20 ILCS 3955/30
When appointed by the court pursuant to the "Probate Act of 1975", approved August 7, 1975, as now or hereafter amended, the State Guardian shall serve as guardian, either plenary or limited; temporary guardian; testamentary guardian; or successor guardian; of the person or the estate, or both, of a ward. If nomination is testamentary the State Guardian shall be notified in writing at the time of the death of the testator. The Office of State Guardian may file a petition for its own appointment, or for the appointment of any other person, if the State Guardian determines that the filing of the petition may avoid the need for State guardianship. In addition, the State Guardian may assist the court, as the court may request, in proceedings for the appointment of a guardian and in the supervision of persons and agencies which have been appointed as guardians.
20 ILCS 3955/30