Md. Code, State Personnel and Pensions § 30–302

(a) An election to participate in the program shall be made by an eligible employee at commencement of employment.

(b) An eligible employee’s election to participate in the program is a one–time irrevocable election.

(c) An individual who previously participated in a State system as an employee of an employing institution or any other unit of State government may not elect to participate in the program.