Section 23583 - Membership(a) Membership shall be mandatory for all full-time employees on the effective date of this act and following a 90-day probationary period for all new full-time employees; except that the following employees shall not be entitled to membership: (1) Employees protected by other pension systems authorized by the laws of this State.(2) Employees who did not exercise an option to elect membership in the fund within the times provided.(3) Any temporary employees who do not have contributions in the fund attributable to former membership in the fund.(4) Pensioners who were receiving full retirement benefits and returned to service subsequent to January 1, 1975.(b) Membership shall be mandatory for a temporary employee who was formerly a full-time employee and who has not withdrawn his accumulated contributions from the fund.(c) Membership may continue for any employee on an approved leave of absence for a period of up to two years during which he makes the required contributions.(d) Membership shall continue for an employee who has terminated service after eight or more years of credited service, attained age 40, has elected to leave his contributions in the fund, and continues to contribute to the fund until attainment of age 50.(e) Membership and all rights to benefits provided by this act shall cease at the time an employee terminates city service and withdraws his accumulated contributions. 1975, Aug. 1, P.L. 169, No. 87, § 3, effective Jan. 1, 1975.