Thoughts on Domestic Adjudication and the Identification and Formation of Customary International Law

Abstract

Article 38(1)(d) of the ICJ Statute provides that “judicial decisions” may serve as a subsidiary means for the determination of customary international law. The absence of a qualifying adjective to the term “judicial decisions” confirms that, at least ex facie, there is no priority to be given to international over domestic judgments in this respect. And yet – as the International Law Commission’s Draft Conclusions on Formation and Identification of Customary International Law confirms – the reality of international adjudication is one in which domestic judicial decisions are often side-lined. In this paper, I question the ILC’s assertion that this is due to the relative expertise of international versus domestic courts, and instead posit a model based on the shifting architectonics of international adjudication. Two related developments are key: (1) the florescence of international adjudicative bodies in the post-1945 era, and (2) the tendency for international courts and tribunals to see domestic judicial decisions as evidence of state practice and opinio juris under Article 38(1)(b), rather than as subsidiary means for the determination of custom – that is, as factual rather than legal precedents.