The rules of customary international law governing when a state or international organization will be held to have committed an internationally wrongful act, thereby engaging its international responsibility, are relatively well settled in international practice and jurisprudence. A key point of reference in this regard is the work of the International Law Commission on State Responsibility and Responsibility of International Organizations. The present paper examines relevant practice of domestic courts from a variety of jurisdictions which have relied upon the ILC's work, and discusses the extent to which domestic courts may make a contribution to the further development of the rules relating to engagement of responsibility. It concludes that, due to the operation of rules of, inter alia, immunity and non-justiciability, the principal instance in which domestic courts may actually apply the rules of international law is where it is the responsibility of the forum state which is in issue.
