Öz
International organizations are persons of international law. These international legal persons are bound by the rules of customary international law. The contribution of international organizations to the formation of international customary law rules is controversial. Draft Conclusions on Identification of Customary International Law published by the International Law Commission (ILC) in 2018, had a significant impact on these debates. The ILC has regulated that the practices of international organizations can contribute to the formation of international customary law in certain cases. However, there is no provision regarding international organizations at the point of determination of opinio juris. The ILC incorporated international organizations in the formation of international customary law in a limited and ambiguous way. This article examines the effect of international organizations on the formation of international customary law rules with the developments in the doctrine and the approach of the ILC to the subject. Within the framework of its international legal personality, international organizations can conclude international treaties, have international responsibilities and have various privileges and immunities. Therefore, international organizations should be able to contribute to international customary law, in matters related to their field of activity