ボスマン判決
A pre-contract is an agreement by a player and an agreeing to take his registration at a later date, and became more well known after the Bosman ruling in 1995. A club may sign a pre-contract with a player while he is still with another club, by which the player agrees to move to the club at a future date, usually after his contract with his current club expires. Under the Bosman ruling, a player can sign a contract with a new club up to six months before his existing contract expires.