In 1999, for example, an attaché of the Russian Embassy in Washington DC was declared persona non grata for suspected "bugging" of the State Department.
The UN Convention on the Prevention and Punishment of Crimes against Internationally Protected Persons, Including Diplomatic Agents was adopted in 1973.
It provides that states parties must make attacks upon diplomats a crime in internal law, and obliges them to extradite or prosecute offenders.
Such official communication is inviolable and may include the use of diplomatic couriers and messages in code and in cipher, although the consent of the receiving state is required for a wireless transmitter.
[9] Similarly, the receiving state may at any time declare any member of the diplomatic mission persona non grata and thus obtain the removal of that person.
The International Court of Justice has emphasised that in the absence of treaty or customary rules to the contrary, a decision by a mission to grant asylum involves a derogation from the sovereignty of the receiving state.