University of Tehran Public Law Studies Quarterly 2423-8120 Articles in Press 2026 11 22 Interpretation of Customary International Law: From its Existence to Functionality Interpretation of Customary International Law: From its Existence to Functionality 1 24 106777 10.22059/jplsq.2024.379337.3566 FA Abasali Kadkhodaee Prof., Departement of Public Law, Faculty of Law and Political Science, University of Tehran, Tehran, Iran Seyed Hossein Sadat Meidani Assistant Prof., Department of International Law, School of International Relations Ministry of Foreign Affairs, Tehran, Iran Kasra Pourmikaeil Ph.D. Candidate in International Law, Faculty of Law and Political Science, University of Tehran, Tehran, Iran Journal Article 2024 07 26 It is a fact that international law does not contain any general prescriptions regarding interpretation. While some interpretative principles and rules have become reference points, international law does not require a unified interpretation process for all sources of international law, and rules of interpretation may vary based on the source of law. This article sheds light on these applicable rules that can be used when interpreting customary rules, arguing that the interpretation process is an entirely separate operation from identification and both play their particular role in the life cycle of customary rules. However, due to its fluidity and unwritten nature, applying interpretative approaches and elements to customary rules requires its formulation compared to treaty law. This article argues that contextual interpretation is the appropriate approach to interpreting CIL. Contextualism is not only an overarching principle in identifying CIL but also a proper method for interpreting it.  Subsequent practice and other relevant rules of international law are also pertinent elements that could be applied in interpreting customary rules. It is a fact that international law does not contain any general prescriptions regarding interpretation. While some interpretative principles and rules have become reference points, international law does not require a unified interpretation process for all sources of international law, and rules of interpretation may vary based on the source of law. This article sheds light on these applicable rules that can be used when interpreting customary rules, arguing that the interpretation process is an entirely separate operation from identification and both play their particular role in the life cycle of customary rules. However, due to its fluidity and unwritten nature, applying interpretative approaches and elements to customary rules requires its formulation compared to treaty law. This article argues that contextual interpretation is the appropriate approach to interpreting CIL. Contextualism is not only an overarching principle in identifying CIL but also a proper method for interpreting it.  Subsequent practice and other relevant rules of international law are also pertinent elements that could be applied in interpreting customary rules. https://jplsq.ut.ac.ir/article_106777_6bedc138481d6076948bf0d3098ffabf.pdf