It certainly never stop them in the past. In practice they have no money to spare to fight it and a Jury will not be sympathetic. Its like breaking the law and then accuse the accuser of breaking another law.
You can sue them and try to collect damages, but at the very least, you can report them to the Federal Trade Commission, and optionally: the Attorney General in your state.
Both can (and have) take action against the collection agency "in the public interest".