Lettre de Marque

In the Age of Sail, a letter of marque and reprisal, or, simply a letter of marque (in France, a lettre de marque or sometimes a lettre de course) was a government license that authorized a person, known as a privateer, to attack and capture enemy vessels. Once captured, the privateer could then bring the case of that prize before their own admiralty court for condemnation and transfer of ownership to the privateer. A letter of marque and reprisal would include permission to cross an international border to effect a reprisal (take some action against an attack or injury) and was authorized by an issuing jurisdiction to conduct reprisal operations outside its borders.

At that time, cruising for enemy prizes with a letter of marque was considered an honorable calling that combined patriotism and profit. Such privateering contrasted with attacks and captures of random ships, which was unlicensed and known as piracy; piracy was almost universally reviled.

In addition to the meaning of the license itself, the terms letter of marque and privateer were sometimes used to describe the vessels used to pursue and capture prizes. In this context, a letter of marque was a lumbering, square-rigged cargo carrier that might pick up a prize if the opportunity arose in its normal course of duties. In contrast, the term privateer generally referred to a fast and weatherly fore-and-aft rigged vessel, heavily armed and heavily crewed, intended exclusively for fighting.

Marque derives from the Old English mearc, which is from the Germanic *mark-, which means boundary, or boundary marker, which is derived from the Proto-Indo-European root *merǵ-, meaning boundary, or border. The French marque is from the Provençal language marca, which is from marcar, also Provençal, meaning, seize as a pledge.

According to the Oxford English Dictionary, the first recorded use of "letters of marque and reprisal" was in an English statute in 1354 during the reign of Edward III. The phrase referred to "a licen[c]e granted by a sovereign to a subject, authorizing him to make reprisals on the subjects of a hostile state for injuries alleged to have been done to him by the enemy's army."

...
Wikipedia