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* Associate Professor of Law, Duke University School of Law. Formerly with the Legal Affairs Division andAppellate Body Secretariat of the WTO. This paper is a substantial revision of Part I of The Natureof WTO Obligations, Jean Monnet Working Paper No. 1/02 (2002), posted athttp://www.jeanmonnetprogram.org/papers/02/020101.html. It was conceived partly during an EmilNoel Fellowship at NYU Law School for which I remain extremely grateful to Joseph H.H. Weiler. Manythanks also for discussions and critical evaluations to James Crawford, Lothar Ehring, Robert Lawrence,Petros Mavroidis, Bruno Simma and the anonymous reviewers of the EJIL.

..............................................................................................................................................................EJIL (2003), Vol. 14 No. 5, 907951

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A Typology of MultilateralTreaty Obligations: Are WTOObligations Bilateral orCollective in Nature?

Joost Pauwelyn*

AbstractAn important, though oft neglected, distinction between multilateral treaty obligationsseparates obligations of a bilateral nature from those of the collective or erga omnes partestype. Multilateral obligations of the bilateral type can be reduced to a compilation of bilateral,state-to-state relations. They can be compared to contracts. Collective obligations, incontrast, cannot be divided into bilateral components. They are concluded in pursuit of acollective interest that transcends the individual interests of the contracting parties. Thestandard example of such obligations are those arising under a human rights treaty. Indomestic law, collective obligations can be compared to criminal law statutes or evendomestic constitutions. This essay examines the origins of the distinction between bilateraland collective obligations, as well as its major consequences, both in the law of treaties andthe law on state responsibility. On that basis, a wider typology of multilateral treatyobligations is suggested. In the exercise, obligations arising under the World TradeOrganization are used as a case study. The argument is made that WTO obligations remainessentially of the bilateral type; they are not collective in nature.

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1 Article 19 of the 1996 Draft Articles on State Responsibility of the International Law Commission (ILC),ILC Report on the 48th Session, UN Doc. A/51/10, 125 et seq. (hereafter ILC Draft). Among the manydiscussions on Article 19 see, for example, J. Weiler, A. Cassese and M. Spinedi (eds), International crimesof state: a critical analysis of the ILCs Draft Article 19 on state Responsibility (1989) and Pellet, Can a StateCommit a Crime? Definitely, Yes!, 10 EJIL (1999), at 425434.

2 Article 48 of the 2001 Articles on State Responsibility of the ILC, ILC Report on the 53rd Session, UN Doc.A/56/10, 43 et seq. (hereafter ILC Articles). For recent discussions, see the collection of articles inSymposium: The ILCs State Responsibility Articles, 96 AJIL (2002), at 773, and Symposium: Assessingthe Work of the International Law Commission on State Responsibility, 13 EJIL (2002), at 1053.

3 For a noticeable but limited exception (limited, as it focuses more on peremptory norms and erga omnesobligations than collective versus bilateral obligations), see Sicilianos, The Classification of Obligationsand the Multilateral Dimension of the Relations of International Responsibility, 13 EJIL (2002), at11271145.

4 The notion of a multilateral treaty as bundles of bilateral rights and obligations was introduced inSimma, Bilateralism and Community Interest in the Law of state Responsibility, in Y. Dinstein and M.Tabory (eds), International Law at a Time of Perplexity: Essays in Honor of Shabtai Rosenne (1989), at821822 (infra note 78).

5 However, as explained below, collective obligations consist of both obligations erga omnes partes andobligations erga omnes.

