Unless you have a written employment contract which guarantees you employment, you are an employee at will and may therefore be terminated at any time, for any reason, including refusin to sign a waiver or even just annoying a supervisor; employees at will have no rights to their jobs and can lose them at any time. If unsure what your contract says, it is safer to assume it does *not* protect you from termination, since very, very few people have written employment contracts which prevent their termination.