A rule in major IMO conventions that, when inspecting a ship flying the flag of a State which is not a party to the Convention, Port State Control Officers must ensure that the treatment of such a ship and its crew is not more favourable than that of a ship flying the flag of a State party to that Convention. For example, many States have not yet ratified or acceded to MARPOL Annex VI, but ships flying their flags will still be required to meet the requirements of Annex VI to pass port State control inspections.
