Is there a law to prevent employers from disclosing information about a termination?

I’ve read that if an employer has legitimate access to employees (or past employees) information, they still needs legitimate reasons to share this information with others. If they does share any information from an employees file to someone that does not have legitimate reasons of knowing this information, it can be a violation of the law. Is disclosing privacy act information to others a violation of law? If so, which law?