Md. Code, Commercial Law § 14–1602

(a) A person may not sell at retail or rent, or attempt to sell at retail or rent, a video movie in this State unless the official rating of the motion picture from which it is copied is clearly displayed on the outside of any cassette, case, jacket, or other covering of the video movie.

(b) Subsection (a) of this section does not apply to any video movie of a motion picture which:

(1) Has not been given an official rating; or

(2) Has been altered in any way subsequent to receiving an official rating.