Customary international law is a branch of international law based on the customary norm. The “International Court of Justice, jurists, the United Nations, and its member states” all regard custom as one of the fundamental sources of international law, alongside general principles of law and treaties.
Many states acknowledge the presence of customary international law in theory, while there are conflicting views on what norms it contains.
“Treaties, decisions of national and international courts, national law, views of national legal advisors, diplomatic communication, and practice of international institutions” were mentioned as kinds of proof of CIL by “the International Law Commission” in 1950. The Committee issued “Conclusions on the Identification of Customary International Law,” together with commentary, in 2018. The “United Nations General Assembly” praised the findings and urged them to be widely disseminated.
