(a) Only for the purpose of determining eligibility for benefits accruing under this Article, creditable service standing to the credit of a member of the Legislative Retirement System, Teachers' and State Employees' Retirement System, or the Local Governmental Employees' Retirement System shall be added to the creditable service standing to the credit of a member of this System; provided, that in the event a person is a retired member of any of the foregoing retirement systems, such creditable service standing to the credit of the retired member prior to retirement shall be likewise counted. In no instance shall service credits maintained in the aforementioned retirement systems be added to the creditable service in this System for application of this System's benefit accrual rate in computing a service retirement benefit unless specifically authorized by this Article.
(b) A person who was a former member of this System and who has forfeited his creditable service in this System by receiving a return of contributions and who has creditable service in the Legislative Retirement System, Teachers' and State Employees' Retirement System, or the Local Government Employees' Retirement System may count such creditable service for the purpose of restoring the creditable service forfeited in this System under the terms and conditions as set forth in this Article and reestablish membership in this System.
(c) Creditable service under this section shall not be counted twice for the same period of time whether earned as a member, purchased, or granted as prior service credits. (1989 (Reg. Sess., 1990), c. 1066, s. 35(d); 1997-456, s. 27.)