the evidence 
contained in Panel Exhibit MEX -127.747 Specifically, Mexico challenges the following finding of the 
Panels, contained in the interim review section of their Reports:  
Mexico requests that a sentence be added … to better describe Mexico's argument 
regarding the complex supply chain for tuna by  referring to evidence submitted by 
                                                
739 Mexico's appellant's submission, para.  292. 
740 Mexico's appellant's submission, para.  293 (quoting First Compliance Panel Report, para.  7.365).  
741 Mexico's appellant's submission, para.  294 (quoting First Compliance Panel Report, para.  7.368 
(emphasis original)).  
742 Panel Reports, paras.  7.658 -7.664.  
743 Panel Reports, para.  7.659.  
744 Panel Reports, para.  7.662. (emphasis added)  
745 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.169.  
746 Panel Reports, paras.  7.670 and 7.676.  
747 Mexico's appellant's submission, para.  305. See also ibid., paras. 300 -304. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  Mexico on this point, namely, a recent report of the International Seafood Sustainability 
Foundation. … We note that the argument that Mexico r equests the Panels to 
reflect  … pertains to the issue of whether tuna compani es are able to track a particular 
catch to the individual vessel that caught it and to other points in the supply chain. The 
present proceedings, however, concern whether the 2016  Tuna Measure is calibrated to 
different levels of risks posed to dolphins by  different fishing methods in different parts 
of the ocean, among others, in terms of its tracking and verification requirements. 
Therefore, the argument that Mexico requests us to reflect in the paragraph at issue is 
not directly relevant to our inquiry. We therefore deny Mexico's request.748 
6.246.   Article  11 of the DSU provides, in relevant part, that "a panel should make an objective 
assessment of the matter before it, including an objective assessment of the facts of the case ." 
As the Appellate  Body has explained, in accordance with Article  11, a panel is required to "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".749 Within these param eters, "it is generally within the 
discretion of the [p]anel to decide which evidence it chooses to utilize in making findings"750, and 
the mere fact that a panel did not explicitly refer to each and every piece of evidence in its reasoning 
is insufficient t o establish that the panel applied an improper standard of review.751 
6.247.   Turning to the claim before us, we note that, on appeal, Mexico refers to the content of Panel 
Exhibit MEX -127752 to argue that , if market participants sourcing tu na from the Western and 
Central Pacific and the Indian Ocean s are unable to track tuna to the vessel from which it was caught, 
the differences between the requirements for tuna sourced from large purse seine vessels in the ETP 
and tuna from those other ocean areas cannot, as the Pan els found, have been "narrowed".753 
6.248.   We note that Panel Exhibit MEX -127 is a document produced by the International Seafood 
Sustainability Foundation ( ISSF) entitled Regional Fishery Management Organization ( RFMO ) Catch 
Documentation Schemes: A Summary . This document defines catch documentation schemes (CDSs) 
as: 
[G]lobal traceability systems that certify a unit of legal catch, providing a catch 
certificate (CC) to the legal owner of the fish (at the point of capture) and then trace 
the movement of this unit o f catch from unloading through international trade (export 
and re -export), into the end market (the first point of sale/import).754 
6.249.   The document explicitly states that it "provides an overview of the current activities 
regarding the development, implementati on, review and amendm ent of CDS by RFMOs and the 
FAO Technical Consultation on the Development of Voluntary Guidelines for CDS".755 Indeed, in 
opting not to rely on this exhibit, the Panels explained that Mexico's argument in connection with 
Panel Exhibit ME X-127 pertained to the "complex supply chain for tuna"  and "to the issue of whether 
tuna companies are able to track a particular catch to the individual vessel that caught it and to 
other points in the supply chain".756 However, the Panels highlighted that these compliance 
                                                
748 Panel Reports, para.  6.57. 
749 Appellate  Body Reports, China – Rare Earths , para.  5.178; Brazil – Retreaded Tyres , para.  185 
(referring to Appellate  Body Report, EC – Hormones , paras.  132-133). See also Appellate  Body Reports, 
Austra lia – 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. 
750 Appellate  Body Reports, EU – Fatty Alcohols (Indonesia) , para.  5.87; China – Rare Earths , 
para. 5.178; EC – Hormones , para.  135. 
751 Appellate  Body Reports, EU – Fatty Alcohols (Indonesia) , para.  5.87; EC – Fasteners (China) , 
paras.  441-442; Brazil – Retreaded Tyres , para.  202. 
752 Mexico's appellant's submission, para.  300 (referring to ISSF, RFMO Catch Documentation Schemes: 
A Summary  (Washington, DC, 14  September 2016) (Panel Exhibit MEX -127), paras.  1 and 9).  
753 Mexico's appellant's submission, para.  305. 
754 ISSF, RFMO Catch Documentation Schemes: A Summary  (Washington, DC, 14  September 2016) 
(Panel Exhibit MEX -127), para.  1. See also United  States' appellee's submission, para.  335. 
755 ISSF, RFMO Catch Documentation Schemes: A Summary  (Washington, DC, 14  September 2016) 
(Panel Exhibit MEX -127), para.  3. 
756 Panel Reports, para.  6.57. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  proceedings concern whether the 2016  Tuna Measure, including the tracking and verification 
requirements, is calibrated to different levels of risks posed to dolphins by different fishing methods 
in different parts of the ocean. Therefore, the Panels considered that the information that Mexico 
sought to rely on in Panel Exhibit MEX -127 was not directly relevant to their inquiry.757 
6.250.   Mexico appears to draw a correlation between the experiences of CDSs recorded in Panel 
Exhibit MEX -127 and the po tential operation of the 2016 tracking and verification requirements.758 
However, Mexico has provided no reasons for such a correlation, especially given that the data point 
for certification under a CDS, by "unit of legal catch", is not applicable to either  the AIDCP or NOAA 
regimes.759 Rather, as the Panels in these compliance proceedings found, unlike a CDS, both the 
AIDCP and NOAA regimes under the 2016 Tuna Measure require that the records that accompany 
the tuna from harvest through processing must be suf ficient to allow the verification or "trace -back" 
of the tuna products to the storage wells of a particular vessel for each fishing trip.760 Moreover, to 
the extent that the 2016  Tuna Measure applies the AIDCP Tracking and Verification System with 
respect to  the ETP large purse seine fishery, we note that Panel Exhibit MEX -127 contains a 
discussion of the AIDCP. The document states that the AIDCP "does not track all yellowfin catch 
from all gears nor all parties fishing for yellowfin tuna in the eastern Pacif ic Ocean and as such is 
not a true CDS".761 Thus, our review of the content of Panel Exhibit MEX -127 suppor ts the 
Panels'  view that Mexico's arguments  regarding CDSs, contained in this exhibit, was not relevant to 
the Panels' c alibration analysis of the 2016  Tuna Measure.  
6.251.   For these reasons, we find that Mexico has not demonstrated that  the Panels failed to make 
an objective assessment of the facts of the case as required under Article  11 of the DSU by omitting 
Panel Exhibit MEX -127 from their analysis of the tracking and verification requirements.  
6.1.5.4.4   Conclusion for tracking and verification requirements  
6.252.   As with the certification requirements, we have found that , with respect to the tracking and 
verification requirements, the Panels adopted the correct approach in  comparing the risk profiles of 
individual fisheries, because these requirements make a distinction on the basis of both fishing 
method and ocean area. Having found no legal error in the Panels' assessment of risk profiles, we 
consider that the Panels did not err in finding that it is both the technical and legal possibilit ies of 
setting on dolphins and the fact that dolphin sets occur in a consistent and systematic manner in 
the ETP large purse seine fishery that give this fishery its special risk profile. Moreover, we have 
rejected Mexico's claims that: (i)  the Panels erred i n their evaluation of the tracking and verification 
requirements , including the allegation that the Panels did not take into account the risks of 
inaccuracy ; and (ii)  the Panels failed to make an objective assessment of the facts of the case as 
required un der Article  11 of the DSU. Consequently, we find that Mexico has not demonstrated that 
the Panels erred in arriving at the intermediate finding that:  
[A]lthough there remain differences between the NOAA and AIDCP regimes with respect 
to tracking and verifi cation, the Panels are of the view that such differences have been 
considerably narrowed in the 2016  Tuna Measure and the Panels find that the remaining 
differences are calibrated to the differences in the risk profile of the ETP large purse 
seine fishery compared to other fisheries.762 
6.1.5.5   The 2016 Tuna Measure "as a whole"  
6.253.   Mexico argues that, because the Panels' reasoning of the 2016  Tuna Measure as a whole 
was based entirely  on their findings and c onclusions with respect to the calibration of the eligibility 
criteria, the certification requirements, and the tracking and verification requirements, respectively, 
all of the erro neous findings  made in those assessments flowed through and were the exclusive basis 
for the Panels' assessment  of the measure as a whole . Accordingly, Mexico contends that the Panels 
                                                
757 Panel Reports, para.  6.57. 
758 Mexico's appellant's submission, para.  305. 
759 United  States' appellee's submission, paras.  335-337. 
760 Panel Reports, paras.  7.57-7.59 and 7.63 -7.66. See also United  States' appellee's submission, 
para. 336. 
761 ISSF, RFMO Catch Documentation Schemes: A Summary  (Washington, DC, 14  September 2016) 
(Panel Exhibit MEX -127), para.  22. 
762 Panel Reports, para.  7.676.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  incorrectly assessed the calibration and consistency with Article  2.1 of the TBT  Agreement of the 
2016 Tuna Measure as a whole.763 
6.254.   The United  States posits that the Panels' intermediate conclusions concerning the  eligibility 
criteria, certification requirements, and tracking and verification requirements were correct and not 
in error. In addition, the United  States submits that, contrary to Mexico's arguments, the 
Panels'  intermediate conclusions were not the excl usive basis for the Panels' overall assessment of 
the measure as a whole. The United  States indicates that the Panels also considered how the 
different parts of the measure interact to address the risk s to dolphins arising from different fishing 
methods in  different ocean areas, and explained how the components of the measure 
"work  together" to "achieve the objectives of the 2016  Tuna Measure".764 
6.255.   We have found above that Mexico has failed to demonstrate that the Panels erred in their 
evaluation leading to th eir intermediate findings regarding the calibration of the eligibility criteria, 
certification requirements, and tracking and verification requirements. We recall that analysing the 
measure in a sequential manner does not, in itself, render the analysis er roneous, provided that 
such sequential analysis does not "lead to the isolated consideration of a particular element " where 
the elements of a measure are closely interrelated.765 
6.256.   Based on a review of the Panels' examination of the 2016  Tuna Measure, we consi der that 
the Panels took into account the "cumulative and highly interrelated" nature of the different aspects 
of the 2016  Tuna Measure. For instance, the Panels repeatedly noted that the determination 
provisions work together with and reinforce the certif ication and tracking and verification 
requirements. Therefore, the Panels' consideration of the certification and tracking and verification 
requirements included a consideration of the determination provisions.766 As a second example, the 
Panels found that t he certification requirements, including the newly introduced Captain Training 
Course, are "embedded within a sufficiently enforceable regulatory framework", referring to the 
tracking and verification requirements.767 Furthermore , the Panels synthesized thei r findings about 
the various elements of the measure, "taking into account the important interlinkages among such 
elements".768 In this regard, the Panels explained that:  
Without the certification, and tracking and verification requirements, as well as the 
determination provisions, however, the distinction made through the eligibility criteria 
would not have achieved the Measure's objective of dolphin protection. In our view, the 
interlinkage among these four elements of the Measure is so crucial that withou t one of 
them the 2016  Tuna Measure, as we know it, could not function. We see the 
certification, and the tracking and verification requirements, as well as the 
determination provisions, as tools that enforce the eligibility criteria with a view to 
achievi ng the objective of protecting dolphins from harmful fishing methods.769 
6.257.   We thus consider that the Panels' analyses of e ach of the elements of the 2016  Tuna 
Measure, as well as their examination of the measure as a whole , were properly informed by the 
interlinkages between these elements and the fact that they operate together to regulate access to 
the dolphin -safe label. Furthermore, we recall that Mexico's appeal in this regard is consequential 
upon its challenge of the Panels' assessment of the eligibility criteria, certification requirements, and 
tracking and verification requirements. Having reviewed and rejected Mexico's arguments against 
the Panels' assessment of each of these elements of the 2016 Tuna Measure, we fi nd that Mexico 
has not demonstrated that the Panels erred in their assessment of the 2016  Tuna Measure, as a 
whole, or in finding that the 2016  Tuna Measure, as a whole, is calibrated to the risks to dolphins 
arising from the use of different fishing metho ds in different areas of the ocean.770 
                                                
