Letter of Marque
A Letter of Marque was a government license authorizing a person (known as a privateer) to attack and capture enemy vessels and bring them before admiralty courts for condemnation and sale. Since the war between Arcland and its neighbors has ended, all existing letters of marque have been rescinded, and privateering has halted.
In general, these letters were authorized by governors of Gardish and Lasani colonies, authorizing the capture of Arcish or pirate ships. Attacking a ship, even an enemy ship, without such a letter is considered an act of piracy, and is punishable by death.
It should be noted that Arcland has never recognized Letters of Marque, and would usually hang captured privateers as pirates. (On occasion, Arcish governors would instead ransom captured privateers in exchange for large sums of gold.) Letters of Marque were never valid in the Old World; having been is exclusive to the Bocan Islands.
A Letter of Marque usually specified either a single individual representing a privateering company, or else name the privateering company itself. In either case, a single Letter represented the right to operate a single privateering ship; any captured ships needed be brought back to port and sold at an admiralty court. It was a common practice for these courts to offer less than the market value of a ship, but they would also usually permit a company which has captured a superior vessel to keep it, and sell its old ship instead.
Bearers of a Letter of Marque could still be prosecuted in their home countries if they should attack a non-enemy vessel. A common practice for privateers who could not find enough prey is to attack friendly shipping, and then later claim to have seen an enemy flag flying from its mast. When it proven, this practice was almost always punished by death.
The Imperial Commission (in Gard) or Royal Commission (in Lasant) was similar to a Letter of Marque, except that it authorized a privateering company to maintain and operate a number of ships simultaneously, often with limits between 5 and 10 vessels. Unlike the Letter of Marque, colonial governors were not empowered to grant these commissions. Only a high admiral in the Old World had that authority.
Imperial (or Royal) Commissions were handed out very sparsely, and only to groups which had proven their ability and loyalty. The general understanding was that privateers under Commission are more independent, and consequently at greater risk of infighting or becoming pirates.