Md. Code, Public Safety § 13–212

A member of the organized militia, including the member’s conveyance and military property, shall be allowed free passage through any toll gate and over any toll road, bridge, or ferry if the member:

(1) is traveling to or returning from a parade, encampment, drill, or other duty that the member may be required by law to attend; and

(2) presents an order for duty or identification card.