International treaties and customary international law are two main sources in the international legal system. Both have the function of regulating relations between countries and international actors, but there are differences in the mechanisms of formation and binding force. This article aims to conduct a comparative study of the binding force between international treaties and customary international law. Using normative legal research methods, an analysis is carried out on the legal principles, doctrines, and practices of states to understand how the legitimacy and effectiveness of both are recognized in the international legal system. The results of the study show that international treaties generally have more explicit and specific binding force because they are based on the formal agreement of the parties, while customary international law is binding based on general practices accepted as law (opinio juris). However, in certain situations, customary law can apply more broadly, including to countries that are not parties to an agreement. This study emphasizes the importance of understanding the interaction between the two in an effort to maintain legal certainty and stability of international relations.
Grace Putri Waghe (Tue,) studied this question.