Holding affiliates under duress, to agree to T&C's or lose their players, earnings etc., etc., it wouldn't hold water in a court-room. The majority of programs force affiliates over a barrel, because, they figure no one is going to take court action.
The thing is, issues such as these SHOULD be legally challenged.
However after 23 years in this gig, class actions have been raised on the GPWA, AGD and other affiliate forums BUT nothing ever happens. Instead, folks post posts, people b#tch and moan how unfair it all is (which it really is) but that's as far as it goes. No one does jack!
Which sends a clear message to programs that they can bend affiliates over.
Until folks decide enough is enough and actual do something about all this rot, it will continue to repeat itself.