This article discusses the long-standing issue of jurisdictional conflict in World Trade Organisation (WTO) jurisprudence, which has, in the recent decades, been exacerbated by the proliferation of Regional Trade Agreements (RTAs). An examination of WTO jurisprudence reveals that jurisdictional conflict stems from the lack of choice of forum clauses in WTO-covered agreements, and the lack of a hierarchy of sources in international law. While there exists legal basis for the application of general principles of international law such as res judicata, a careful analysis demonstrates that there is conceptual difficulty applying the doctrine in the context of WTO disputes. To remedy this, the article argues that the WTO Dispute Settlement Understanding (DSU) could be amended to allow for the operation of res judicata.