Md. Code, Pub. Safety § 5-203

(a) A person may not possess a short–barreled rifle or short–barreled shotgun unless: (1) the person, while on official business is: (i) a member of the law enforcement personnel of the federal government, the State, or a political subdivision of the State; (ii) a member of the armed forces or the National Guard while on duty or traveling to or from duty; (iii) a member of the law enforcement personnel of another state or a political subdivision of another state, while temporarily in this State; (iv) a warden or correctional officer of a correctional facility in the State; or (v) a sheriff or a temporary or full–time deputy sheriff; or (2) the short–barreled shotgun or short–barreled rifle has been registered with the federal government in accordance with federal law. (b) In a prosecution under this section, the defendant has the burden of proving the lawful registration of the short-barreled shotgun or short-barreled rifle. (c) A person who violates this section is guilty of a misdemeanor and on conviction is subject to imprisonment not exceeding 5 years or a fine not exceeding $5,000 or both.