763 Mexico's appellant's submission, para.  307 (referring to Panel Reports, paras.  7.703 -7.717).  
764 United  States' appellee's submission, para.  353 (quoting Panel Reports, paras.  7.711 and  7.713; 
referring to ibid., paras. 7.709 and 7.712).  
765 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.15. 
766 Panel Reports, paras.  7.530, 7.609 -7.610, and 7.674.  
767 Panel Reports, para.  7.593.  
768 Panel Reports, para.  7.704.  
769 Panel Reports, para.  7.707.  
770 Panel Reports, para.  7.717.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.1.6   Conclusion under Article  2.1 of the TBT  Agreement  
6.258.   Based on our analyses and findings in  sections 6.1.1 to 6.1.5 above , we uphold  the 
Panels'  conclusion that the 2016 Tuna Measure accords to Mexican tuna products treatment no less 
favourable than that accorded to like products from the United  States and other countries and 
therefore is consistent with Article  2.1 of the TBT  Agreement.771 
6.2  Article  XX of the GATT  1994  
6.259.   At the outset of their analysis, and noting the part ies' agreement in this regard, the Panels 
found that the 2016 Tuna Measure is inconsistent with Articles  I:1 and  III:4 of the GATT  1994772, 
but is provisionally justified under subparagraph (g) of Article  XX of the GATT 1994 .773 The Panels 
hence focused their analysis on the disagreement between the  parties as to whether the 
2016 Tuna Measure meets the requirement of the chapeau  of Article  XX, and concluded:  
[H]aving found, in our analysis under Article  2.1 of the TBT Agreement , that the 
Measure is calibrated to different levels of risks posed to dolphins by different fishing 
methods in different areas of the ocean, we also find that the Measure is not applied in 
a manner that constitutes a means of arbitrary or unjustifiable disc rimination, and is 
therefore justified under Article  XX of the GATT  1994.774 
6.260.   Mexico appeals the above conclusion, arguing that the Panels erred in relying on their 
reasoning developed under Article  2.1 of the TBT Agreement , and thereby failed to consider whe ther 
the discrimination caused by the measure is rationally related to its objectives as required by the 
applicable legal standard under the chapeau  of Article  XX of the GATT  1994.775 We begin by recalling 
the relevant findings by the Panels, before analysing the issues raised by Mexico's appeal.  
6.2.1   The Panels' findings  
6.261.   The Panels recalled that three analytical elements must be demonstrated with respect to  
arbitrary or unjustifiable discr imination under the chapeau  of Article  XX, namely: (i)  the application 
of the measure results in discrimination; (ii)  the conditions prevailing between countries are the 
same; and (iii)  the discrimination is arbitrary or unjustifiable.776 With respect to the  existence of 
discrimination, the Panels noted the Appellate  Body's finding in the first compliance proceedings 
that, by excluding most Mexican tuna products from acc ess to the "dolphin -safe" label  while granting 
conditional access to such label to like  products from the United  States  and other countries, the 
2013 Tuna Measure, similar to the original  Tuna Measure, modified the conditions of competition to 
the detriment of Mexican  tuna products in the US  market.777 Since the 2016  Tuna Measure maintains 
the ov erall architecture and structure of the original and 2013  Tuna Measures, the Panels found that 
"the 2016 Tuna Measure continues to cause the same detrimental impact resulting from the 
discriminatory treatment between tuna products containing tuna caught in  the ETP large purse  seine 
fishery and those containing tuna caught in other fisheries. "778  
6.262.   With respect to the second  element, the Panels recalled that , in the first compliance 
proceedings, the Appellate  Body found that , in this dispute,  the conditions pre vailing between 
countries are the same for the purpose of the chapeau  of Article  XX, namely, "the risks of adverse 
                                                
771 Panel Reports, paras.  7.717, 8.2, and 8.6.  
772 Panel Reports, para.  7.729 (refer ring to First Compliance Panel Report, paras.  7.404 -7.416, 7.434, 
7.469 -7.481, and 7.494 -7.495; Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , 
para. 8.1(d)(ii)).  
773 Panel Reports, para.  7.730 (referring to First Compliance Panel Repor t, para.  7.541; Appellate  Body 
Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.341).  
774 Panel Reports, para.  7.740.  
775 Mexico's Notice of Appeal, para. 10; appellant's submission, paras. 308 -309. 
776 Panel Reports, para.  7.731.  
777 Panel Reports, para.  7.732 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.238).  
778 Panel Reports, para.  7.732.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  effects on dolphins arising from tuna fishing practices".779 The Panels noted that, with regard to the 
first two elements, neither of the parties had argued otherwise before them.780  
6.263.   With respect to the third element, that is, whether the measure is applied in a manner that 
constitutes a means of "arbitrary or unjus tifiable discrimination", the Panels found that, based on 
the guidance provided by the Appellate  Body in the first compliance proceedings, "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".781 The Panels 
then recalled that, following the guidance provided by the Appellate  Body in the first compliance 
proceedings, they had conducted their analysis under Article  2.1 "on the basis of the concept of 
calibration, and found that the 2016 Tuna Measure is calibrated to different risks to dolphins arising 
from the use of different fishing m ethods in different areas of the ocean ".782 On this basis, the Panels 
recalled that they had concluded that the detrimental impact caused by the 2016  Tuna Measure 
"stems exclusively from legitimate regulatory distinctions, and that, therefore, the Measure is  
consistent with Article  2.1 of the TBT Agreement ".783  
6.264.   The Panels found that, in the circumstances of the present compliance proceedings, and in 
light of the Appellate  Body's guidance in the first compliance proceedings, it was appropriate to use 
their fact ual and legal findings under Article  2.1 in their assessment of whether the 2016 Tuna 
Measure is applied in a manner that constitutes arbitrary or unjustifiable discrimination within the 
meaning of the chapeau  of Article  XX.784 In this regard, the Panels  did not consider that the 
2016 Tuna Measure, "which is tailored to and commensurate with the relevant risks, can be said to 
applied in a manner that constitutes a means of 'arbitrary or unjustifiable discrimination'"  within the 
meaning of Article XX of the GA TT 1994 .785 Therefore, in light of their finding under Article  2.1, the 
Panels concluded that the 2016 Tuna Measure is not applied in a manner that constitutes a means 
of arbitrary or unjustifiable  discrimination within the meaning of the chapeau  and is ther efore 
justified under Article  XX of the GATT  1994.786 
6.2.2   Whether the Panels erred in finding that the 2016 Tuna Measure complies with the 
requirements of the chapeau  of Article  XX of the GATT  1994  
6.265.   Mexico claims on appeal that the Panels erred in relying on their analysis under Article  2.1 
to conclude  that the 2016 Tuna Measure is not inconsistent with the requirements of the chapeau of 
Article  XX. Mexico submits that, to examine whether a measure is  applied in a manner that 
constitutes arbitrary or unjustifiable discrimination under the chapeau , a panel must consider 
"whether the detrimental impact caused by the measure can be reconciled with, or rationally 
connect ed to, the policy objective  … that w as provisionally found to justify the measure" under one 
of the subparagraphs of Article  XX.787 Mexico contends that the Panels made no substantive findings, 
under Article  2.1, with respect to arbitrary or unjustifiable discrimination . Thus, according to Mex ico, 
by relying on their analysis under Article  2.1 for the purpose of the chapeau  of Article  XX, the Panels 
did not properly take into account the differences between the legal analyses required under these 
provisions.788  
6.266.   Mexico recalls the Appellate  Body's finding in the first compliance proceedings that, if the 
similarities and differences between Article  2.1 and Article  XX are taken into account, it may be 
                                                
779 Panel Reports, para.  7.733 (referring to Appellate  Body Report, US – Tuna II (Mexico)  
(Article  21.5 – Mexico) , para.  7.308).  
780 Panel Reports, paras.  7.732 -7.733 (referring to Mexico's first written submission to the Panels, 
para. 204; response to Panel question No. 110; United States' first written submission to the Panels, para. 69; 
response to Pane l question No. 110).  
781 Panel Reports, paras. 7.727 and  7.734 (quoting Appellate  Body Report, US – Tuna II (Mexico) 
(Article  21.5 – Mexico) , para.  7.347).  
782 Panel Reports, para.  7.738. In the Panels' view, they did not repeat the first compliance panel's 
errors found by the Appellate  Body, namely, the first compliance panel's segmented analysis under Article  2.1 
of the TBT  Agreement and its erroneous assumpti on that disqualifying tuna products containing tuna caught by 
setting on dolphins from accessing the label was consistent with that provision. (Ibid., paras.  7.735 -7.736)  
783 Panel Reports, para.  7.738.  
784 Panel Reports, para.  7.739.  
785 Panel Reports, para.  7.739. 
786 Panel Reports, para.  7.740.  
787 Mexico's appellant's submission, para.  309. 
788 Mexico's appellant's submission, para.  315. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  permissible to rely on reasoning developed under one provision for the analysis under the other.789 
Mexico highlights that, in the first compliance proceedings, the panel conducted its analyses under 
Article  2.1 and Article  XX on the basis of the same legal test, that is, whether the measure at issue 
was designed and applied in a manner that constitutes a rbitrary or unjustifiable discrimination .790 
In Mexico's view, due to the Panels' failure to examine the rational relationship between the 
regulatory distinctions of the 2016 Tuna Measure and its objectives under Article  2.1, the 
Panels'  findings under Article 2.1 could not be used to resolve the assessment of arbitrary or 
unjustifiable discrimination under Article XX .791  
6.267.   The United  States  argues that the Panels did not err in relying on their findings under 
Article  2.1 for their analysis under the chapea u of Article  XX. The United  States  submits that, as the 
Appellate  Body indicated in the first compliance proceedings, the analysis of whether the 
requirements under the 2016 Tuna M easure are calibrated to the risks to dolphins posed by tuna 
fishing is "rel evant for an analysis of arbitrary or unjustifiable discrimination under the chapeau of 
Article  XX".792 Moreover, the United  States  recalls that the Appellate  Body reversed the first 
compliance panel's analyse s under both Article  2.1 and Article  XX for ident ical reasons, namely, 
because the panel had conducted a segmented analysis that  failed to assess whether the measure, 
as a whole, was calibrated to the risk s to dolphins posed by different fishing methods in different 
ocean areas.793 Given that the Panels co nducted a proper calibration analysis under Article  2.1, the 
United  States  contends that the differences between the Panels' assessment and the first  compliance 
panel's assessment only "confirm that the Panels did not err in relying on their analysis and 
conclusions under Article  2.1".794  
6.268.   The United  States  further contends that, contrary to Mexico's arguments, the Panels' 
analysis under Article  2.1 encompassed an assessment of whether the regulatory distinctions of the 
2016 Tuna Measure were rationally relat ed to the objectives of the measure. This is because the 
Panels explained that the objectives of the measure inform both the form and the content of the 
calibration analysis, and thus the rational relation ship test does not exist as a separate legal step, 
but rather is assessed through the calibration analysis itself.795 The United  States  adds that the 
Appellate  Body's analysis in the two  previous proceedings confirms that the calibration assessment, 
"done correctly, … reflects the relationship between the distinctions of the measure and the 
measure's objective that renders the measure not discriminatory".796 
6.269.   The participants' disagreement on appeal centres  on whether it was permissible for the 
Panels, in the circumstances of these compliance proceedings, to r ely on their calibration analysis 
under Article  2.1 in reaching their conclusion that the 2016  Tuna Measure is not applied in a manner 
that constitutes arbitrary or unjustifiable discrimination within the meaning of the chapeau  of 
Article  XX. The chapeau  of Article  XX provides, in relevant part , that : 
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 
                                                
