Maryland Code, Election Law § 16-903

(1) wearing a public or private law enforcement or security guard uniform;

(2) using an armband; or

(3) except as required by law or by regulation adopted by the State Board in connection with ballot security activities, carrying or displaying a gun or badge within 100 feet of a polling site on election day.

(b)(1) A law enforcement officer or security guard who is on duty or traveling to or from duty may vote while wearing a uniform.

(2) A law enforcement officer who is performing an official governmental function may wear a uniform at a polling site.