What is "letters of marque and reprisal"

Marque \Marque\, n. [F. marque, in lettre de marque letter of marque, a commission with which the commandant of every armed vessel was obliged to be provided, under penalty of being considered a pirate or corsair; marque here prob. meaning, border, boundary (the letter of marque being a permission to go beyond the border), and of German origin. See March border.] (Law) A license to pass the limits of a jurisdiction, or boundary of a country, for the purpose of making reprisals.

Letters of marque, Letters of marque and reprisal, a license or extraordinary commission granted by a government to a private person to fit out a privateer or armed ship to cruise at sea and make prize of the enemy's ships and merchandise. The ship so commissioned is sometimes called a letter of marque.

Reprisal \Re*pris"al\ (r?-priz"al), n. [F. repr?saille, It. ripresaglia, rappresaglia, LL. reprensaliae, fr. L. reprehendere, reprehensum. See Reprehend, Reprise.]

1. The act of taking from an enemy by way of reteliation or indemnity.

   Debatable ground, on which incursions and reprisals continued to take place.
   --Macaulay.

2. Anything taken from an enemy in retaliation.

3. The act of retorting on an enemy by inflicting suffering or death on a prisoner taken from him, in retaliation for an act of inhumanity.
   --Vattel (Trans.)

4. Any act of retaliation.
   --Waterland.

   Letters of marque and reprisal. See under Marque.