Prize Law.....................................

From Wikipedia:

"Prize is a term used in admiralty law to refer to equipment, vehicles, vessels, and cargo captured during armed conflict. The most common use of prize in this sense is the capture of an enemy ship and its cargo as a prize of war. In the past, the capturing force would commonly be allotted a share of the worth of the captured prize. Nations often granted letters of marque that would entitle private parties to capture enemy property, usually ships. Once the ship was secured on friendly territory, it would be made the subject of a prize case, an in rem proceeding in which the court determined the status of the condemned property and the manner in which it was to be disposed of."

"Fortunes in prize money were to be made at sea as vividly depicted in the novels of C. S. Forester and Patrick O'Brian. During the American Revolution the combined American naval and privateering prizes totaled nearly $24 million;^[7] in the War of 1812, $45 million.^[8] Such huge revenues were earned when $200 were a generous year's wages for a sailor;^[9] his share of a single prize could fetch ten or twenty times his yearly pay, and taking five or six prizes in one voyage was common. With so much at stake prize law attracted some of the greatest legal talent of the age, including John Adams, Joseph Story, Daniel Websterand Richard Henry Dana, Jr. author of Two Years Before the Mast."

Your humble servant could not (after a totally brief search) find an 1808 British statute concerning prizes.  Perhaps O'Brian was just exercising his artistic license as a writer.