Forcing a contract for what? Responsible for what? Whether pilots sign a contract or not they have to train you if they want you to work there. Even if a new hire had a e170 type rating, he would still have to go through the same course as a new hire who didnt. The answer is simple they need to train you no matter what, this is not something that comes out of the kindness of their hearts.
I guarantee you if nobody ever signed that thing they would still have to hire guys eventually. I can't see something like that holding up in court, just my .02