A privateer was a pirate who by commission or letter of marque from the government was authorized to seize or destroy a merchant vessel of another nation. The privateer was used as a cheap means of weakening the enemy by frequenting shipping routes (avoiding the costs related to the maintenance and creation of a navy). In theory no Privateer with a letter of marque could be charged with piracy, since it was recognized by international law. However, it was not uncommon for privateers to be charged and prosecuted for piracy by hostile nations. All occurrences of vessels captured by privateers had to be brought before an Admiralty Court where they were tried to ensure that their plunder was legal game.