Vienna Convention on Diplomatic Relations

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.

Source: Wikipedia — Vienna Convention on Diplomatic Relations (CC BY-SA 4.0)