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. Throughout the history of sovereign states, diplomats have enjoyed special status. Their function of negotiating agreements between states requires certain special privileges. An emissary from another nation is traditionally treated as a guest, his communication with his homeland is considered confidential and his freedom of coercion and submission by the host country is considered essential. In the year the treaty was adopted, two amending protocols were added. Countries can ratify the main treaty without necessarily ratifying these optional agreements. 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 contracts concluded after its creation and to contracts between states and therefore does not regulate agreements between states and international organizations or between international organisations themselves, but if one of their rules is binding on these organisations, they will remain so.
 The VCLT applies to interstate contracts within an intergovernmental organization.  The Vienna Convention on Treaty Law (VCLT) is an international agreement governing treaties between states.  The contract, known as the “contract,” contains detailed rules, procedures and guidelines for the definition, development, modification, interpretation and general operation of contracts.  The VCLT is considered to be the codification of customary international law and state contract practice.  The rules for the assumption of foreign emissaries have been developed for millennia by leaders and governments who wanted their representatives to return in one piece. Initially, they were agreed on a bilateral or small-group basis. It was not until the Congress of Vienna in 1815 that they began to be codified as international law. This first set of rules dealt with what governments considered to be the most pressing issue: the hierarchy between ambassadors and envoys. The short-lived League of Nations extended the extension of the rules to diplomatic privileges and immunities, but in 1927 efforts were not considered important enough for persecution.