405 ILCS 22/50
The authority or duty to establish or prohibit the establishment of Expanded Mental Health Services Programs in any municipality with more than 1,000,000 inhabitants, including home rule units, and the determination of the terms of such Programs are declared to be exclusive powers and functions of the State which may not be exercised concurrently by any such municipality. No municipality with more than 1,000,000 inhabitants, including home rule units, shall establish or maintain an Expanded Mental Health Services Program other than as provided in this Act, and any such municipality shall affirmatively establish and maintain an Expanded Mental Health Services Program when required to do so pursuant to this Act. This Section is a denial and limitation of home rule powers and functions under subsection (h) of Section 6 of Article VII of the Illinois Constitution.
405 ILCS 22/50