Letter of Marque

The Letter of Marque and reprisal is a government license that was published in the Age of Sail that authorized a private individual, known as a privateer or corsair, to attack and capture vessels of a nation at war with the issuer as under the protection of the issuer (a state or kingdom).
After capturing, the privateers could 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 conduct a reprisal (take some action against an attack or injury) and is authorized by an issuing jurisdiction to conduct reprisal operations outside its borders.