Mo. Rev. Stat. § 115.059: Peace officers to assist election authority or election officials, when requested.

It shall be the duty of the police, the sheriff and all other peace officers to give any assistance or protection required by the election authority, any employee of the election authority, any election judge, any registration officer or any canvasser in the performance of his duties and to comply with all lawful requests and directions of the election authority relating to such assistance.