20 ILCS 2310/2310-110
To define the boundaries of defense zones within this State for public health purposes, to alter those boundaries from time to time, to establish and maintain health departments in those defense zones, and to prescribe their powers and duties; provided, that no city, village, or incorporated town that has established and is maintaining a board of health or public health board or department pursuant to the provisions of the Illinois Municipal Code, or any portion of that municipality or any territory owned by, leased to, or subject to the jurisdiction of any such municipality, shall be included within any such defense zone except upon approval of the corporate authorities of the municipality or of the mayor or president of the board of trustees of the municipality unless or until that approval is rescinded by action of the city council or board of trustees; provided, that in cities and villages under the commission form of government, that approval must be concurred in by a majority of the council.
20 ILCS 2310/2310-110