605 ILCS 5/9-103
Whenever a highway has been closed as provided in Section 9-102 or wherever traffic control devices or signs have been erected on any public highway as provided under this Code it is unlawful for any person to remove or knowingly possess any such barrier, traffic control device or sign, or to deface or injure the same, or to walk, ride or drive upon any part of such highway so closed, except such persons as are duly authorized to do so.
Whoever knowingly violates the provisions of this Section shall be guilty of a Class A misdemeanor, punishable by a fine of at least $500, as well as any other penalty which may be imposed. In addition thereto, such person convicted shall be held liable for any and all damages caused to such highway, including, but not limited to, any bridge or culvert work, traffic control device or sign, by reason of such violation.
The highway authorities or their duly authorized agents in direct charge of the work, are authorized to exercise in their respective jurisdictions, all the common law and statutory powers conferred upon sheriffs, and such highway authorities, or their duly authorized agents in direct charge of the work aforesaid, shall arrest without process any person who violates the provisions of this Section, and in so doing they shall be held to be acting for the State.
Any person or persons so arrested shall be delivered by the person making the arrest to some judge, sheriff, or police officer at some station or place within the county in which the offense was committed, for trial, according to law.
605 ILCS 5/9-103