65 ILCS 97/50
It is declared to be the law of this State, pursuant to paragraph (h) of Section 6 of Article VII of the Illinois Constitution, that the authority or duty to establish or prohibit the establishment of neighborhood security patrol 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, except as otherwise provided in this Section. No municipality with more than 1,000,000 inhabitants, including home rule units, shall establish or maintain a neighborhood security patrol program other than as provided in this Act, and any such municipality shall affirmatively establish and maintain a neighborhood security patrol program when required to do so pursuant to this Act, except that this Section shall not be construed to prohibit the operation of a neighborhood security patrol program created by a municipal ordinance adopted before the effective date of this Act.
65 ILCS 97/50