Unfortunately, there is no recourse against someone doing something legal, even if it causes you problems or prevents you from getting employment. For example, there is no law which prevents someone from contacting another person, to tell them something truthful about a third person, even if that disclosure or information hurts the third person. If the former employer is lying about something--making a factual statement that is untrue--that would be different; that might be defamation and you might have a cause of action. But if the former employer is telling the unvarnished truth, there is probably nothing you can do, unfortunately. You may need to consider a different industry or relocating, since you can't stop someone from talking if they're just telling the truth.