Primary and Subsidiary Sources of International Law

Abstract

This study examines the sources of public international law as stipulated in Article 38 of the Statute of the International Court of Justice. It categorizes these sources into primary and supplementary, a framework designed to ensure stable relations among the subjects of the international community and to regulate their respective rights and obligations. Primary sources include international treaties and agreements—the most dynamic instruments for keeping pace with contemporary global shifts and developments—as well as international custom, which arises from consistent state practice coupled with a sense of legal obligation (opinio juris), thereby establishing binding rules of conduct. Also included are the general principles of law, which are well-established in the national legal systems of most nations and serve to prevent legal lacunae (gaps) in the international order. Supplementary or evidentiary sources encompass the jurisprudence of national and international courts, as well as the writings of legal scholars, which assist in the interpretation and resolution of legal provisions. Furthermore, these include the principles of justice and equity, which allow a judge to temper the rigidity of formal legal texts or to address omissions where no specific provision exists. The study demonstrates that the integration of these sources fosters the ongoing development of international law, enabling it to remain responsive to the disputes brought before it. Consequently, this dual classification serves as a legal safeguard for the realization of justice and the stability of international relations within the framework of the United Nations.