620 ILCS 25/23
Any airport zoning regulations adopted under this Act may require that a permit be obtained before any new structure or use may be constructed or established and before any existing use or structure may be substantially changed or substantially altered or repaired. In any event, however, all such regulations shall provide that before any non-conforming structure or tree may be replaced, substantially altered or repaired, rebuilt, allowed to grow higher, or replanted, a permit must be secured from the Department or the administrative agency, as the case may be, authorized to administer and enforce the regulations, authorizing such replacement, change or repair. No permit shall be granted that would allow the establishment or creation of an airport hazard or permit a non-conforming structure or tree or non-conforming use to be made or become higher or become a greater hazard to air navigation than it was when the applicable regulation was adopted or than it is when the application for a permit is made. Whenever the Department or administrative agency, as the case may be, determines that a non-conforming use or non-conforming structure or tree has been abandoned or more than 80 percent torn down, destroyed, deteriorated, or decayed: (a) no permit shall be granted that would allow such structure or tree to exceed the applicable height limit or otherwise deviate from the zoning regulations; and (b) whether application is made for a permit under this section or not, the Department or agency, as the case may be, may by appropriate action compel the owner of the non-conforming structure or tree, at his own expense, to lower, remove, reconstruct, or equip such object as may be necessary to conform to the regulations. If the owner of the non-conforming structure or tree shall neglect or refuse to comply with such order for 10 days after notice thereof, the Department or agency, as the case may be, may proceed to have the object so lowered, removed, reconstructed, or equipped and shall have a lien, upon behalf of the State or the political subdivision, as the case may be, upon the land whereon it is or was located, in the amount of the cost and expense thereof. Such lien may be enforced by the Department, on behalf of the State, or by such political subdivision, as the case may be, by an action for the enforcement thereof, as in the case of other liens. Except as provided herein, applications for permits shall be granted.
620 ILCS 25/23