Md. Code, Election Law § 10–304

(a) (1) A police officer who is on duty at a polling place shall obey the order of an election judge for that polling place.

(2) A police officer making an arrest under an order of an election judge is fully protected in so doing as if the police officer received a valid warrant to make the arrest.

(b) A police officer who is on duty at a polling place shall protect a challenger or watcher in the discharge of the duties of the challenger or watcher.