Quote: shinymcshine "What I don't understand, with sporting contracts, is whether there is a differentiation between the players right to resign from their current employer (with a stated notice period) and the clubs hold on that player regarding their player registration.
So perhaps a player can just resign, but a club is unlikely to release their registration until they are either compensated to do so, or the original duration of the player's contract ends.'"
You are more or less correct. Most contracts do have a clear and stipulated resignation period. Six months is usually the maximum considered reasonable, even if no time period is explicitly stated in the contract.
However, if there is no resignation period in the contract, the employee only needs to give statutory notice. This is based in the length of time employed, ranging from one week to twelve weeks. My assumption is that Ryan Brierely didn't have an explicit clause in his contract allowing him to leave, but does not have a contractual notice period and is therefore able simply to give statutory notice, in his case of four weeks.
However, you are right about his registration. Usually, by signing a contract players agree that their registration is held by a certain club for a period of time. They may well resign, but even then they do not "own" their own registration and therefore cannot play for anyone else.