Mo. Rev. Stat. § 388.645: Termination of appointment, procedure.

When a railroad no longer requires the services of a policeman so appointed, it shall file a notice of termination of employment with the director of the department of public safety, or at any time the director of the department of public safety may revoke the appointment by giving notice to the railroad and to the railroad policeman. Thereupon, the powers of such policeman shall cease.