40 ILCS 5/5-159
When a policeman who has withdrawn after the effective date re-enters service, any annuity previously granted to him and any annuity fixed for his wife shall be cancelled. The policeman shall be credited for annuity purposes with sums sufficient to provide annuities equal to those cancelled for him and his wife, as of their respective ages on the date of re-entrance into service.
Deductions from salary and contributions by the city for all purposes of this Article shall be made, and upon subsequent retirement new annuities based upon the amount then to his credit for annuity purposes and the entire term of his service shall be fixed for the policeman and his wife.
If such policeman's wife, for whom annuity has been fixed prior to his re-entrance into service, has died or her marriage to such policeman has been dissolved or declared invalid before he re-entered service, no part, of any sum or sums to the credit of such policeman for widow's annuity or for widow's prior service annuity at the time annuity for such wife was fixed shall be credited to such policeman at the time of re-entry. No part of any such sum or sums shall be used to provide annuity for any wife of such policeman who is his wife at any time after his re-entry into service unless she was his wife at the time of his withdrawal.
However, the payment of the pension or annuity shall continue if re-entry into service is for the purpose of serving on a part time basis as a street crossing guard.
40 ILCS 5/5-159