18 GCA § 56403: Compulsory Pilotage.

On entering or leaving, or operating a vessel within, a port or harbor, the master of a vessel, unless otherwise exempt under the provisions of this Chapter or pursuant to Federal Law, must take on a pilot duly licensed by the Port Authority of Guam to provide pilotage services. While the pilot is on board he shall advise the vessel's master as to its navigation. However, the master of the vessel shall at all times remain in full charge and control of the vessel and its navigation.