DIPLOMATIC LAW is that area of international law that governs permanent and temporary diplomatic missions. A fundamental concept of diplomatic law is that of diplomatic immunity, which derives from state immunity.
Key elements of diplomatic law are the immunity of diplomatic staff, the inviolability of the diplomatic mission and its grounds, and the security of diplomatic correspondence and diplomatic bags. Famous cases involving the breaking of diplomatic laws includes the Iran hostage crisis in 1979, the shooting of a British police woman (Murder of Yvonne Fletcher) from the Libyan Embassy in London in 1984, and the discovery of a former Nigerian Minister in a diplomatic crate at Stansted airport[1] in 1984.
It is also an accepted principle of customary international law and is recognised between countries as a matter of practicality. Diplomatic law is often strictly adhered to by states because it works on reciprocity. For example, if a country expels diplomats from another country, then its diplomats would most likely be expelled from the other country.