Md. Code, Public 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.