Md. Code, Alcoholic Beverages and Cannabis § 11–1903

(a) A holder of a Class D beer, wine, and liquor license may sell alcoholic beverages or allow alcoholic beverages to be provided only in a room with at least one plain glass window facing the street.

(b) (1) The window shall enable an individual standing on the ground to observe the interior of the premises when sales of alcoholic beverages are prohibited.

(2) The view afforded by the window may not be obstructed when sales of alcoholic beverages are prohibited.