Vienna Convention on Treaty Law, an international agreement on treaties of states, drawn up by the UN Commission on International Law and adopted on 23 May 1969 and entered into force on 27 January 1980. Thirty-five UN member states had to ratify the treaty before it could enter into force. Although it was not until 1979 that these ratifications were concluded, more than half of the UN members had approved the convention until early 2018. Even members who had not ratified the document, such as the United States, generally followed the provisions of the agreement. The agreement applies only to written contracts between states. The first part of the document defines the terms and scope of the agreement. The second part sets out the rules governing the conclusion and adoption of contracts, including the agreement of contracting parties and the formulation of reservations, i.e. the refusal to be bound by one or more specific provisions of a contract, while they accept the rest. The third part deals with the application and interpretation of contracts and the fourth part examines the possibilities of amending or amending contracts. These parts essentially codify existing customary law. The most important part of the agreement, Part V, sets out the reasons and rules governing the non-publication, termination or suspension of contracts and contains a provision that gives the International Court of Justice jurisdiction over disputes arising from the application of these provisions. The last parties discuss the impact on treaties on changes in government within a state, changes in consular relations between states and the outbreak of hostilities between states, as well as rules on custodians, registration and ratification.
In addition, there are 12 international organizations that have issued formal confirmations of the convention: IAEA, ICAO, Interpol, ILO, OMI, OPCW, CTBTO Preparatory Commission, UN, UNIDO, UPU, WHO, WIPO. The Vienna Convention on Treaty Law (VCLT) is a treatise on international law on inter-state treaties. It was adopted on May 22, 1969 and was inaugurated at the signing on May 23, 1969.  The convention came into force on January 27, 1980.  Since January 2018, 116 States Parties have ratified the Convention and 15 other states have signed it but have not ratified it.  In addition, the Republic of China (Taiwan), which is currently recognized by only 14 UN member states, signed the 1970 Convention, prior to the UN General Assembly vote, to transfer China`s seat to the People`s Republic of China (PRC).