THE RELATIONSHIP BETWEEN INTERNATIONAL TREATIES AND CUSTOMARY INTERNATIONAL LAW

Аннотация

This study examines the dynamic and complex relationship between international treaties and customary international law (CIL), the two primary sources of international obligations articulated in Article 38(1) of the Statute of the International Court of Justice. Historically conceptualized as separate and autonomous sources, modern international legal jurisprudence increasingly demonstrates that treaties and custom operate within a symbiotic, mutually reinforcing framework. Utilizing the triadic typology established by the International Court of Justice in landmark jurisprudence—most notably the North Sea Continental Shelf cases—this paper analyzes how treaties codify pre-existing customary rules, crystallize emerging norms during negotiations, and generate new customary rules subsequent to their adoption. The inquiry explores how codification treaties clarify unwritten customary obligations while simultaneously risking normative fragmentation or ossification. Furthermore, it addresses critical theoretical friction points, including the persistent objector doctrine, the status of non-parties to treaties, and the hierarchical dynamics introduced by peremptory norms (jus cogens). By evaluating state practice, opinio juris, and judicial interpretations across key areas such as human rights law, international humanitarian law, and the law of the sea, this paper demonstrates that treaties and customary international law do not operate in isolation. Instead, they constitute an integrated normative dialogue that preserves the stability, adaptability, and universality of the international legal order.