820 ILCS 180/25: Existing leave usable for addressing domestic violence, sexual violence, gender violence, or any criminal violence.

An employee who is entitled to take paid or unpaid leave (including family, medical, sick, annual, personal, or similar leave) from employment, pursuant to federal, State, or local law, a collective bargaining agreement, or an employment benefits program or plan, may elect to substitute any period of such leave for an equivalent period of leave provided under Section 20. The employer may not require the employee to substitute available paid or unpaid leave for leave provided under Section 20.