The Vienna Convention on Diplomatic Relations of 1961 is an international treaty that defines a framework for diplomatic relations between independent countries. Its aim is to facilitate "the development of friendly relations" among governments through a uniform set of practices and principles; most notably, it codifies the longstanding custom of diplomatic immunity, in which diplomatic missions are granted privileges that enable diplomats to perform their functions without fear of coercion or harassment by the host country. The Vienna Convention is a cornerstone of modern international relations and international law and is almost universally ratified and observed; it is considered one of the most successful legal instruments drafted under the United Nations. History Throughout the history of sovereign states, diplomats have enjoyed a special status. Their function to negotiate agreements between states demands certain special privileges. An envoy from another nation is traditionally treated as a guest, their communications with their home nation treated as confidential, and their freedom from coercion and subjugation by the host nation treated as essential. The first attempt to codify diplomatic immunity into diplomatic law occurred with the Congress of Vienna in 1815. This was followed much later by the Convention regarding Diplomatic Officers (Havana, 1928). The present treaty on the treatment of diplomats was the outcome of a draft by the International Law Commission. The treaty was adopted on 18 April 1961, by the United Nations Conference on Diplomatic Intercourse and Immunities held in Vienna, Austria, and first implemented on 24 April 1964. The same Conference also adopted the Optional Protocol concerning Acquisition of Nationality, the Optional Protocol concerning the Compulsory Settlement of Disputes, the Final Act and four resolutions annexed to that Act. One notable aspect which arose from the 1961 treaty was the establishment of the Holy See's diplomatic immunity status with other nations. Two years later, the United Nations adopted a closely related treaty, the Vienna Convention on Consular Relations. Summary of provisions The Vienna Convention is an extensive document, containing 53 articles. The following is a basic overview of its key provisions. The host nation at any time and for any reason can declare a particular member of the diplomatic staff to be persona non grata. The sending state must recall this person within a reasonable period of time, or otherwise this person may lose their diplomatic immunity (Article 9). The premises of a diplomatic mission, diplomatic premiers are the houses