789 Mexico's appellant's submission, para.  317 (referring to Appellate  Body Report, US – Tuna II 
(Mexico) (Article  21.5 – Mexico) , paras.  7.345 -7.347).  
790 Mexico's appellant's submission, para. 318.  
791 Mexico's appellant's submission, paras.  319-330 (referring to Appellate  Body Report, US – Tuna II 
(Mexico) (Article  21.5 – Mexico) , para. 7.320). Mexico also argued in its appellant's sub mission that the 
2016 Tuna Measure results in "unjustifiable discrimination" because the United  States did not seek a 
multilateral solution before imposing a unilateral measure. Mexico referred in this regard to the Appellate  Body 
Report in US – Shrimp , and argued that of importance in the present proceedings is the fact that there is a 
fully functioning and highly effective multilateral process already in place that the United  States helped to 
create in the form of the IATTC and its dolphin -protection prog ram, which the United  States chose to ignore. 
(Ibid., paras.  333-334) However, during the hearing, Mexico indicated that it was not pursuing a decision by 
the Appellate  Body on this issue but merely included it in its appellant's submission as relevant bac kground. 
(Mexico's response to questioning at the hearing) Therefore, we do not address this claim.  
792 United  States' appellee's submission, para.  365 (quoting Appellate  Body Report, US – Tuna II 
(Mexico) (Article  21.5 – Mexico) , para. 7.330).  
793 United  States' appellee's submission, para.  367 (referring to Appellate  Body Report, US – Tuna II 
(Mexico) (Article  21.5 – Mexico) , paras.  7.229 and 7.334 -7.335).  
794 United  States' appellee's submission, para.  367. 
795 United  States' appellee's submission, para.  368 (re ferring to Panel Reports, paras.  7.115 -7.127).  
796 United  States' appellee's submission, para.  370. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the same conditions prevail … nothi ng in this Agreement shall be construed to prevent 
the adoption or enforcement by any contracting party of measures . 
6.270.   By its terms, the chapeau  of Article  XX is concerned with the "manner" in which a measure 
that falls under one of the subparagraphs of Article XX is "applied".797 The Appellate  Body has noted 
that the manner in which a measure is applied  "can most often be discerned from [its] 
design,  … and … revealing structure".798 The Appellate  Body has explained that there are three 
constitutive elements in a ssessing the requirement s under the chapeau : (i) the application of the 
measure must result in discrimination; (ii)  the discrimination must occur between countries where 
the same conditions prevail; and (iii)  the discrimination must be arbitrary or unjusti fiable in 
character.799  
6.271.   The Appellate  Body has found 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'."800 Such analysis "'shoul d be made in the light of the  objective of the measure', 
and … 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'" .801 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 which the m easure has been provisionally justified under one of the 
subparagraphs of Article  XX."802  
6.272.   The Appellate  Body has further found that there are important parallels between the 
analyses under the chapeau  of Article  XX and Article  2.1. In particular, the Appell ate Body has noted 
that the concept of "arbitrary or unjustifiable discrimination between countries where the same 
conditions prevail" is found both in the chapeau  of Article  XX and in the sixth recital of the preamble 
of the TBT Agreement , which the Appel late Body has found to provide relevant context for the 
interpretation of Article  2.1.803 At the same time, the Appellate  Body has cautioned that there are 
also differences between these provisions , inter alia, in terms of their legal standards804, as well as 
their main function and scope. In particular, the Appellate  Body has noted that, while the analysis 
under Article  2.1 concerns the regulatory distinction that accounts for the detrimental impact on 
imported products, the discrimination examined under the chapeau  of Article  XX is not necessarily 
the same as the discrimination found to be inconsistent with the relevant provisions of the 
GATT  1994, "such as Articles I and III ".805 
6.273.   In the first compliance proceedings, the Appellate  Body stated that, "so long as t he 
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 und er the other."806 The 
Appellate  Body noted that the first compliance panel had conducted its analyses under both 
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 
                                                
797 See also Appellate  Body Reports, US – Gasoline , p. 22, DSR 1996:I, p. 20; US – Shrimp , para.  115; 
Brazil  – Retreaded Tyres , para.  215. 
798 Appellate  Body Repo rt, Japan – Alcoholic Beverages II , p. 29, DSR 1996:I, p. 120.  
799 Appellate  Body Report, US – Shrimp , para.  150. 
800 Appellate  Body Report, Brazil – Retreaded Tyres , para.  226. 
801 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.316 (quoting 
Appellate  Body Report, Brazil – Retreaded Tyres , para.  227).  
802 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.316 (quoting 
Appellate  Body Reports, EC – Seal Products , para.  5.306). The Appellate  Body has also e xplained 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, additional factors may also be relevant to the overall assessment. (Ibid. (referring to Appellate  Body 
Reports, EC – Seal Products , para.  5.321))  
803 Appellate  Body Reports, US – Clove Cigarettes , para.  173; US – Tuna II (Mexico) , para.  213;  
EC – Seal Products , para.  5.310.  
804 Specifically, Article  2.1 of the TBT  Agreement requires panels to consider whether the detrime ntal 
impact on imported products caused by a measure stems from a legitimate regulatory distinction. 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 unjust ifiable discrimination between countries where the same conditions 
prevail. (See Appellate  Body Reports, EC – Seal Products , para.  5.311)  
805 Appellate  Body Reports, EC – Seal Products , para.  5.312.  
806 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.347.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  rationally related to, the policy objective with respect to which the measure has been provisionally 
justified ".807 In these circumstances, the Appellate  Body considered that it was appropriate for th e 
first compliance panel, "in principle, to have referred to and relied on" the reasoning it had developed 
in the context of Article  2.1 in its analysis under the chapeau  of Article  XX.808 
6.274.   The Appellate  Body emphasized that, in th e circumstances of this disp ute, "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" was "relevant  for an analysis of a rbitrary or unjustifiable discrimination under the 
chapeau of Article  XX".809 This was because the first  compliance panel was required to examine the 
United  States ' claim that "any differences in the regulatory requirements of the [2013 Tuna Measure] 
are jus tified by reference to the objective of dolphin protection because such differences reflect the 
differences in risks" to dolphins arising from the use of different fishing methods in different ocean 
areas.810 However, the Appellate  Body recalled its criticis m of the first compliance panel's  findings 
under Article  2.1, including that the first compliance panel had failed to conduct a proper calibration 
analysis, and that  the first compliance panel's "decision to adopt a segmented analytical approach 
prevented it from properly applying the legal standard that it had articulated"811, namely, "whether 
the detrimental treatment can be reconciled with, or is rationally related to, the policy pursued by 
the measure at issue".812 In the Appellate  Body's view, "these criticisms concern aspects of the [first 
compliance panel's] reasoning and findings that it also relied upon in the context of its analysis under 
the chapeau of Article  XX" of the GATT  1994.813 In light of these errors814, the Appellate  Body 
reversed the first compliance panel's finding s under the chapeau  of Article  XX.815 
6.275.   The above findings indicate that, in the circumstances of this dispute, it was appropriate for 
the first compliance panel to "rel[y] on a similar analytica l process under" both Article  2.1 and the 
chapeau  of Article  XX.816 This process sho uld have involved ascertaining the existence of arbitrary 
or unjustifiable discrimination through an examination of whether such discrimination can be 
reconciled with, or is rationally related to, the measure's policy objective .817 Furthermore, for t his 
analytical process, it was relevant to examine whether the regulatory distinctions under the measure 
at issue were calibrated to different risks to dolphins arising from the use of different fishing methods 
in different areas of the ocean.818 However, because the first compliance panel had failed to conduct 
a proper calibration analysis under Article  2.1, and had adopted a segmented approach to analysing 
the requirements under the m easure, the panel had also failed to examine properly the rational 
relationship between the measure's objectives and the regulatory distinctions giving rise to the 
discrimination. As a result, the first compliance panel's findings under Article  2.1 had not  in fact 
ascertain ed the existence of arbitrary or unjustifiable discrimination. Thus, by relying on the same 
reasoning and analysis developed under Article  2.1, the errors committed by the first compliance 
                                                
