The areas in Cornwall, where tin was extracted, were known as Stannaries and the law that affected them were known as Stannary Law. These Cornish Stannaries form part of the Duchy of Cornwall, an estate which was created by Edward III in 1337 when he granted his son, Edward, the Black Prince Duke of Cornwall.
The writ appointing the Lord Warden covered the
"just and ancient customs and liberties of miners, smelters and merchants of tin."
The first to hold this title was William de Wrotham who was given this title on the 20th November 1197 during the reign of King Richard I. In 1198, juries of miners at Launceston, stood before Wrotham to swear by the law and practice of the tin mines.
Over the years, Royal Charters issued by Edward I in 1305, Edward IV in 1466, and Henry VII in 1508 have changed and
added to the laws within the Stannaries. King John, often seen as a selfish and greedy king, was not slow to see the attraction of the Cornish tin industry. In 1201 he issued the first charter to the Stannaries. By 1214, production of tin had risen to six hundred tons, the result of this saw many men, who once worked on the land, move to mining. One of the clauses of Magna Carta was that no lord shoud lose the service of his men whether he dug tin or not. Henry III confired his fathers charter, and
the Stannaries soon had their own taxation, no acknowledged lord and were 'a law unto themselves.' By the end of the 13th century the Stannaries were under the control of Richard, the second son of King John and his son Edmund as the Earls of Cornwall.