Introduction

This chapter reviews WTO jurisprudence on general international law concepts and principles concerning conflicts between treaties. The problem of treaty conflicts was discussed by the earliest writers on public international law, and has attracted considerable attention in recent years. In 2006, an ILC study group issued an analytical study addressing related concepts and principles of general international law, including but not limited to the principle of lex specialis, the rules governing conflicts between successive norms, and the principle of treaty interpretation reflected in Article 31(3)(c) of the Vienna Convention. These and other concepts and principles relating to treaty conflicts have been the subject of extensive commentary in the context of WTO law, for two different reasons. First, the WTO Agreement is a complex treaty comprising a series of overlapping agreements and instruments, and therefore WTO adjudicators have had to address various questions about the relationship among the different agreements and instruments that constitute the overall WTO treaty. Second, there have been several GATT/WTO proceedings in which the respondent argued that the challenged measure was required or permitted under a non-WTO treaty, or that the WTO obligation was superseded or otherwise rendered inapplicable by that treaty (e.g. a multilateral environmental agreement, a bilateral trade agreement and/or another international legal instrument). The WTO agreements contain some provisions for resolving conflicts among the agreements and instruments that comprise the WTO treaty. However, many issues are left unregulated by the text of the WTO agreements including, for example, what constitutes a ‘conflict’. This has left some scope for general international law concepts and principles relating to treaty conflicts to be taken into account by WTO adjudicators. This chapter reviews statements by WTO adjudicators related to seven different ways to avoid or resolve treaty conflicts: (i) applying the narrow definition of and presumption against ‘conflict’ in international law; (ii) applying the principle of treaty interpretation reflected in Article 31(3)(c) of the Vienna Convention; (iii) using treaties as evidence of facts; (iv) applying priority clauses;