46 CFR 26.15-1: -1 May board at any time.

(a) To facilitate the boarding of vessels by the commissioned, warrant, and petty officers of the U.S. Coast Guard in the exercise of their authority, every uninspected vessel, as defined in 46 U.S.C. 2101, if underway and upon being hailed by a Coast Guard vessel, must stop immediately and lay to, or must maneuver in such a way to permit the Coast Guard boarding officer to come aboard. Failure to permit a Coast Guard boarding officer to board a vessel or refusal to comply will subject the operator or owner of the vessel to the penalties provided in law.

(b) Coast Guard boarding vessels will be identified by the display of the Coast Guard ensign as a symbol of authority and the Coast Guard personnel will be dressed in Coast Guard uniform. The Coast Guard boarding officer upon boarding a vessel will identify himself to the master, owner, or operator and explain his mission.