Letter of Marque (Historic)

A letter of marque was a commission issued by a sovereign authorizing a private vessel owner (a privateer) to attack and capture enemy merchant shipping in wartime and to bring the prizes before a prize court for condemnation. The instrument turned what would otherwise be piracy into a lawful act of war by clothing the private captor with state authority. The 1856 Declaration of Paris abolished privateering among its signatories (its first principle: privateering is and remains abolished); the United States did not accede, and the US Constitution still empowers Congress to grant letters of marque and reprisal (Article I, Section 8).