The Commonwealth employes listed in section 5301(a)(1)-(11) of the code (relating to mandatory and optional membership) shall have the option to elect membership or nonmembership in the System. The election of membership or nonmembership is irrevocable and shall be final and binding in the absence of an interruption to Commonwealth service. The election shall be made within 30 days of the effective date of employment.
4 Pa. Code § 243.1