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. 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. 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. . 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). When the People`s Republic of China then acceded to the convention, it called the signing of the Republic of China (ROC) “illegal.”  65 UN member states have neither signed nor ratified the convention. A convention on international treaties was one of the first efforts of the Commission on International Law and James Brierly was appointed in 1949 as Special Rapporteur to deal with this issue. After his resignation in 1952, each of his successors resorted to the work. Sir Humphrey Waldock, appointed in 1961, drew up six reports from which the Commission was able to draw up a draft which, in 1966, was to be submitted to the United Nations General Assembly, with the recommendation to convene a conference to conclude a convention on the basis of the draft. The conference had its first session in 1968 and the convention was adopted at its second session the following year.
There are 32 States Parties to the Convention to ratify: Mexico, Colombia, Argentina, Uruguay, Senegal, Liberia, Gabon, Australia, United Kingdom, Denmark, Sweden, Estonia, Belarus, Moldova, Bulgaria, Cyprus, Greece, Spain, Germany, Netherlands, Belgium, Switzerland, Liechtenstein, Italy, Croatia, Hungary, Czech Republic, Slovakia, Malta, Albania and Palestine.