The Coast Guard ensign on the Coast Guard flag  serves as the seagoing equivalent of a policeman's badge, the distinctive sign of a Coast Guard vessel's law enforcement authority. It derives from the "revenue ensign" adopted on August 1st, 1799, by Secretary of the Treasury Oliver Wolcott, with the approval of President John Adams, to identify the cutters of the Revenue Marine, the principal predecessor of the modern Coast Guard.  On March 2nd of that year, Congress had enacted the Customs Administration Act, providing in part that "the cutters and boats employed in the service of the revenue shall be distinguished from other vessels by an ensign and pendant, with such marks thereon as shall be prescribed by the President."  The law, and the adoption of the distinctive flag, was inspired by ship-owners' concerns that a ship claiming to be a revenue cutter and ordering a merchant vessel to heave to might actually be a pirate.