40 ILCS 5/18-161
Except as provided in this Article, all moneys in the fund created by this Article, and all securities and other property of the System, and all annuities and other benefits payable under this Article, and all accumulated contributions and other credits of participants in this System, and the right of any person to receive an annuity or other benefit under this Article, or a refund or return of contributions, shall not be subject to judgment, execution, garnishment, attachment, or other seizure by process, in bankruptcy or otherwise, nor to sale, pledge, mortgage or other alienation, and shall not be assignable. A person receiving an annuity or benefit, or refund or return of contributions, may authorize withholding from such annuity, benefit, refund or return of contributions in accordance with the provisions of the "State Salary and Annuity Withholding Act", approved August 21, 1961, as now or hereafter amended.
The General Assembly finds and declares that the amendment to this Section made by this amendatory Act of 1989 is a clarification of existing law, and an indication of its previous intent in enacting and amending this Section. Notwithstanding Section 1-103.1, application of this amendment shall not be limited to persons in service on or after the effective date of this amendatory Act of 1989.
40 ILCS 5/18-161