Md. Code, Criminal Law § 12–110

(a) A person who loses money at a gaming device that is prohibited by this subtitle, Subtitle 2 of this title, or Title 13 of this article:

(1) may recover the money as if it were a common debt; and

(2) is a competent witness to prove the loss.

(b) Notwithstanding subsection (a) of this section, a person may not recover money or any other thing that the person won by betting at a gaming device prohibited by this subtitle, Subtitle 2 of this title, or Title 13 of this article.