The Vienna Convention on the Law of Treaties codified the rules on treaties and wrote jus cogens into positive international law

Background

The Vienna Convention on the Law of Treaties was adopted at Vienna on 23 May 1969 by the United Nations Conference on the Law of Treaties, and it has been in force since 27 January 1980. The General Assembly convened that conference by resolution 2166 (XXI), working from a final draft of the International Law Commission whose last Special Rapporteur was Sir Humphrey Waldock. The Convention applies to written treaties between States, excluding treaties concluded by international organizations; a separate convention of 1986 covers those. It prohibits reservations that are incompatible with the object and purpose of the treaty to which they relate, in article 19 (c). Its rule of interpretation makes the object and purpose of a treaty, and its context, guidelines for reading the text. Articles 53 and 64 introduced the concept of jus cogens, a peremptory norm of international law, into positive international law. The conference accepted the final text by 79 votes to 1, with 19 abstentions.