The only thing I've been able to find is the note that since copyright is federal law, state contract law actually can't supersede it, to wit: if you try to put a clause in the contract that says the contract is void if I use your work to make transformative fair-use works (or I owe you a fee), that clause is functionally unenforceable (for the same reason that I don't owe you a fee if I make transformative fair-use works of your creations in general).
The only thing I've been able to find is the note that since copyright is federal law, state contract law actually can't supersede it, to wit: if you try to put a clause in the contract that says the contract is void if I use your work to make transformative fair-use works (or I owe you a fee), that clause is functionally unenforceable (for the same reason that I don't owe you a fee if I make transformative fair-use works of your creations in general).