115 ILCS 5/4
Employers shall not be required to bargain over matters of inherent managerial policy, which shall include such areas of discretion or policy as the functions of the employer, standards of services, its overall budget, the organizational structure and selection of new employees and direction of employees. Employers, however, shall be required to bargain collectively with regard to policy matters directly affecting wages, hours and terms and conditions of employment as well as the impact thereon upon request by employee representatives, except as provided in Section 10.5. To preserve the rights of employers and exclusive representatives which have established collective bargaining relationships or negotiated collective bargaining agreements prior to the effective date of this Act, employers shall be required to bargain collectively with regard to any matter concerning wages, hours or conditions of employment about which they have bargained for and agreed to in a collective bargaining agreement prior to the effective date of this Act, except as provided in Section 10.5.
115 ILCS 5/4