40 ILCS 5/14-144: Authorizations.

Members shall, by virtue of the payment of the contributions required to be paid to this system, receive a vested interest in their accumulated contributions in the system, and, in consideration of such vested interest, each member is deemed to have agreed to and authorized the deductions from salary of all contributions payable to this system.

Payment of salary as prescribed by law or as contracted by a department, less the amounts of contributions provided in this Article, shall, together with such special vested rights, be a full and complete discharge of all claims of payments for service rendered by a member to the State during the period covered by any such payment.