807 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.347.  
808 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.320.  
809 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.330. (emphasis added)  
810 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.330.  
811 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.332.  
812 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.229 (quoting First 
Compliance Panel Report, para. 7.91).  
813 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.332.  
814 In addition to the above -mentioned errors, the Appellate Body also con sidered that the first 
compliance panel had failed to properly analyse whether the existing discrimination is between countries where 
the same conditions prevail. (Appellate Body Report, US – Tuna II (Mexico) (Article 21.5 – Mexico) , 
para. 7.333) As noted above, this issue is not in dispute in the present proceedings. (See paras. 6.261 -6.262 
above)  
815 Appellate Body Report, US – Tuna II (Mexico) (Article 21.5 – Mexico) , paras.  7.333 -7.335. At the 
same time, the Appellate  Body recalled that, in completing the  analysis in the context of its findings under 
Article  2.1 of the TBT  Agreement, it had examined other features of the Tuna Measure that were not dependent 
on the first compliance panel's calibration analysis. In this regard, the Appellate  Body agreed with  the panel 
that the determination provisions left a "gap" in that fisheries other than the ETP large purse seine fishery may 
be treated differently, and less stringently, even where the conditions in that fishery mirror those in the 
ETP large purse seine f ishery. (Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , 
paras.  7.354 -7.359) Therefore, the Appellate  Body found that, with respect to the determination provisions, 
the United  States had not demonstrated that the 2013 Tuna Measure was  applied in a manner that did not 
constitute arbitrary or unjustifiable discrimination. Consequently, the Appellate Body found that the 2013 Tuna 
Measure was not justified under Article  XX of the GATT  1994. (Ibid., para.  7.359)  
816 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.320.  
817 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , paras.  7.320 and  7.347.  
818 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.330.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  panel therein also undermined its finding regardi ng arbitrary or unjustifiable discrimination under 
the chapeau  of Article  XX. 
6.276.   Turning to Mexico's appeal in these compliance proceedings, we recall that its claim under 
the chapeau of Article  XX is premised on its view that the calibration analysis conduct ed by the 
Panels under Article 2.1 of the TBT Agreement did not encompass consideration of the rational 
relationship between the regulatory distinctions of the 2016 Tuna Measure and its objectives.819 
According to Mexico, because an assessment of such a relationship is required for examining 
arbitrary or unjustifiable discrimination under the chapeau  of Article  XX, the Panels erred by relying 
on their findings , made under Article  2.1, for their analysis under the chapeau  of Article  XX.820  
6.277.   We recall that , in this dispute,  the "discrimination between countries where the same 
conditions prevail" for the purpose of the chapeau  of Article  XX ar ises from the fact that "the 
2016 Tuna Measure continues to cause the same detrimental impact resulting from the 
discrimin atory treatment between tuna products containing tuna caught in the ETP large purse -seine 
fishery and those containing tuna caught in other fisheries ."821 Thus, while  the discrimination 
examined under the chapeau of Article  XX may not be the same as the disc rimination found to be 
inconsistent with the relevant provisions of the GATT  1994, in the present dispute , the relevant 
discrimination for the analysis under the chapeau  of Article  XX is the same as the detrimental impact 
caused by the relevant regulatory distinctions examined by the Panels in the context of Article  2.1. 
Furthermore, we recall that two elements of the legal test under the chapeau  – namely, the existence 
of discrimination  between countries , and whether the same conditions prevail in those  
countries  – are not at issue between the parti es.822 This means that the issue before us concerns , 
exclusively , whether the 2016 Tuna M easure is applied in a manner that constitute s a means of 
arbitrary or unjustifiable discrimination.  
6.278.   In this regard, we recall  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."823 As discussed  in 
section  6.1.3.1  above, considerations of the rational relationship between the regulatory distinctions 
causing  such detrimental impact and the obje ctives of the 2016 Tuna Measure, rather than being a 
separate inquiry, are encompassed in  a proper calibration analysis under Article  2.1. This is because, 
where the calibration analysis  is conducted properly , it would  also ascertain whether the label 
granted under the measure at issue convey s the information regarding the dolphin -safe nature of 
the tuna products to consumers. Thus, as explained, we consider that a proper assessment of 
whether the measure is calibrated to the risks to dolphins arising from the use of different fishing 
methods in different areas of the ocean would take into account the objectives of the 2016 Tuna 
Measure regarding dolphin protection and consumer information .824 Such an assessment would  also 
help to ascertain the nexus between such objectives and the regulatory distinctions  drawn under the 
measure.  
6.279.   Furthermore, in section s 6.1.4 and 6.1.5 above , we have found that t he Panels conducted a 
proper calibration analysis of the 2016 Tuna Measur e by assessing whether the regulatory 
distinctions of the 2016 Tuna Measure are calibrated to  different risks to dolphins arising from the 
use of different fishing methods in different areas of the ocean. We consider that the 
Panels'  sequential analyses of  each of the elements of the 2016  Tuna Measure, as well as their 
examination of the measure as a whole, were properly informed by the interlinkages between these 
elements and the fact that they operate together to regulate access to the dolphin -safe label.825 
We thus agree with the Panels that they were "mindful" of the Appellate  Body's guidance in the 
previous compliance proceedings, and that they conducted their calibration analysis accordingly.826 
In our view, unlike the first  compliance panel's assessment o f the  2013 Tuna Measure, the 
Panels'  calibration analysis under Article  2.1 encompassed consideration of the rational relationship 
                                                
819 Mexico's appella nt's submission, para.  319. 
820 Mexico's appellant's submission, para.  315. 
821 Panel Reports, para.  7.732.  
822 See paras. 6.261 -6.262 above.  
823 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.316 (quoting 
Appellate  Body Reports, EC – Seal Products , para.  5.306).  
824 Panel Reports, para.  7.125.  
825 See paras. 6.256 -6.257 above.  
826 Panel Reports, paras.  7.736 -7.737.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  between the regulatory distinctions of the 2016 Tuna Measure and its objectives. Th us, the 
Panels'  analysis  under Article  2.1 also demonstrate s that the 2016 Tuna Measure is not designed or 
applied in a manner that constitutes arbitrary or unjustifiable discrimination within the meaning of 
the chapeau  of Article  XX.  
6.280.   In sum, the calibration analysis is the tool in the circumstan ces of this dispute to assess 
whether the 2016  Tuna Measure is consistent with Article  2.1. It follows that, if the 
2016 Tuna Measure is properly  calibrated and hence not inconsistent with Article  2.1, it will also not 
be found to be applied in a manner th at constitutes arbitrary or unjustifiable discrimination. 
Furthermore, given the "important parallel s" between the analyses under Article  2.1 and the 
chapeau  of Article  XX discussed above, the 2016 Tuna Measure, which  is not applied in a manner 
that amount s to arbitrary or unjustifiable discrimination under the former , would  also be found not 
to amount to such discrimination under the latter. Hence , in the circumstances of this dispute, a 
proper calibration analysis is a tool that also serves to determine w hether the measure is applied in 
a manner that does not constitute arbitrary or unjustifiable discrimination for the purpose of the 
chapeau  of Article  XX.  
6.281.   In light of the above considerations, we share the Panels' view that, because "the 2016 Tuna 
Measure  is 'tailored to', and 'commensurate with', the different risks to dolphins caused by different 
fishing methods in different parts of the ocean", this also demonstrates that the discrimination under 
the measure "can[not] be said to be applied in a manner t hat constitutes a means of 'arbitrary or 
unjustifiable discrimination' within the meaning of Article  XX".827 Therefore , we disagree with Mexico 
that the Panels "declin[ed] to conduct, either under Article  2.1 or the chapeau  of Article  XX, a full 
assessment of whether the [2016 Tuna Measure] is designed or applied in a manner that constitutes 
arbitrary or unjustifiable discrimination".828  
6.282.   Mexico additionally contends that there is "an apparent conflict" in the Panels' reasoning.829 
This is because, on the one ha nd, the 2016 Tuna Measure is provisionally justified as relating to 
"conservation of exhaustible natural resources" under Article  XX(g).830 On the other hand , according 
to Mexico, the Panels "refus[ed] to consider", in their calibration analysis under Article 2.1, "PBR  data 
and evidence demonstrating that certain fishing methods in certain areas of the oceans are causing 
adverse effects that threaten the collapse of dolphin populations".831 Mexico argues   
that t he Panels' calibration analysis focuses on the ris ks to indiv idual dolphins and 
"overlook[s]  … mortalities that do endanger the population of dolphins in [three longline] 
fisheries".832 Thus, to Mexico, by relying on their erroneous calibration analysis for the purpose of 
the chapeau  of Article  XX, the Panels failed to properly examine whether the discrimination under 
the 2016 Tuna M easure can be reconciled with, or is rationally related to, the policy objective of 
conserving exhaustible natural resources, with respect to which the measure has be en provisionally 
justified under Article XX (g).833 In Mexico's view, this conflict in the Panels' reasoning shows that 
their refusal to consider "PBR data and evidence demonstrating that certain fishing methods in 
certain areas of the oceans are causing adve rse effects that threaten the collapse of dolphin 
populations is not objective and is legally incorrect".834 
6.283.   We recall that, in the first compliance proceedings, the Appellate  Body rejected Mexico's 
argument that the panel erred in articulating the legal sta ndard under the chapeau of Article XX as 
consisting of a focus on whether there is a rational connection with the objectives of the 2013 Tuna 
Measure, rather than the objective reflected in Article  XX(g).835 The Appellate  Body considered such 
a distinction t o be "somewhat artificial" given that, "by virtue of an examination of whether a 
measure is provisionally justified under one of the subparagraphs, the objective of the measure will 
                                                
827 Panel Reports, para.  7.739.  
828 Mexico's appellant's submission, para.  315. 
829 Mexico's appellant's submission, para.  316. 
830 Mexico's appellant's submission, para.  316. 
831 Mexico's appellant's submission, para.  316. 
832 Mexico's appellant's submission, para.  215. (emphasis omitted) We recall that PBR evidence 
calculates the "maximum possible number of animals … which can be remove d from an animal stock without 
affecting the population or its sustainability". (Panel Reports, para.  7.184) These three fisheries are the Main 
Hawaii Island Insular Stock Longline fishery, the West North Atlantic Longline fishery, and the Pelagic Hawaii 
Longline fishery. (Mexico's appellant's submission, para. 215. See also Panel Reports, para.  7.473)  
833 Mexico's responses to questioning during the hearing.  
834 Mexico's appellant's submission, para.  316. 
835 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.318.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  already have been tested against, and will have been found to be aligned w ith, one of the objectives 
set out in Article  XX."836 The Appellate  Body did not understand how, in the circumstances of th is 
dispute, where the first compliance panel found that the objective of dolphin protection relates to 
the conservation of exhaustible natural resources, "reliance on the objective of Article  XX(g), rather 
than that of the measure, would yield a different analytical result ".837 
6.284.   We consider that Mexico's argument in the present compliance proceedings introduces a  
similar  artificial distinction between the objective of the 2016 Tuna Measure of protecting individual 
dolphins and the objective of "conservation of exhaustible natural resources" within the meaning of 
Article  XX(g). In  section 6.1.4.4  above, we reviewed Mexico' s argument that the Panels erred in not 
relying on PBR evidence for assessing the risks to dolphins arising from the use of different fishing 
methods in different ocean areas. We agreed with the Panels' assessment that the PBR methodology 
prioritizes the s ustainability of the population in a way that would have prevented the Panels from 
adequately assessing whether the measure is calibrated to different risks that a dolphin was killed 
or seriously injured in the fishing process .838 That said, the fact that th e Panels sought to examine 
whether the measure is calibrated to risks to individual dolphins does not mean that their calibration 
analysis failed to take into account the rational connection between the regulatory distinctions giving 
rise to the discrimina tion and the goal of conserv ing exhaustible natural resources.  
6.285.   We also recall that the Panels noted  the original and first compliance panel's findings  that 
the Tuna Measure is "more concerned with the 'well -being of individual dolphins'"839, and the 
dolphin -protection objective thereof is not to "be understood exclusively, or even primarily, in terms 
of dolphin population recovery ".840 The Panels further  noted that addressing adverse effects to 
individual dolphins "might also be considered as seeking to conser ve dolphin populations" and that, 
consequently, the  objectives of the measure "also incorporate" considerations regarding 
conservation.841 The Panels highlighted that "mortality or serious injury suffered by individual 
dolphins may also have population -level consequences ."842 We further recall that, as the first 
compliance panel  found , "the preservation of individual dolphin lives is just as much an act of 
conservation as is a program to encourage recovery of a particular population", and that "there is 
an essential and inextricable link between the protection of dolphins on an individual scale and the 
'replenishment of [an] endangered species', for it is only through protecting individual dolphins that 
a population itself can be protected, replenished, and maintained."843  
6.286.   We therefore disagree with Mexico's assertion that, because tuna harvested in three fisheries 
with low PBR levels may be  eligible to receive "dolphin -safe" labels under the 2016 Tuna Measure, 
the measure is "not concerned" with the risks rel ated to fishing methods that threaten the 
sustainability of dolphin populations.844 As explained above, findings by the original and first 
compliance panels, as well as the present Panels, indicate that, w hile the 2016  Tuna Measure may, 
first and foremost, b e "concerned" with the protection of individual dolphins, the measure also  
protects dolphin populations by ensuring that tuna  producers who seek to have access to the 
"dolphin -safe" label are deterred from harvesting tuna in a manner that harms dolphins.845 
Therefore, the fact that the 2016 Tuna Measure does not disqualify tuna caught in the three fisheries 
concerned from accessing the dolphin -safe label does not mean that it fails to address the 
conservation of dolphin populations. Rather, by seeking to ensu re that individual dolphins are not 
being harmed in the fishing process , the 2016 Tuna M easure is also related to  the conservation of 
these populations.  
                                                
