10 U.S.C. § 8172
Marine Corps organizations on vessels: authority of officers
When an organization of the Marine Corps is embarked in any vessel, not as part of the authorized complement of the vessel, the authority of the officers of that organization is the same as though the organization were serving at a naval station. However, this section does not impair the paramount authority of the commanding officer of a vessel over the vessel and all persons embarked in it.