Maryland Code, Corporations and Associations § 5-109

(1) An individual who is authorized by law in this or another state to render a professional service named in the corporation's articles of incorporation;

(2) A general partnership in which all the partners are qualified persons with respect to the professional corporation and in which at least one partner is authorized by law in this State to render a professional service named in the corporation's articles of incorporation; and

(3) A professional corporation, domestic or foreign, provided that the professional corporation receiving the stock is organized to perform the same professional service as the professional corporation issuing the stock.

(b)(1) If a licensing unit with jurisdiction over a profession considers it necessary to prevent a violation of the ethical standards of the profession, the unit may, by regulation, restrict or condition, or revoke in part, the authority of a professional corporation to issue stock subject to its jurisdiction.

(2) A regulation adopted under this subsection does not, of itself, make a stockholder of a professional corporation a disqualified person at the time the regulation becomes effective.