The International Court of Justice and the Concept of State Practice

91 Pages Posted: 12 Oct 2008

See all articles by Mark Weisburd

Mark Weisburd

University of North Carolina School of Law


State practice is an important element of international law, both as a key component of customary international law and as a crucial tool for interpreting treaties. In this paper, Professor Weisburd seeks to show that there are important flaws in the application of state practice by the International Court of Justice. The Court has relied on actual practice to determine the content of customary rules surprisingly rarely, frequently basing its conclusions instead on non-binding actions by international bodies or on its own decisions. It has reached decisions in some cases clearly inconsistent with significant and relevant state practice and in others proclaimed as rules of law formulations unsupported by state behavior. The Court has been inconsistent in its treatment of the practice of parties to treaties in cases presenting interpretation questions, sometimes proclaiming the necessity of relying on such practice while on other occasions failing even to acknowledge the existence of practice contrary to the result it reaches. This behavior by the Court is problematic for a number of reasons and, paradoxically, makes the Court itself an impediment to wider reliance on international law.

Keywords: International Court of Justice, state practice, customary international law, treaties

Suggested Citation

Weisburd, Arthur Mark, The International Court of Justice and the Concept of State Practice. UNC Legal Studies Research Paper No. 1282684, Available at SSRN: or

Arthur Mark Weisburd (Contact Author)

University of North Carolina School of Law ( email )

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