1 IntroductionAmidst the storm of discussion over international crimes1 and obligations owed tothe international community as a whole,2 another classification in the InternationalLaw Commission (ILC) Articles on State Responsibility has almost gone unnoticed.3 Itis the distinction between (i) multilateral treaty obligations that can be reduced to acompilation or bundle of bilateral relations,4 each of them detachable one from theother; and (ii) multilateral treaty obligations whose binding effect is collective andcannot be separated into bilateral components, on the ground that they are concludedfor the protection of a collective interest, over and above any interests of thecontracting parties individually. The former (bundles of bilateral relations) give rise towhat we shall name bilateral obligations, the latter (concluded in the collectiveinterest) lead to what can be referred to as collective obligations or obligations ergaomnes partes.5

This essay examines the origins of the distinction between bilateral and collectiveobligations, as well as its major consequences, both in the law of treaties and the lawon state responsibility. The Marrakesh Agreement Establishing the World TradeOrganization (WTO) will serve as a case study for this purpose. As further explainedbelow, classifying WTO obligations as either bilateral or collective in nature hascrucial legal consequences. It affects (a) rules on standing (who can invokeresponsibility for breach of WTO law and what claims can they make?); (b) thepermissibility to suspend WTO obligations as a form of countermeasure in response tobreach (be it breach of WTO law itself or breach of other obligations of internationallaw); (c) the way in which WTO Members can respond to non-compliance (inparticular, the scope for a WTO violation to continue pursuant to a bilateralsettlement); and, perhaps most importantly, (d) the possibility that subsequenttreaties, between certain WTO Members only, prevail over earlier WTO treaty norms

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6 The contract versus crime analogy is referred to in R. Lawrence, Crime and Punishments? An Analysis ofRetaliation under the WTO, manuscript on file with the author. The contract versus statute paradigm is notnew. See, for example, Reuter, Solidarit et divisibilit des engagements conventionnels, in Y. Dinsteinand M. Tabory (eds), International Law at a Time of Perplexity Essays in Honour of Shabtai Rosenne(Dordrecht, 1998), at 623.

7 As Oscar Schachter noted, (t)he distinction [between what we call bilateral and collective obligations] is,of course, a familiar one, although the line between the two categories is sometimes blurred; Schachter,Entangled Treaty and Custom, in Y. Dinstein and M. Tabory (eds), International Law at a Time ofPerplexity Essays in Honour of Shabtai Rosenne (Dordrecht, 1998), at 735.

(in technical terms, the legality of inter se modifications to the WTO treaty). Moregenerally, classifying WTO obligations as bundles of bilateral obligations would bringthem closer to the domestic law analogy of a contract. Construing WTO obligations ascollective in nature would make them comparable to a domestic criminal law statuteor even domestic constitutions.6

Our analysis will proceed as follows. Section 2 traces the origins and currentrelevance of the distinction between bilateral and collective obligations. It ends withtwo tables setting out a suggested typology of international obligations. Section 3attempts to answer the question of whether WTO obligations are bilateral or collectivein nature. The argument made is that, having weighed the different factors, WTOobligations should be seen as bilateral obligations. Section 4 sums up the conse-quences of the bilateral nature of WTO obligations, taking into account both generalinternational law and the lex specialis provided for in the WTO treaty itself. Section 5concludes this analysis.

The main objective of this paper is to draw attention to important differencesbetween types of multilateral treaty obligations, and to illustrate the uneasy7 yetcrucially important task of deciding which category a particular obligation belongsto. From a normative perspective, the argument that WTO obligations are bilateralobligations has both positive and negative consequences. It may not, therefore, beuniversally shared, nor should it always remain valid in the light of futuredevelopments. Yet it is hoped that presenting this specific WTO puzzle will prove usefulboth for a better understanding of the WTO system itself and of other multilateraltreaty regimes.

2 Origins, Forms and Consequences of the Distinctionbetween Bilateral and Collective Obligations

A Early PCIJ and ICJ CasesThe Reservations to the Genocide Convention case (1951) presents one of the first signs ofthe distinction between bilateral and collective obligations. In that case, the ICJ gaveparticular importance to the objects of the Convention. It noted that [t]heConvention was manifestly adopted for a purely humanitarian and civilizing purpose.It is indeed difficult to imagine a convention that might have this dual character to agreater degree, since its object on the one hand is to safeguard the very existence ofcertain human groups and on the other to confirm and endorse the most elementary

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