Determining international custom in modern international law

Abstract

Existing in unwritten form, international custom is one of important sources of international law. That Article 38.1 (b) of Statute of the International Court of Justice (ICJ) prescribes international custom without specific guidance on how to define it leads to difficulties in defining international custom and inconsistencies in application. The International Law Commission of the United Nations has made considerable efforts to clarify how to define international custom and the article aims to analyze the determining factors of international custom according to the United Nations’ guidelines and dispute settlement practices of ICJ.