430 ILCS 115/6: Alteration of mobile structures or modular dwelling units to which seals have been affixed.

(a) A unit of local government may regulate the location of the modular dwellings and mobile structures and their foundation, and the installation of the on-site utilities.

(b) It is unlawful for any person to make any alteration of any mobile structure or modular dwelling unit to which a seal has been affixed if such alteration causes the mobile structure or modular dwelling unit to be in violation of the applicable code.