836 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.318.  
837 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.318.  
838 See paras. 6.130 -6.131 above.  
839 Panel Reports, fn  331 to para.  7.187 (referring to Original Panel Report, para.  7.596; quoting 
First Compliance Panel Report, para.  7.527).  
840 Panel Reports, para.  7.187 (quoting Original Panel Report, paras.  7.550 and  7.735).  
841 Panel Reports, fn  331 to pa ra. 7.187 (referring to Original Panel Report, para.  7.596; 
First Compliance Panel Report, para.  7.527).  
842 Panel Reports, para.  7.186.  
843 First Compliance Panel Report, para.  7.527. The first compliance panel also indicated that "the fact 
that the [2013 Tun a Measure] is more concerned with the effects of tuna fishing on the well -being of individual 
dolphins rather than on the state of a particular dolphin population, considered globally or statistically, does 
not in itself negate the nexus between the measur e and the goal of conserving exhaustible natural resources." 
(Ibid.) Mexico did not appeal these findings in the first compliance proceedings.  
844 Mexico's appellant's submission, para.  316. 
845 Panel Reports, para. 7.186.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.287.   In any event, b y acknowledging that the 2016  Tuna Measure is provisionally justified under 
Article  XX(g) of the GATT  1994, Mexico accepted that the measure and its objectives, including the 
protection of individual dolphins, are "designed" to address, and are "related to", the "conservation 
of exhaustible natural resources".846 Therefore, given that the regul atory distinctions causing the 
discrimination under the 2016  Tuna Measure are rationally related to the protection of individual 
dolphins, we do not consider that this discrimination "bears no rational connection to", or wou ld 
"go against", the objective o f "conservation of exhaustible natural resources".847 As the 
Appellate  Body found in the first compliance proceedings, once the measure  at issue in this dispute  
is found to be provisionally justified under Article  XX(g), whether the rational relationship 
requirement under the chapeau  of Article  XX is analysed through the lens of the objectives pursued 
by the measure, or the policy objectives contained in Article  XX(g), the analysis  should not yield a 
different result.848 In light of this finding, and the considerations set out above, we disagree with 
Mexico's contention that, because of the Panels' rejection of the PBR evidence, their calibration 
analysis cannot support a finding that the regulatory distinctions giving ri se to the discrimination 
under the 2016 Tuna Measure are rationally related to the conservation of exhaustible natural 
resources.  
6.2.3   Conclusion  
6.288.   In sum, one of the most important factors in the assessment of arbitrary or unjustifiable 
discrimination under the chapeau of Article  XX of the GATT  1994 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. 
As indicated above, the Appellate  Body's guidance in the first compliance proceedings indicates that 
the calibration analysis is the tool in the circumstances of this dispute to assess whether the 
2016 Tuna Measure is consistent with Article 2.1 of the TBT Agreement . If done  properly , the 
calibration  analysis would  encompass consideration of the rational relationship between the 
regulatory distinction of the 2016  Tuna Measure and its objectives. As also indicated, it was 
appropriate for the Panels, in the circumstances of these compliance proceedings, to rely on their 
calibration analysis under Article  2.1 in their assessment of whether the 2016  Tuna Measure is 
applied in a manner that constitutes arbitrary or unjustifiable discrimination wit hin the meaning of 
the chapeau  of Article  XX. This is because, where  the differences between Article  2.1 and Article  XX 
are taken into account, it may be permissible to rely on reasoning developed in the context of one 
agreement for the purpose of  conducti ng an analysis under the other.  
6.289.   We also indicated in  section 6.1.5 above that the Panels did not err in finding that the 
2016 Tuna Measure is calibrated  to the risks to dolphins arising from the use of different fishing 
methods in different areas of the ocean. Therefore, given that consideration of the rational 
relationship between the regulatory distinctions and the objectives of the 2016  Tuna Measure was 
encompassed in this analysis , we find that the P anels did not err in relying on the reasoning 
developed under Article  2.1 of the TBT Agreement  in assessing the conformity of the 2016 Tuna 
Measure with the chapeau  of Article  XX of the GATT  1994. We also reject Mexico's contention that, 
due to the  Panels'  reliance on per set  evidence , rather than PBR evidence , in assessing the risks to 
dolphins, the ir calibrat ion analysis cannot be relied on for assessing whether the 2016 Tuna Measure 
is rationally related to the conservation of exhaustible natural resourc es. 
                                                
846 The Appellate  Body has found that t he provisional justification of a measure under one of the 
exceptions requires, first, that the measure be designed  to "address the particular interest specified in that 
paragraph" and, second, that "there be a sufficient nexus between the measure and the interest protected". 
(Appellate Body Report, US – Gambling , para. 292. See also Appellate Body Reports, EC – Seal Products , 
para. 5.169 and fn 1178 thereto) The required nexus is specified in the language of the paragraphs themselves 
through the use of ter ms such as "necessary to", "essential to", or – as in the case of Article  XX(g), which is 
relevant to the present dispute – "relating to". (Appellate  Body Report, Colombia – Textiles , para.  5.67 
(referring to Appellate Body Report, US – Gambling , para. 292)) We also observe that the United  States agree 
with Mexico that the 2016 Tuna Measure is provisionally justified under Article  XX(g). (Panel Reports, 
para. 7.730) The issue of the provisional justification of the 2016 Tuna Measure is not on appeal befo re us.  
847 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.316 (quoting 
Appellate  Body Report, Brazil – Retreaded Tyres , para.  227).  
848 Appellate  Body Report, US – Tuna II (Mexico) (Article  21.5 – Mexico) , para.  7.318.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.290.   For the foregoing reasons , we uphold  the Panels' finding that the 2016 Tuna Measure is not 
applied in a manner that constitutes a means of arbitrary or unjustifiable discrimination and is 
therefore justified under Article  XX of the GATT  1994.849 
6.3  The Panels' decision to hold a partially open meeting  
6.291.   Mexico appeals " the findings and conclusion of the Panels that they had the authority to 
conduct a partially open meeting of the parties without the consent of both Parties" .850 In response, 
the United  States  contends that Mexico's appeal is not properly raised due to deficiencies in Mexico's 
Notice of Appeal in light of Article  17.6 of the DSU and Rule  20(2)(d) of the Working Procedures for 
Appellate Review (Working  Procedures ).851 
6.3.1   Procedural background  
6.292.   At the organizational meetings of the Panels in these proceedings, held on 10  June 2016 and 
14 July 2016, respectively, the United  States  proposed a change to the Panels' working procedures 
to allow the Panels' substantive meeting to be publicly observed. Alterna tively, if Mexico did not 
agree to this, the United  States  requested the Panels to allow a party to request a partially open 
meeting, whereby that party's statements during the Panel's meeting with the parties could be 
viewed by the public, either simultan eously or through a delayed broadcast. The statements of a 
party that wished to maintain the confidentiality of these statements could not be so viewed.852 
Mexico opposed the United  States ' request that the  Panels conduct an open meeting  either fully or 
partially. Mexico argued that the Panels could only open their substantive meetings with the parties 
to public viewing with the consent of both parties.853 
6.293.   On 4 July 2016, the Panel in the proceedings brought by the United  States  sought the views 
of the third pa rties on this procedural issue. Nine third parties provided their views. 
Six third parties854 opposed the United  States ' request, whereas three855 did not.856 
6.294.   On 29  July 2016, the Panels informed the parties that they considered themselves to have 
the authority to authorize the United  States  to lift the confidentiality of its statements at the 
substantive meeting with the parties.857 Subsequently, in response to a formal request by the 
United  States , and following their consultation with the parties, the Panels adopted the ir Additional 
Working Procedures on 22  December 2016.858 
6.295.   We understand Mexico's challenge, in its Notice of Appeal, to the Panels' conduct of a 
"partially open meeting of the parties" to refer to the implementation of the Panels' Additional 
Workin g Procedures.859 Pursuant to these procedures, the Panels permitted the United  States ' 
request to disclose, through public viewing, the statements of its own positions made during the 
Panels' substantive meeting with the parties. The Panels also permitted an y third parties that so 
requested to disclose, through public viewing, the statements of their own positions made during 
the Panels' session with the third parties.860 The Panels granted these permissions on condition that 
                                                
849 Panel Re ports, para. 7.740.  
850 Mexico's Notice of Appeal, para.  11. See also Mexico's appellant's submission, para.  353(g).  While 
previous panels and the Appellate  Body have held meetings and hearings that were open to public observation, 
this is the first time tha t a WTO adjudicator authorized such a meeting without the express consent of both 
parties to the dispute. (See e.g. Panel Report, US – Tax Incentives , para.  1.20; Appellate  Body Report, EC and 
certain member States – Large Civil Aircraft (Article  21.5 – US), para.  1.30) 
851 United  States' appellee's submission, paras.  381-384. 
852 Panel Reports, paras.  1.14 and 1.16.  
853 Panel Reports, para.  1.18. 
854 The six third parties were Brazil, China, Ecuador, Guatemala, India, and Korea. (Panel  Reports, 
para. 7.14)  
855 The three third parties were Australia, Japan, and Norway. (Panel  Reports, para.  7.15)  
856 Panel Reports, para.  1.15. 
857 The Panels informed the parties of their decision through a joint communication with the Arbitrator 
acting under Article  22.6 of the DSU in the  same dispute. (Panel Reports, para.  1.17)  
858 Panel Reports, paras.  1.18-1.19. The Panels elaborated on their reasons for adopting these 
procedures in section  7.7.2 of their Reports.  
859 Panel Reports, Annex A -4. 
860 Seven third parties sought and were given pe rmission to disclose statements of their own positions 
during the Panels' session with the third parties (Australia, Canada, the European  Union, Japan, Korea, 
New Zealand, and Norway). (Panel Reports, fn  54 to para.  7.34)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  the public viewing take the form of  delayed (rather than simultaneous) viewing. The Panels also 
required that any parts of the meeting, including the third -party session, opened for partial public 
observation should not disclose statements of Mexico's positions or the po sitions of non -disclosing 
third parties. To this end, these parts of the meeting that were eventually opened for partial public 
observation were subjected to redaction prior to the public viewing.861 
6.296.   In explaining the ir reasons for the adoption of these Additional Working Proce dures, the 
Panels stated that:  
[I]t is … permissible  for a WTO adjudicator to authorize a request for a partially open 
meeting  if the conduct of such a meeting does not imp air or interfere with 
(a) a non-disclosing party's or non -disclosing third party's r ight to confidentiality 
protection of statements of its own position, (b) due process, (c)  the prompt settlement 
of disputes, or (d) the careful and efficient discharge, or the integrity, of the adjudicative 
function.862 
6.297.   According to the Panels, their Additi onal Working Procedures "fully protect[ed] Mexico's and 
non-disclosing third parties' right to confidentiality protection, satisf[ied] the requirements of due 
process, and [we]re sufficiently workable and efficient to safeguard the promptness of dispute 
settlement and the proper discharge and integrity of [the Panels'] adjudicative function".863 
6.3.2   Sufficiency of Mexico's Notice of Appeal  
6.298.   Mexico's Notice of Appeal identifies the alleged claim of error by the Panels as follows:  
Mexico also seeks review by the Appellate  Body of, and requests the Appellate  Body to 
reverse, the findings and conclusion of the Panels that they had the authority to conduct 
a partially open meeting of the parties without the consent of both Parties.864 
6.299.   The United  States challenges the sufficiency of Mexico's Notice of Appeal, arguing that it fails 
to meet the requirements of Rule  20(2)(d) of the Working Procedures.865 The United  States  contends 
that Mexico's Notice of Appeal fails to list any legal provision of any cov ered agreement that the 
Panels are alleged to have erred in interpreting or applying. The United  States  adds that Mexico's 
Notice of Appeal fails to indicate any paragraph of the Panel Reports containing the alleged errors.866 
The United  States  also asserts that, "[m]ore fundamentally", Mexico's Notice of Appeal fails to 
identify an alleged error in the issues of law covered in the Panel Reports or legal interpretation 
developed by the Panels.867 For the United  States , this means that Mexico  "has failed to just ify its 
appeal as being within the scope of Article  17.6 of the DSU".868 At the hearing, the United  States  
added that an appellant cannot cure a defect in the notice of appeal by including something additional 
in its appellant submission.  
6.300.   In response, at the  hearing, Mexico acknowledged that the notice of appeal serves to provide 
adequate notice to the appellee of the nature of the appeal and allegations of error, which  in turn 
enables the appellee to exercise fully its right of defence. At the same time, Mex ico highlighted that 
the Appellate  Body has stated that an appellee will have a better understanding of the nature of the 
appeal and the allegations of errors when a detailed written submission is filed on the same day. 
Given that Mexico's Notice of Appeal  and appellant's submission were filed on the same day, Mexico 
argued that the references to the relevant Panels' findings and legal interpretation could be clearly 
inferred from a review of both documents. In any event, Mexico contended that the perceived  failures 
of its Notice of Appeal had not prevented the United  States  from understanding the nature of 
Mexico's appeal on this matter, nor had the failures impeded the United  States ' ability to exercise 
its right of defence.  
                                                
