A Theory of Constructive Interpretation for Customary International Law Identification

Abstract

Scholars and judicial practice have long debated the nature of customary international law as a source of international law, including its normative identification. Existing approaches to customary international law identification largely follow the methods of induction and deduction. However, these two methods are two ends of a spectrum and international law has yet to engage systematically with other methodological approaches that lay within this spectrum. This article introduces a mid-spectrum approach by applying the theory of constructive interpretation to customary international law identification. The article introduces the guiding principles of constructive interpretation, examines the process of constructive interpretation in the abstract, and applies it specifically to customary international law identification. The article argues that constructive interpretation carries significant advantages over existing methods of customary international law identification that facilitate the resolution of the main two customary international law impasses: (1) the relationship between general state practice and opinio juris; and (2) opinion juris’ circularity problem. Finally, this article applies constructive interpretation to the judicial assessment of customary international law identification, arguing that the ICJ has already utilized constructive interpretation in reaching parts of its findings in the Nicaragua v. US Case. Through constructive interpretation, international law may escape the methodological divide of induction versus deduction in the process of CIL identification.

Keywords: reflective equilibrium, state practice, opinio juris, use of force, adjudication, ICJ, ronald dworkin, nicaragua case, international legal theory, constructive interpretation, interpretivism, international law, customary international law