Inviolability of Official Correspondence

… 2. The official correspondence of the mission shall be inviolable. Official correspondence means all correspondence relating to the mission and its functions. … There was no clearly established rule of customary international law according inviolability to correspondence to or from a diplomatic mission which was sent through the public postal facilities. Letters to a mission would become archives or documents of the mission on delivery, but not before. Letters from a mission were not in practice sent through the ordinary post if they were of any importance or...