Maryland Code, Public Safety § 11-105

(b)(1) A person shall obtain a license to engage in business as a dealer under this subtitle before the person engages in the business of loading or reloading small arms ammunition in the State.

(2) The owner or operator of a mine, quarry, or other operation or business that uses explosives, or a contractor who performs work that uses explosives, shall obtain a license to engage in business as a dealer under this subtitle.

(d)(1) Subject to paragraph (2) of this subsection, a person need not obtain a license to possess or store up to 5 pounds of smokeless powder for the loading or reloading of small arms ammunition, and up to 5 pounds of black powder for the loading or reloading of small arms ammunition or for use in the loading of antique arms or replicas of antique arms, if the smokeless powder and black powder are stored in their original shipping containers and are possessed only for personal use in firearms.

(2) A person may not possess or store explosives for use in firearms in any quantity in multifamily dwellings, apartments, dormitories, hotels, schools, other public buildings, or buildings or structures open for public use.

(3) Notwithstanding paragraph (2) of this subsection, the State Fire Marshal may issue a permit to allow temporary possession of explosives for use in firearms in a building or structure open for public use.