Often referred to as the Manx Magna Charta - this is the Act of Tynwald, agreed to by the last Stanley Lord of Man, in which the Manx farmers, technically tenants of the Lord, gained the right to possess and 'alienate' (i.e. sell, give or will) their land. It ended a century of discontent formed by the Seventh Earl's attempt to force a feudal land-holding scheme alien to the native Manx.
The agent behind this necessary reform was Bishop Wilson, and according to Spenser Walpole (see Chap 12 of Land of Home Rule) was the main act by which he should be remembered.
The background to the act is magisterally put by A.W.Moore in Book 7 of his History of the Isle of Man.