Md. Code, Public Safety § 5–103

This subtitle does not affect:

(1) a sale or transfer for bona fide resale of a regulated firearm in the ordinary course of business of a licensee; or

(2) a sale, rental, transfer, or the use of a regulated firearm by a person authorized or required to do so as part of the person’s duties as a member of:

(i) an official police force or other law enforcement agency;

(ii) the armed forces, including all official reserve organizations; or

(iii) the Maryland National Guard.