I always wonder about the contract between the PL and the club when the "City signed up to it" argument rears it's head. City became a shareholder in the PL (and a subscriber to it's then rules) when it was formed, lost its share when we were relegated, and regained it's share in 2001. When the FFP rules were introduced we were an established member and have remained so ever since.
As far as I'm concerned, the PL has a monopoly on the football industry at the top level so any business already operating at the top level of the industry has never had any option but to be a member of the PL in order to practice it's business.
The alternative, as it seems to me, is to "voluntarily" drop down a division and become a member of the Football League but be, permanently, denied access to the higher level (and its income streams) or cease trading altogether and all that entails. In short, it seems to me, that any contract between the PL and it's clubs is not one that the clubs have any realistic option but to "sign up to". At the risk of rousing the lawyers on here, that looks "coercive" to me.