The Vienna Convention on the Law of Treaties (VCLT) is a treaty concerning the international law on treaties between states. It was adopted on 22 May 1969 and opened for signature on 23 May 1969. The Convention entered into force on 27 January 1980. The VCLT has been ratified by 114 states as of April 2014. Some countries that have not ratified the Convention, such as the United States, recognize parts of it as a restatement of customary law and binding upon them as such.