Using res judicata to resolve jurisdictional conflicts between WTO and regional trade agreements’ dispute settlement mechanisms

The WTO has a renowned dispute settlement body, distinguished from other dispute settlement bodies by its compulsory and exclusive jurisdiction. However, regional trade agreements provide for rights and obligations similar to those guaranteed by the WTO thus, causing material jurisdictional overlaps between the WTO institutions and regional dispute resolution institutions. Potentially, a State aggrieved by measures that contravene rights or obligations within such overlaps has two alternative fora for dispute resolution. Where the regional trade agreement dispute resolution mechanism resolves the dispute first, the compulsory and exclusive nature of the WTO jurisdiction allows the matter to be re-determined at the WTO level, causing jurisdictional conflicts and duplicative proceedings. Although it is an established principle in customary international law, res judicata is not provided in any of the instruments guiding the jurisdiction of the WTO dispute settlement system. The jurisprudence of WTO Panels and the Appellate Body are also thin on this matter. Seemingly, the inclination has been to exercise the compulsory and exclusive jurisdiction, without regard to other existing fora. This paper therefore suggests clear recommendations to be employed in widening the existing WTO jurisprudence on res judicata as a solution to jurisdictional conflicts. In doing so, this paper further acknowledges the possible criticisms against res judicata in WTO dispute settlement and provides possible solutions to these challenges to ensure the peaceful and harmonious coexistence of the WTO dispute settlement mechanisms vis-à-vis those of regional trade agreements. Using the South American region as an example, this paper enunciates the jurisdictional overlaps and proposes the application of res judicata by the WTO dispute settlement mechanisms in judicial restraint