Indiana has a "Blacklisting law" which permits employers to disclose only truthful facts about an employee's termination. If you believe your former employee has made untrue statements about you, you must request copies of any written correspondence from a former employer to a potential employer within 30 days of applying for a job with a potential employer. The Indiana Department of Labor has no jurisdiction to investigate such claims. DOL suggests you consult a private attorney about possible legal action that could be taken.
Indiana Department of Labor, 317-232-2655