Anything that could be deemed a restriction of trade will not be allowed.. you can't stop a business making what they can.
Telling one club they can make x amount and another they can make y amount.. won't last a day in court.
Can't do anything when a player is out of contract...plus players decide where they go now.. if a club is trying to stop him making more money then it's not going to end well.
When me and my younger brother was watching wrestling and it came up on the screen that Cole had signed for Man utd...my brother being a man utd fan laughing at me crying got punched in the ear soon after ?