861 Panel Reports, para.  7.34. 
862 Panel Reports, para.  7.31. 
863 Panel Reports, para.  7.32. 
864 Mexico's Notice of Appeal, para.  11. 
865 United  States' appellee's submission, paras.  381-384. 
866 United  States' appellee's submission, para.  385. 
867 United  States' appellee's submission, para.  387. 
868 United  States' appellee's submission, para.  389. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  6.301.   Rule 20(2)(d) of the Working Pr ocedures869 provides : 
(2) A Notice of Appeal shall include the following information:  
… 
(d) a brief statement of the nature of the appeal, including:  
(i) identification of the alleged errors in the issues of law covered in the panel report 
and legal interpre tations developed by the panel;  
(ii) a list of the legal provision(s) of the covered agreements that the panel is alleged 
to have erred in interpreting or applying; and  
(iii) without prejudice to the ability of the appellant to refer to other paragraphs of  
the panel report in the context of its appeal, an indicative list of the paragraphs of the  
panel report containing the alleged errors.  
6.302.   The Appellate  Body has referred to the notices of appeal and other appeal as the "documents 
that define the scope of the  appeal".870 In challenging the sufficiency of Mexico's Notice of Appeal, 
apart fro m noting certain formal defects , the United  States  expressed concern "[m]ore 
fundamentally" with the failure of Mexico's Notice of Appeal to identify "an alleged error in the issues 
of law covered in the Panel Reports or legal interpretation developed by the Panels " within the 
meaning of Rule  20(2)(d)(i) of the Working Procedures and Article  17.6 of the DSU.871 
6.303.   Article  17.6 of the DSU states that "[a]n appeal shall be limited to issues of law covered in 
the panel report and legal interpretations developed by the panel". Rule 20(2)(d)(i) of the 
Working  Procedures is rooted in the language of Article  17.6 of the DSU by req uiring a notice of 
appeal to include a "brief statement of the nature of the appeal, including identification of the alleged 
errors in the issues of law covered in the panel report and legal interpretations developed by the 
panel". Thus, Rule  20(2)(d)(i) r einforces the role of the notice of appeal as a document that defines 
the scope of the appeal872, within the boundaries delineated by Article  17.6 of the DS U. 
A fundamental consideration in determining whether a notice of appeal is sufficient, therefore, is 
whether the allegation of error identified in the notice of appeal is one that implicates "issues of law 
covered in the panel report and legal interpretations developed by the panel" as required by 
Article  17.6 of the DSU.  
6.304.   In the present dispute, Mexico ha s identified a decision made by the Panels regarding the 
conduct of their proceedings. In its Notice of Appeal, Mexico challenges "the findings and conclusion 
of the Panels that they had the authority to conduct a partially open meeting of the parties with out 
the consent of both Parties".873 As described above, as early as the organizational meeting s with the 
Panels, Mexico objected to the public observation of the Panels' substantive meeting with the parties, 
either fully or partially, without the consent of  both parties. The Notice of Appeal again identifies the 
same issue, that is, whether the Panels had the authority to conduct a meeting with the parties that 
was partially open to public observation without the consent of both parties. Mexico's Notice of 
Appeal, read in the context of the relevant procedural background leading to the Panels' findings, 
set out in paragraphs  6.292 -6.295  above,  appears to identify the issue of law as whether the Panels 
had the authority to conduct a meeting with the parties th at was partially open to public observation 
without the consent of both parties.  Hence , the allegation of error identified in paragraph  11 of 
Mexico's Notice of Appeal appears to be one that implicates an "issue[] of law covered in the panel 
report" as req uired by Article  17.6 of the DSU.  
6.305.   Moreover, in assessing whether Mexico's Notice of Appeal sufficiently identifies, pursuant to 
Rule 20(2)(d)(i) of the Working Procedures, "the alleged errors in the issues of law covered in the 
                                                
869 Working Procedures for Appellate Review, WT/AB/WP/6, 16  August 2010 (Working  Procedures).  
870 Working Procedures for Appellate Review, Communication from the Appellate  Body, 
WT/AB/WP/W/11, 27  July 2010, p.  5. 
871 United  States' appellee's submission, para.  387. 
872 Working Procedures for Appellate Review, Communication from the Appellate  Body, 
WT/AB/WP/W/11, 27  July 2010, p.  5. 
873 Mexico's Notice of Appeal, para.  11. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  panel report and legal inter pretations developed by the panel", we recall that the Appellate  Body 
has stated that the notice of appeal is not expected to contain the reasons why the appellant regards 
a panel's findings or interpretations as erroneous. Rather, the legal arguments in s upport of the 
allegations of error are to be set out and developed in the appellant's submission.874 We do not 
consider that Mexico's Notice of Appeal was required to go beyond identifying the alleged erroneous 
findings of the Panels and "contain the reasons  why [Mexico] regards those findings or 
interpretations as erroneous".875 In our view, such reasons were to be provided in Mexico's 
appellant's submission.  
6.306.   Furthermore, while we agree with the United  States  that a deficient notice of appeal cannot 
be cured b y including a new or additional issue in the appellant's submission876, we consider that 
the appellant's submission may be consulted in order to confirm the meaning of the words used in 
the notice of appeal.877 In its appellant's submission, Mexico points  out the aspects of the 
Panels'  reasoning with which it takes issue and explains why it considers the Panels' reasoning to be 
erroneous.878 For example, Mexico challenges the Panels' statement that "[i]f a WTO adjudicator has 
the power to accede to a request  to fully open a hearing or meeting with the parties, then a fortiori  
it must in principle also have the power to go less far, including by opening only parts of a meeting 
with the parties."879 Mexico contends that the Panels' statement is "incorrect" becaus e, in all prior 
disputes to which the Panels referred in support of this statement, there was an agreement of both 
disputing parties to open the meeting.880 As we see it, these statements in Mexico's appellant's 
submission confirm the Panels' decision with w hich Mexico takes issue in paragraph  11 of its 
Notice  of Appeal and provide the legal arguments in support of Mexico's claim of error.  
6.307.   We also take note of the United  States ' argument that Mexico has failed to justify its appeal 
as being within the scope o f Article  17.6 of the DSU because, "[r]ather than relating to the matter 
referred to the Panels by the DSB, Mexico's appeal relates to the procedures adopted by the Panels 
to conduct their proceedings."881 We do not agree. In our view, the manner in which a panel adopts 
procedures and conducts its proceedings when it addresses the matter referred to it by the DSB may 
give rise to issues of law and legal interpretation, which would be subject to the scope of appellate 
review within the meaning of Article  17.6.882 
6.308.   In addition to the United  States ' fundamental concern that Mexico's Notice of Appeal fails to 
comply with Article  17.6 of the DSU and Rule 20(2)(d)(i) of the Working  Procedures, the 
United  States  argues that Mexico's Notice of Appeal fails to comply with  the formal requirements set 
out in Rule  20(2)(d)(ii) and (iii) of the Working Procedures. The United  States  contends that Mexico's 
Notice of Appeal fails to refer to any legal provision of any covered agreement that the Panels are 
                                                
