Mich. Comp. Laws § 462.389

Sec. 389. When a company terminates the services of a railroad police officer, it shall file a notice to that effect with the director of the department of state police, stating the date on which services shall be discontinued. The commission issued to the railroad police officer shall become null and void on the date specified. The dismissal of a railroad police officer from employment of the company shall render the commission null and void. The director, on 5 days' notice to the company for whom a railroad police officer was appointed, may revoke a commission issued to the railroad police officer.