Quarantine with a disinfecting stove, have a right to navigate the Canal, in quarantine, subject only to the landing of those who were suffering from plague. Plain yellow, green, and even black flags have been used to symbolize disease in both ships and ports, with the color yellow having a longer historical precedent, as a color of marking for houses of infection, previous to its use as a maritime marking color for disease. The present flag used for the purpose is the "Lima" (L) flag, which is a mixture of yellow and black flags previously used. It is sometimes called the
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