Diplomatic immunity is a form of legal immunity and a policy held between governments that ensures that diplomat

Diplomat

A diplomat is a person appointed by a state to conduct diplomacy with another state or international organization. The main functions of diplomats revolve around the representation and protection of the interests and nationals of the sending state, as well as the promotion of information and...

s are given safe passage and are considered not susceptible to lawsuit

Lawsuit

A lawsuit or "suit in law" is a civil action brought in a court of law in which a plaintiff, a party who claims to have incurred loss as a result of a defendant's actions, demands a legal or equitable remedy. The defendant is required to respond to the plaintiff's complaint...

 or prosecution under the host country's laws (although they can be expelled

Deportation

Deportation means the expulsion of a person or group of people from a place or country. Today it often refers to the expulsion of foreign nationals whereas the expulsion of nationals is called banishment, exile, or penal transportation...

). It was agreed as international law

International law

Public international law concerns the structure and conduct of sovereign states; analogous entities, such as the Holy See; and intergovernmental organizations. To a lesser degree, international law also may affect multinational corporations and individuals, an impact increasingly evolving beyond...

 in the Vienna Convention on Diplomatic Relations

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. It specifies the privileges of a diplomatic mission that enable diplomats to perform their function without fear of coercion or...

 (1961), though the concept and custom have a much longer history. Many principles of diplomatic immunity are now considered to be customary law.