The growing network of Regional Trade Agreements (RTAs) concluded between States has often been seen as a threat or policy alternative to the multilateral World Trade Organization (WTO) system. This dissertation re-evaluates this assumption by examining the interaction between WTO law and the RTA network. Focusing on the role of norms, institutions, and legal processes, it shows how this interaction has led to the development of international trade law into a legal system of international law.

The argument is developed in five parts. First, the dissertation explores the concept of a ‘legal system’ and addresses how the continued interaction between WTO law and RTAs is formative of international trade law as a legal system of international law. Second, it is argued that rights and obligations under the WTO Agreement cannot be modified inter se based on Article 41 Vienna Convention on the Law of Treaties. As such, Members may only lawfully conclude inter se treaties which are compatible with existing WTO norms, fall within the scope of an exception, or are authorised through a waiver. Third, it is shown that RTA exceptions found in WTO covered agreements serve a public ordering function by defining the range of permissible RTA formations which could be established. At the same time, the conditions found in these provisions operate as incomplete bargains by setting out hermeneutically ambiguous disciplines that have not been clarified through treaty interpretation due to the reluctance of WTO Members to interpret them. Fourth, it explains how the expansion of international trade law is in part facilitated through norm dispersal processes – where norms found in one treaty are subsequently incorporated into another. However, these processes do not necessarily ensure the consistent interpretation and application of norms across international trade law, as this would depend on whether there are relevant differences between the norm-sharing treaties and the adopted method of norm incorporation. Finally, it is suggested that the WTO Appellate Body and panels may rely on the good faith obligation under Articles 3.7 and 3.10 DSU and where ‘actions’ brought by Members are not ‘fruitful’ under Article 3.7 DSU to refuse to exercise their jurisdiction where there is jurisdictional overlap. In turn, RTA tribunals may generally rely on both their express and inherent powers to refuse to exercise jurisdiction, particularly the principles of res judicata and lis pendens.