The principle that a nation may exercise jurisdiction over a foreign vessel in one of its ports when activity on board that vessel disturbs the tranquillity of the port. In bilateral treaties, this provides a common exception to the usual rule that cedes primary jurisdiction over vessels to the state of the vessel's nationality. The position of warships, however, is different. Since Chief Justice Marshall in The Schooner Exchange v M'Faddon (1812) 7 Cranch 116 declared that a public armed ship constitutes a part of the military force of the nation, it has been accepted that warships are immune from the jurisdiction of any foreign sovereign. This does not mean that a visiting warship may flout port regulations; if it does so, it may be required to leave port. Nor does it mean that events occurring on board the ship take place outside the jurisdiction of the port state. It merely means that the ship cannot be arrested or taxed and that the local authorities have no competence with respect to crimes committed on board unless the captain surrenders the offender to them. In any respects, the immunity may be waived (Chung Chi Cheung v The King  AC 160 (PC) and in no sense is a ship to be regarded as a territorial enclave.