Obligations Erga Omnes (Partes) and the Participation of Third States in Inter-State Litigation

This article addresses the role of third States in public interest litigation – i.e., ongoing proceedings concerning interests which they share with the international community. It scrutinizes third-State intervention in inter-State cases through the prism of rules and principles arising in public interest litigation, and aims to clarify the limits of such participation. Having synthesized the relevant law and doctrine of intervention practice before the ICJ and other institutional courts, it considers the extent to which third-State interests find expression through Articles 62 and 63 of the ICJ Statute. It examines the invocation of international legal responsibility on the basis of obligations erga omnes and erga omnes partes, as well as the prospect of intervention on this basis. It then identifies and addresses jurisdictional and procedural questions arising in these and other instances of “public interest” intervention. It concludes by envisaging the prospective institutional development of multilateral participation in public interest litigation.