The Process of International Law— Making: The Relationship Between the International Court of Justice and the International Law Commission

Article 38, para.1, of the Statute of the International Court of Justice (ICJ) defines customary international law as evidence of general practice accepted as law, understood as State practice and opinio juris. However, by identifying certain norms as an international custom without referring to the traditional evidence of State practice and opinio juris, international courts and tribunals are contributing to the formation of customary international law. This paper presents an analysis of how the International Court of Justice contributes to the formation of customary international law by relying on the draft articles of the International Law Commission (ILC). Th e International Court of Justice, in “deciding in accordance with international law”, also authoritatively declares what the current international law is, while the International Law Commission, although constituted of highly qualified publicists from various States, is drafting only non-binding international instruments. By relying on the ILC draft articles and declaring them to be reflecting customary international law-although the draft articles may not be necessary the expression of the States’ practice and their opinio juris, the ICJ creates and generates the creation of customary international law. Interestingly, the ICJ tends to rely mostly on ILC draft articles that refer to the jurisprudence of either the Permanent Court of International Justice (“PCIJ”) or the ICJ itself. Th e paper presents research of approximately 70 ICJ decisions and individual opinions that cite to the work of the ILC. The author notes the evolution of the relationship between the ICJ and the ILC through three different time periods, and presents the findings on how, when and why the ICJ relies on the ILC draft articles. In addition, the author gives examples in which the ICJ rejected the reliance on the ILC’s work, mainly due to the divergent interpretation on the specific area of international law. The ICJ, by relying on the ILC draft articles that in turn refer to the jurisprudence of the ICJ or PCIJ, is not only generating norms of customary international law, but is also reaffirming the importance of its (and PCIJ’s) jurisprudence for the future of international law. Although ICJ decisions are binding only between the parties to the dispute (Art.59 ICJ Statute), the clarification of whether a norm is customary or not, affects the international community of States. Noting the present reluctance of States to adopt treaties, and- hence their potentially decreasing role in international law-making, this research offers an insight into an alternative venue of international law-making. As the international community, and the ILC itself, is regaining interest in the sources of international law, this paper aims to identify the mechanisms of international law-making, the understanding of which will contribute to international law’s needed predictability and a more uniform and reliable interpretation of international law.