Maryland Code, Transportation § 8-733

(a) Except as otherwise provided by law, an outdoor sign along or near a federal-aid primary highway may be lighted, but is subject to the restrictions specified in this section.

(b) A sign that includes or is lighted by any flashing, intermittent, or moving light is prohibited, unless that sign is giving public service information such as time, date, temperature, weather, or similar information.

(c) A sign that is not effectively shielded so as to prevent its light beams or rays from being directed at any part of the main traveled ways of the federal-aid primary highway is prohibited, if the beams or rays:

(d) A sign may not be lighted in any way that obscures or otherwise interferes with the effectiveness of an official traffic sign, signal, or device.