Letter of Marque: a virtual pirate’s charter; Issued by the British government from the early 1700s to the late 1800s, Letters of Marque were official warrants granted to private parties that worked under strict instruction to search property, seize goods and destroy assets belonging to the country’s enemies or those so reckless and naive as to break the law.
Most commonly, they were used to raid merchant ships of enemy nations. Sir Francis Drake and William Kidd were amongst those that received these commissions, however, Kidd was himself later brought-up on charges of piracy.