Md. Code, State Personnel and Pensions § 31-111

(a) Except as provided in subsection (b) of this section and §§ 31–111.1, 31–111.3, 31–111.4, 31–111.5, 31–111.6, 31–111.7, and 31–111.8 of this subtitle, if an employee of a participating governmental unit joins the Employees’ Pension System on the effective date, the employee is entitled to service credit for employment with the participating governmental unit before the effective date.

(b) If an employee of the Baltimore Metropolitan Council elects to become a member of the Employees’ Retirement System or the Employees’ Pension System, the employee may not receive credit for service from July 1, 1992, to the effective date unless the employee pays to the Board of Trustees the amount of the member contributions the employee would have made during that period, plus regular interest.