After the recent situations with CM Punk and Alberto Del Rio, WWE has put in all performer contracts a stipulation that states if they are fired for disciplinary reasons, they forfeit all merchandise rights and they can’t work in either pro wrestling or mixed-martial-arts for a full year.
It’s believed that such a stipulation would not hold up in court, however it would take a lot of money and resources to challenge it and find out, and most talents are that well off to take that kind of chance.
(Credit: Wrestling Observer Newsletter)