The ensign of the United States is the flag of the United States when worn as an ensign (a type of maritime flag identifying nationality, usually flown from the stern of a ship or boat, or from an installation or facility of the United States Navy, United States Marine Corps, United States Coast Guard or the National Oceanographic and Atmospheric Administration ashore). International maritime law—see International Treaty on Law of the Sea, articles 91 and 92—provides that vessels have a "national character" and thus should display a flag (ensign) that corresponds to this national character, especially when in international or foreign waters. Vessels that are formally documented under the federal vessel documentation act, vessels owned by government bodies in the United States, and vessels