874 Appellate  Body Reports, US – Shrimp , para.  95; Indonesia – Iron or Steel Products , para.  5.6. It is 
noted that the statements by the Appellate  Body in US – Shrimp  concern an earlier version of the Working 
Procedures for Appellate Review. In those Working Procedures, Rule  20(2)(d) provided that a not ice of appeal 
shall include "a brief statement of the nature of the appeal, including the allegations of errors in the issues of 
law covered in the panel report and legal interpretations developed by the panel". (Appellate  Body Report,  
US – Shrimp , para.  95 (quoting Working Procedures for Appellate Review, WT/AB/WP/2, 28  February 1997))  
875 Appellate  Body Report, US – Shrimp , para.  95. See also Appellate  Body Report, Indonesia  – Iron or 
Steel Products , para.  5.6. 
876 This is especially so because Rule  23bis of the Working Procedures provides the avenue through 
which an appellant can amend its notice of appeal. Indeed, the Appellate  Body has, in the past, considered 
certain claims to fall outside the scope of the appeal where the appellant identified the claim o f error in the 
appellant's submission but not in the notice of appeal, as required by Rule  20(2)(d) of the Working Procedures. 
(See e.g. Appellate  Body Reports, US – Countervailing Measures on Certain EC Products , paras.  72-75;  
Japan – Apples , paras.  126-128) 
877 In this regard, we consider the statements by the Appellate  Body regarding the sufficiency of a panel 
request under Article  6.2 to be relevant, mutatis  mutandis , to the discussion of the sufficiency of a notice of 
appeal. In US – Carbon Steel , the A ppellate  Body found that a defect in the panel request cannot be cured by 
including a claim in a panel submission. Nevertheless, in considering the sufficiency of a panel request, 
submissions and statements made during the course of the panel proceedings m ay be consulted in order to 
confirm the meaning of the words used in the panel request. ( Appellate  Body Report, US – Carbon Steel , 
para. 127) 
878 Mexico's appellant's submission, paras.  341 and 344 (quoting Panel Reports, paras.  7.16 and 7.20).  
879 Mexico's ap pellant's submission, para.  341 (quoting Panel Reports, para.  7.16).  
880 Mexico's appellant's submission, para.  342. 
881 United  States' appellee's submission, para.  389. 
882 For example, in US – Shrimp , the Appellate  Body considered a challenge of "the [p]anel's  procedural 
finding that [it] lacked discretion to accept materials received from non -governmental sources" to be properly 
raised in the notice of appeal. (See Appellate  Body Report, US – Shrimp , paras.  94 and 96)  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  alleged to have erred in  interpreting or applying. The United  States  adds that Mexico's Notice of 
Appeal fails to indicate any paragraph of the Panel Reports containing the alleged errors.883 
6.309.   A notice of appeal must provide a brief statement of the nature of the appeal.884 Pursuant  to 
Rule 20(2)(d)(ii) and (iii) of the Working Procedures, this brief statement should include a list of the 
legal provisions of the covered agreements that the panel is alleged to have erred in interpreting or 
applying and an indicative list of the paragrap hs of the panel report containing the alleged errors. 
These two requirements facilitate the "identification of the alleged errors in the issues of law covered 
in the panel report and legal interpretations developed by the panel" as required by Rule  20(2)(d )(i) 
of the Working Procedures, read together with Article  17.6 of the DSU.  
6.310.   Mexico's Notice of Appeal does not include "an indicative list of the paragraphs" of the Panel 
Reports containing the alleged errors, as required by Rule  20(2)(d)(iii). Nor does Me xico's Notice of 
Appeal refer to "a list of the legal provision(s) of the covered agreements" that the Panels are alleged 
to have erred in interpreting or applying, as required by Rule  20(2)(d)(ii). The Appellate  Body has, 
in the past, considered such omissions to constitute "formal defects in the Notice of Appeal".885  
6.311.   Nonetheless, as the Appellate  Body highlighted in EC – Bananas III ( Article  21.5 – 
Ecuador  II) / EC – Bananas III ( Article  21.5 – US), Rule 20(2)(d) does  not stipulate what 
consequences flow from a failure to meet its formal requirements.886 In assessing the potential 
consequences of a failure of a notice of appeal to meet the formal requirements of Rule  20(2)(d)(ii) 
and (iii), the Appellate  Body has focused  on due process considerations.887 To this end, the 
Appellate  Body has taken into account the balance "that must be maintained between the right of 
Members to exercise the right of appeal meaningfully and effectively, and the right of appellees to 
receive no tice through the notice of appeal of the findings under appeal, so that they may exercise 
their right of defence effectively". Thus, the prospect of dismissal of an appeal because a notice of 
appeal fails to meet the formal requirements of Rule  20(d)(ii) a nd (iii) should be weighed against 
the possible denial of a party's right to appeal under Article  17.6 of the DSU. To the extent that an 
appellee "was placed on notice of the issues raised" in the notice of appeal,  the Appellate  Body has 
found that formal defects in the notice of appeal would not necessarily "give rise to procedural 
detriment of the kind that would warrant the dismissal" of the appeal.888 
6.312.   In the present dispute, while the United  States  points to these formal defects in Mexico's 
Notice of Appe al, the United  States  has not asserted that, owing to such formal defects, it did not 
receive sufficient notice of Mexico's appeal regarding the Panels' decision to conduct a partially 
opening meeting with the parties. Thus, despite Mexico's failure to com ply with the requirements in 
Rule 20(2)(d)(ii) and (iii), we consider that these formal defects do not, by themselves, warrant the 
dismissal of Mexico's appeal.  
6.313.   Based on the foregoing, we find that paragraph  11 of Mexico's Notice of Appeal sufficiently 
identifies an alleged error in the issues of law covered in the Panel Reports, as required by 
Rule 20(2)(d)(i) of the Working Procedures and Article  17.6 of the DSU. In  particular, Mexico's 
Notice of Appeal identifies, as an issue of law, the question whether  the Panels had the authority to 
conduct a meeting with the parties that was partially open to public observation without the consent 
of both parties. We also find that the formal defects in Mexico's Notice of Appeal, owing to Mexico's 
failure to comply wi th the requirements in Rule  20(2)(d)(ii) and (iii) of the Working Procedures, do 
                                                
883 United  States' appellee's submission, pa ra. 385. 
884 Rule 20(2)(d) of the Working Procedures.  
885 Appellate  Body Reports, EC – Bananas III (Article  21.5 – Ecuador II) / EC – Bananas III  
(Article  21.5 – US), para.  283. See also ibid., para.  279. 
886 Appellate  Body Reports, EC – Bananas III (Article  21.5 – Ecuador II) / EC – Bananas III  
(Article  21.5 – US), para.  280. 
887 Appellate  Body Reports, US – Countervailing Measures on Certain EC Products , para.  62; US – Offset 
Act (Byrd Amendment) , para.  206. In this regard, the Appellate  Body has also cautioned Members against 
drafting their notices of appeal or other appeal at a level of vagueness and imprecision that would make it 
"considerably difficult for the appellee, the third participants,  and the Appellate  Body to understand easily the 
full scope of [an appellant's] claim". Understanding the full scope of an appellant's claim should not require 
such effort. Drafting the notice of appeal or notice of other appeal with greater precision redu ces the risk of 
procedural objections and possible dismissal of a claim because it does not comply with the requirements of 
Rule 20 or 23 of the Working Procedures. (Appellate  Body Report, US – Large Civil Aircraft (2nd complaint) , 
para. 686) 
888 Appellate  Body Reports, EC – Bananas III (Article  21.5 – Ecuador II) / EC – Bananas III  
(Article  21.5 – US), para.  283. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  not, by themselves, warrant the dismissal of Mexico's appeal. We therefore find that Mexico's claim 
that the Panels erred in finding that they had the authority to conduct a p artially open meeting 
without the consent  of both parties is properly within the scope of this appeal.  
6.3.3   Whether the Appellate  Body  should rule on this issue  
6.314.   Having found that Mexico's allegation of error, as identified in paragraph  11 of Mexico's 
Notice of Appeal, is properly within the scope of this appeal, we take note of the suggestion  by the 
United  States  that, "it would be appropriate for the Appellate  Body to exercise judicial economy" 
with respect to this claim of error. In the United  States ' view, th is is because Mexico's appeal of the 
Panels' decision to conduct the partially open panel meeting does not concern "issues of law covered 
in the panel report" or "legal interpretations developed by the panel".889 
6.315.   As a preliminary matter, we recall our findin g above that paragraph  11 of Mexico's Notice of 
Appeal sufficiently identifies, as an issue of law, the question whether the Panels had the authority 
to conduct a meeting with the parties that was partially open to public observation without the 
consent of  both parties.890 We therefore disagree with the United  States  that Mexico's appeal does 
not concern "issues of law covered in the panel report".  
6.316.   This, however, does not necessarily mean that a finding on this aspect of Mexico's appeal is 
required. The following provisions of the DSU are relevant in this regard. Article  17.12 provides that 
"[t]he Appellate  Body shall address each of the issues raise d in accordance with paragraph  6 during 
the appellate proceeding ."891 Article  3.2 states that:  
The dispute settlement system of the WTO is a central element in providing security 
and predictability to the multilateral trading system. The Members recognize th at it 
serves to preserve the rights and obligations of Members under the covered 
agreements, and to clarify the existing provisions of those agreements in accordance 
with customary rules of interpretation of public international law. Recommendations and 
rulings of the DSB cannot add to or diminish the rights and obligations provided in the 
covered agreements.  
6.317.   Article  3.4 provides that "[r]ecommendations or rulings made by the DSB shall be aimed at 
achieving a satisfactory settlement of the matter". Article  3.7 states that "[t]he aim of the dispute 
settlement mechanism is to secure a positive solution to a dispute ." 
6.318.   In the past, the Appellate  Body has understood these overarching aims of the WTO  dispute 
settlement mechanism to mean that, while the Appellate  Body is required to address each issue on 
appeal, it has the discretion not to rule on an issue when doing so is not necessary to resolve the 
dispute892, but the Appellate  Body may rule on such an issue in light of the specific circumstances 
of a given disput e.893 
6.319.   Turning to the specific circumstances of these proceedings, we note the following competing 
considerations that are relevant to our decision on whether ruling on Mexico's claim of error is 
necessary. First, the issue raised by Mexico's appeal does not directly relate to the "matter [at] issue 
                                                
889 United  States' appellee's submission, para.  390. 
890 See para. 6.313 above.  
891 Article  17.6 limits an appeal to "issues of law covered in the panel  report and legal interpretations 
developed by the panel".  
892 Appellate  Body Report, US – Upland Cotton , paras.  510-511. On many of the occasions where the 
Appellate  Body found that ruling on an issue would be unnecessary to resolve a dispute, this finding was made 
after the Appellate  Body had already found an error or inconsistency under a related substantive claim. (See 
e.g. Appellate  Body Reports, EU – Biodiesel (Argentina) , para.  6.89; US – Zeroing (Japan) , para.  140;  
US – Gambling , para.  156; EC – Selected Customs Matters , para.  243) However, these examples are not 
exhaustive in identifying the circumstances in which it would be appropriate for the Appellate  Body to find that 
ruling on an issue would be unnecessary to resolve a dispute. (See e.g. Appell ate Body Reports, EU – Fatty 
Alcohols (Indonesia) , para.  5.252; US – Upland Cotton , paras.  510-511; US – Steel Safeguards , 
paras.  483-484) 
893 Appellate  Body Report,  China – HP-SSST (EU) , paras.  5.310 and 5.317. See also Appellate  Body 
Report, US – Upland Co tton, para.  510. WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  in the dispute"894, that is, whether the 2016 Tuna Measure is consistent with the TBT Agreement  
and the GATT  1994.895 At the same time, we recognize that the manner in which a panel adopts 
procedures and conducts its p roceedings when it addresses the matter referred to it by the DSB may 
give rise to issues of law and legal interpretation, which would be subject to the scope of appellate 
review within the meaning of Article  17.6 of the DSU.896 Second, Mexico considers that  the Panels 
were not authorized to partially open their meeting with the parties to public observation without 
the consent of Mexico. Hence, in its appellant's submission, Mexico requests us to find that the 
"Panels erred … in directing that the hearing be  partially opened to the public when Mexico did not 
agree to the opening" in this case.897 However, Mexico's arguments on appeal do not elaborate on 
the manner in which the Panels' decision is inconsistent with the DSU.898 Third, in addition to Mexico's 
reques t above for a finding of error, Mexico requests "that the Appellate  Body clarify that, in the 
future , panels should not open a hearing even partially without the agreement of all disputing 
parties".899 Mexico suggested that, by ruling on this issue, the Appe llate Body would be providing 
clarification on a concern that impacts not only panels but also arbitrators under Article  22.6 of the 
DSU.900 The fact that Mexico's request concerns the proceedings of other panels and arbitrators 
casts doubt on whether ruling  on this issue is necessary to resolve the present dispute.  
6.320.   In light of the specific circumstances of these proceedings as set out above, we find it 
unnecessary to rule  on whether the Panels erred in finding that they had the authority to conduct a 
partially open meeting of the parties without the consent of both parties. Our finding should not be 
construed as an endorsement of the Panels' decision  to conduct a partially open meeting of the 
parties wi thout the consent of both parties.901 
7  FINDINGS AND CONCLUS IONS  
7.1.  For the reasons set out in this Report, the Appellate  Body makes the following findings and 
conclusions:  
7.1  Whether the Panels erred in their findings under  Article  2.1 of the TBT Agreement   
7.2.  Under Article 2.1 of the TBT Agreement , in order to determine whether the detrimental impact 
stems exclusively from a legitimate regulatory distinction, a panel must carefully scrutinize whether 
the technical regulation at issue is even -handed in light of the par ticular circumstances of the case. 
In the present dispute, an examination of whether the 2016 Tuna Measure is consistent with 
Article  2.1 of the TBT Agreement  entails an assessment of whether the regulatory distinctions of the 
measure are calibrated to the  risks to dolphins arising from different fishing methods in different 
areas of the ocean. Such assessment involves:  (i) an assessment of the overall relative risks of harm 
to dolphins arising from the use of different fishing methods in different ocean ar eas; and 
(ii) an assessment as to whether the differences in the dolphin -safe labelling conditions under the 
measure are appropriately tailored to, or commensurate with, those respective risks. If conducted  
properly , this calibration analysis would  encompass consideration of the rational relationship 
between the regulatory distinctions drawn by the 2016 Tuna Measure and its objectives. Thus, there 
is no need to separately assess the rational relationship between the regulatory distinctions drawn 
by the measure and its objectives. Furthermore, while risks of inaccurate labelling are relevant to 
the calibration analysis, this does not mean that the applicable legal standard requires the Panel s to 
                                                
