40 ILCS 5/12-136

The following described spouses and former spouses of employees shall not have any right to a surviving spouse's annuity from the fund: (a) the spouse of an employee who withdraws or retires and who dies while out of service, if such spouse was not the spouse of the employee while in service; (b) the spouse of an employee who received a refund; (c) the spouse of an employee who dies after withdrawal if the employee withdrew before attainment of age 60 and has less than 10 years of service; (d) the spouse of an employee or annuitant who remarries after the death of the employee or annuitant, if the spouse is under age 55 at the time of the remarriage; (e) the former spouse of any employee, inactive member or annuitant, regardless of the date on which the marriage is dissolved. A spouse's annuity shall terminate upon remarriage while under age 55. Such termination shall be permanent and shall not be affected by any future change in marital status.