820 ILCS 30/2
No person shall knowingly employ any professional strikebreaker in the place of an employee, whose work has ceased as a direct consequence of a lockout or strike, or knowingly contract with a day and temporary labor service agency to provide a replacement for the employee, during any period when a lockout or strike is in progress. Nor shall any professional strikebreaker take or offer to take the place in employment of employees involved in a lockout or strike.
Nothing in this amendatory Act of the 93rd General Assembly shall be construed to prohibit the continued employment of a day or temporary laborer by an employer if the day or temporary laborer had already been assigned to work for the employer at the time the strike or lockout began.
820 ILCS 30/2