University of Tehran Public Law Studies Quarterly 2423-8120 52 1 2022 03 21 The Role of Subsequent Practice in the Interpretation of Constituent Treaties of International Organizations The Role of Subsequent Practice in the Interpretation of Constituent Treaties of International Organizations 1 23 85679 10.22059/jplsq.2018.251597.1665 FA Abassali Kadkhodaei Prof., Public Law Department, Faculty of Law and Political Sciences, University of Tehran, Tehran, Iran Ehsan Shahsavari Assistant Prof., Department of Law, Faculty of Law and Political Science, University of Mazandaran, Babolsar, Iran Journal Article 2018 01 31 Under Articles 31 and 32 of the 1969  and 1986 Vienna Conventions on the Law of Treaties, subsequent practice in the application of the treaty is an authentic element in the interpretation of that treaty. The constituent treaty of an international organization is the legal basis under which that organization operates. The growth and development of an international organization and its proper functioning, requires a better understanding of its constituent treaty in light of subsequent practice. It is believed that the subsequent practice of parties to the constituent treaty, the subsequent practice of the organization’s organs and a combination of both can be used for elucidating the content of the constituent treaty. Articles 12(1) and 27(3) of the Charter of the United Nations are representative examples. International jurisprudence, findings of the International Law Commission, and legal scholarship confirm the role of subsequent practice in interpreting the UN Charter. Under Articles 31 and 32 of the 1969  and 1986 Vienna Conventions on the Law of Treaties, subsequent practice in the application of the treaty is an authentic element in the interpretation of that treaty. The constituent treaty of an international organization is the legal basis under which that organization operates. The growth and development of an international organization and its proper functioning, requires a better understanding of its constituent treaty in light of subsequent practice. It is believed that the subsequent practice of parties to the constituent treaty, the subsequent practice of the organization’s organs and a combination of both can be used for elucidating the content of the constituent treaty. Articles 12(1) and 27(3) of the Charter of the United Nations are representative examples. International jurisprudence, findings of the International Law Commission, and legal scholarship confirm the role of subsequent practice in interpreting the UN Charter. https://jplsq.ut.ac.ir/article_85679_25ac680c00219879d6e12e4ac6b18c53.pdf