894 Appellate  Body Report, US – Wool Shirts and Blouses , p. 19, DSR  1997:I, p.  340. See also 
Appellate  Body Reports, EU – PET (Pakistan) , para.  5.28; India – Patents (US) , para.  87; Brazil – Retreaded 
Tyres , para.  257; Canada – Wheat Exports  and Grain Imports , para.  133; US – Lead and Bismuth  II, paras.  71 
and 73; Argentina  – Footwear (EC) , para.  145; Australia – Salmon , para.  223; Japan – Agricultural Products II , 
para. 111. 
895 United  States' panel request; Mexico's panel request.  
896 See para. 6.307 above.  
897 Mexico's appellant's submission, para.  353. 
898 In this regard, we take note of the United  States' assertion that "the DSU does not impose any 
conditions on either opening the hearing or closing the hearing to the public." (United  States' appellee's 
submission, para.  396) 
899 Mexico's appellant's submiss ion, para.  352. (emphasis added)  
900 Mexico's response to questioning at the hearing.  
901 Paragraph  2 of Appendix  3 to the DSU states that "[t]he panel shall meet in closed session" and that 
"[t]he parties to the dispute, and interested parties, shall be prese nt at the meetings only when invited by the 
panel to appear before it." Article  12.1 of the DSU states that "[p]anels shall follow the Working Procedures in 
Appendix  3 unless the panel decides otherwise after consulting the parties to the dispute."  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  determine whether the 2016  Tuna Measure is calibrated, inter alia , to the risk of inaccurate 
dolphin -safe information being passed to consumers.  
7.3.  In conducting the calibration analysis, it is necessary to examine the risks to dolphins across 
all relevant ocean areas in which different fishing methods are practi sed. This does not mean that, 
under Article  2.1 of the TBT Agreement , a measure that seeks to protect dolphins must make all 
relevant regulatory distinctions on the basis of both fishing method and ocean area. Rather, the 
nature of the calibration analysis to be conducted is informed by the nature of the regulatory 
distinctions made under the measure itself, and it is the regulatory distinctions causing the 
detrimental impact on imported products that must be calibrated to different risks to dolphins. The 
relevant regulatory distinctions that need to be examined for the purpose of calibration in this dispute 
include the distinction between setting on dolphins and other fishing methods (in the context of the 
eligibility criteria) and the distinction between th e ETP large purse seine fishery and all other fisheries 
(in the context of the certification and the tracking and verification requirements).  
7.4.  For these reasons, we do not consider that Mexico has established that the Panels, in 
considering that they were required to examine whether the 2016 Tuna Measure was calibrated to 
the risks to dolphins arising from the use of different fishing methods in different areas of the ocean, 
failed to include an inquiry into the nexus between the relevant regulatory distinc tions and the 
objectives of the measure. We also disagree with Mexico that the Panels erred by comparing the risk 
profiles of different fishing methods in applying the calibration analysis to the eligibility criteria. In 
our view, in the specific context o f the 2016 Tuna Measure, in order to assess whether the 
detrimental impact on Mexican tuna products stems exclusively from a legitimate regulatory 
distinction, the Panels were required to assess whether the regulatory distinctions causing that 
detrimental impact are calibrated to different risks to dolphins, in terms of the overall relative risks 
to dolphins, taking into account the objectives of the measure.  
7.5.  In conducting their examination of the risk profiles of different fishing methods as used in 
different ocean areas, the Panels reviewed  all relevant evidence of risks to dolphins as provided to 
them by the parties, including all evidence pertaining to individual fisheries. Additionally, the Panels 
appropriately took into account all relevant types of ha rm to dolphins in assessing the risk profiles 
of different fishing methods and fisheries. Moreover, the Panels did not err in relying on per set data 
as the primary measurement of the risks to dolphins, despite three additional measurements 
proposed by Mex ico. First, because the relevant risks to be assessed for the purpose of calibration 
are the risks of individual dolphins being harmed or killed in the fishing process, the Panels were 
correct not to rely on PBR evidence  to assess the risks to dolphins. Se cond, given the comparative 
nature of the calibration analysis, the Panels did not err by relying primarily on a per set 
methodology, instead of a comparison of absolute levels of harm. Finally, Mexico did not substantiate 
its assertion that tuna fishing i n ocean areas with less reliable regulatory systems is more likely to 
lead to harm to dolphins, and therefore the Panels did not err by excluding evidence pertaining to 
regulatory oversight from their assessment of the overall relative risks to dolphins fr om the use of 
different fishing methods as used in different areas of the ocean. We therefore find no error in the 
Panels' assessment of the risks to dolphins arising from the use of different fishing methods in 
different ocean areas  or in their conclusion s regarding the risk profiles of relevant fishing methods 
on the basis of that assessment.  
7.6.  Regarding whether the 2016 Tuna Measure is calibrated to the risks to dolphins arising from 
the use of different fishing methods in different ocean areas, we have ad dressed Mexico's challenges 
to the Panels' assessment of the following aspects of the 2016 Tuna Measure: (i)  the eligibility 
criteria; (ii)  the certification requirements; (i ii) the tracking and verification requirements; and 
(iv) the 2016 Tuna Measure as a whole.  
7.7.  With respect to the eligibility criteria, we have found that the Panels did not err in finding, in 
paragraph 7.539 of their Reports, that "setting on dolphins is significantly more dangerous to 
dolphins than are other fishing methods ." This finding implies that the distinction in the eligibility 
criteria between setting on dolphins, on the one hand, and other fishing methods, on the other hand, 
is, as the Panels found in paragraph 7.540 of their Reports, "appropriately calibrated to th e risks to 
dolphins arising from the use of different fishing methods in different areas of the ocean". 
Accordingly, we find that Mexico has not demonstrated that the Panels erred  in reaching the 
intermediate finding, in paragraph  7.547 of their Reports, that the eligibility criteria embodied in the 
2016 Tuna Measure are calibrated to the risks to dolphins arising from the use of different fishing 
methods in different areas of the ocean.  WT/DS381/AB/RW/USA • WT/DS381/AB/RW2  
 
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  7.8.  With respect to the certification requirements, we have found that the  Panels adopted the 
correct approach in comparing the risk profiles of individual fisheries, because the certification 
requirements make a distinction  on the basis of both fishing method and ocean area. Having found 
no legal error in the Panels' assessment  of risk profiles, we consider that the Panels did not err in 
finding that the ETP large purse seine fishery has a special risk profile that distinguishes it from other 
fisheries. We have also addressed and rejected all of Mexico's ar guments challenging th e 
Panels'  assessment of the certification requirements , including the allegation that  the Panels did not 
take into account the risks of inaccuracy in their calibration analysis . For all of these re asons, 
we find that Mexico has not demonstrated that the Pa nels erred in arriving at the intermediate 
finding, in paragraph 7.611 of their Reports, that the different certification requirements are 
calibrated to the risks to dolphins arising from the use of different fishing methods in different areas 
of the ocean . 
7.9.  As with the certification requirements, we have found that with respect to the tracking and 
verification requirements, the Panels adopted the correct approach in comparing the risk profiles of 
individual fisheries, because these requirements make a disti nction on the basis of both fishing 
method and ocean area. Having found no legal error in the Panels' assessment of risk profiles, we 
consider that the Panels did not err in finding that it is both the technical and legal possibilit ies of 
setting on dolphi ns and the fact that dolphin sets occur in a consistent and systematic manner in 
the ETP large purse seine fishery that give this fishery its special risk profile. Moreover, we have 
rejected Mexico's claims that (i)  the Panels erred in their evaluation of the tracking and verification 
requirements , including the allegation that the Panels did not take into account the risks of 
inaccuracy ; and (ii)  the Panels failed to make an objective assessment of the facts of the case as 
required under Article  11 of the DSU. Consequently , we find that Mexico has not demonstrated that 
the Panels erred in arriving at the intermediate finding, in paragraph  7.676 of their Reports, that:  
[A]lthough there remain differences between the NOAA and AIDCP regimes with respect 
to tracking and verification, the Panels are of the view that such differences have been 
considerably narrowed in the 2016  Tuna Measure and the Panels find that the remaining 
differences are calibrated to the differences in the risk profile of the ETP large p urse 
seine fishery compared to other fisheries.  
7.10.   We further consider that the Panels' analyses of e ach of the elements of the 2016  Tuna 
Measure, as well as their examination of the measure as a whole, were properly informed by the 
interlinkages between thes e elements and the fact that they operate together to regulate access to 
the dolphin -safe label. Furthermore, we recall that Mexico's appeal in this regard is consequential 
upon its challenge of the Panels' assessment of the eligibility criteria, certifica tion requirements, and 
tracking and verification requirements. Having reviewed and rejected Mexico's arguments against 
the Panels' assessment of each of these elements of the 2016 Tuna Measure, we find that Mexico 
has not demonstrated that the Panels erred  in their assessment of the 2016  Tuna Measure, as a 
whole, or in finding, in paragraph  7.717 of their Reports,  that the 2016  Tuna Measure, as a whole, 
is calibrated to the risks to dolphins arising from the use of different fishing methods in different 
areas of the ocean.  
7.11.   Based on our analyses and findings above , we uphold  the Panels' conclusion , in 
paragraphs  7.717, 8.2, and 8.6 of the  Panel  Reports, that the 2016  Tuna Measure accords to Mexican 
tuna products treatment no less favourable than that accorded  to like products from the 
United  States  and other countries and therefore is consistent with Article  2.1 of the TBT Agreement . 
7.2  Whether the Panel s erred in their findings under  Article  XX of the GATT  1994  
7.12.   One of the most important factors in the assessment of arbitrary or unjustifiable 
discrimination under the chapeau  of Article  XX of the GATT 1994  is the question of whether the 
discrimination can be reconciled with, or is rationally related to, the policy o bjective with respect to 
which the measure has been provisionally justified under one of the subparagraphs of Article  XX. As 
indicated above, the Appellate  Body's guidance in the first compliance proceedings indicates that the 
calibration analysis is the t ool in the circumstances of this dispute to assess whether the 2016  Tuna 
Measure is consistent with Article  2.1 of the TBT Agreement . If done  properly , the calibration 
analysis would encompass consideration of the rational relationship between the regulato ry 
distinction of the 2016  Tuna Measure and its objectives. As also indicated , it was appropriate for the 
Panels, in the circumstances of these compliance proceedings, to rely on their calibration analysis 
under Article  2.1 in their assessment of whether t he 2016  Tuna Measure is applied in a manner that