Maryland Code, Business Regulation § 10-502

(b)(1) A supplier of motor fuel authorized under this title to supply retail service stations may, at such stations, sponsor, promote, advertise, or otherwise perform or participate in a game of chance if the retail service station dealer agrees to participate in the game of chance.

(2) A supplier of motor fuel authorized under this section to conduct a game of chance may not require a retail service station dealer to participate in the game of chance.