Letters of Marque

A Letter of Marque and Reprisal, commonly known as a Letter of Marque, was a warrant or commission from a national government usually authorizing a designated agent to search, seize, or destroy specified assets or personnel belonging to a party which has committed some offense under the laws of that nation.

Usage
James Norrington~1746 to hire him as Admiral of the Naval Fleet

Cadet~ Used in May 1745 to hire him as an EITC agent

Captain Jim Logan~ January 1745 to hired as the Grand Admiral of the British Royal Navy, later resigned.

Captain Hector Barbossa~ 1749 to hire him as Grand Admiral of his Majesty's Navy. later resigned in 1750