Md. Code, State Government § 22-201

(a) Employees of a public employer have the right to:

(1) engage in concerted activities for the purposes of mutual aid or protection; and

(2) refrain from any or all activities described under item (1) of this subsection.

(b) Public employees have the right to:

(1) form, join and participate in, or to refrain from forming, joining, or participating in, any employee organization of their own choosing;

(2) be represented by employee organizations, to negotiate collectively with their public employers in the determination of their terms and conditions of employment, and the administration of grievances arising thereunder; and

(3) be fairly represented by their exclusive representative, if any, in collective bargaining.

(c) Except as provided in subsection (d) of this section, an employee organization may establish reasonable:

(1) restrictions as to who may join; and

(2) provisions for the dismissal of individuals from membership.

(d) An employee organization may not establish restrictions and provisions under subsection (c) of this section that discriminate with regard to the terms or conditions of membership because of:

(1) age;

(2) ancestry;

(3) color;

(4) creed;

(5) gender identity;

(6) marital status;

(7) mental or physical disability;

(8) national origin;

(9) race;

(10) religious affiliation, belief, or opinion;

(11) sex; or

(12) sexual orientation.