It may already be a crime for women to be paid less, but is it really enforced? There is plenty of evidence to say otherwise. If anything, making a woman sign a NDA on their pay illegal would provide evidence for both sides (as in, against those who are gaming the system, or for those who've actually been wronged). Making the company front all legal fees is pretty good persuasion to make sure all is equal. In the end it just seems this provides additional pressure and should only worry those are actually guilty of this.