Quarantine Edinburgh and Leith, grain was from that date declared to be a non-susceptible article. About 1788 an order of the council required every ship liable to quarantine, in case of meeting any vessel at sea, or within four leagues of the coast of Great Britain or Ireland, to hoist a yellow flag in the daytime and show a light at the main topmast head at night, under a penalty of After 1800, ships from plague-countries (or with foul bills) were enabled to perform their quarantine on arrival in the Medway instead of taking a Mediterranean port on the way for
Flag of convenience enforcement by countries when they visit ports in those countries, called port state control. International law requires that every merchant ship be registered in a country. The country in which a ship is registered is its flag state, and the flag state gives the ship the right to fly its civil ensign. A ship operates under the laws of its flag state, and these laws are used if the ship is involved in an admiralty case. A ship's flag state exercises regulatory control over the vessel and is required to inspect it regularly, certify the ship's equipment and crew, and