‘Codification by Interpretation’: The International Law Commission as an Interpreter of International Law

Abstract This article argues that the International Law Commission (ILC) interprets international law. In recent years, in documents intended to remain non-binding, the Commission has made interpretative pronouncements about a treaty in force, the Vienna Convention on the Law of Treaties, and customary international law reflected therein. This development is called the ‘codification by interpretation’ paradigm in this article. This article argues that interpretation falls within the ILC’s function, and it analyses the effects of the Commission’s interpretative pronouncements. It explains that the ILC’s interpretative pronouncements are not per se binding or authentic. However, they may trigger an interpretative dialogue with states. The ILC’s interpretative pronouncements may constitute a focal point for coordination among states, a subsidiary means for determining rules of law and a supplementary means of (treaty) interpretation. The aim of the ILC’s ‘codification-by-interpretation’ paradigm in the four topics considered in this article is to introduce clarity and predictability into secondary rules on the law of treaties, thus ensuring the clarity and predictability of primary treaty rules across all fields of international law. The ILC endeavours to convince states to use international law as a medium by which they regulate their affairs.