Illinois State Trespassing Laws

Understanding your home state’s trespassing laws is essential if you want to keep your property safe from people that shouldn’t be there while also keeping yourself safe from undue liability.

flag of Illinois

It is easy to overreact when someone is trespassing, and if you use force when you really shouldn’t, it might be you that winds up on the hot seat.

Illinois is a state, as you might expect, with substantial laws on the books covering every aspect of trespassing.

Very lengthy, and not too easy to decipher for those not already fluent in the law, today we are bringing you a guide that will share with you the most important concepts concerning trespassing law in Illinois.

Illinois Trespassing Law Overview

  • Trespassing in Illinois is a misdemeanor, with the exception of repeated violations of a criminal trespass on state supported land, place of amusement, airports or nuclear facilities.
  • Illinois law allows purple paint markings to be used in place of no-trespassing signage for posting real property.
  • People may trespass on abandoned, unoccupied property for the purposes of beautification.

What Constitutes Trespassing in Illinois?

Illinois, unlike most other states, does not have a separate set of definitions that cover the various chapters on trespassing in the state statutes, and instead scatters the definitions around throughout where they are needed.

Accordingly, there is not one clear-cut definition of criminal trespass that you can rely on as it is contextual throughout the statutes

Generally, criminal trespass is knowingly and unlawfully entering or remaining within a building, in or upon land, or in or upon a vehicle of another person without permission or leave to do so, or, having had permission, refusing to leave after the owner or owners agent revokes that permission.

In short, if you don’t have permission under the law you shouldn’t be on someone else’s property, and if you did have permission but that permission was revoked you have to leave, otherwise you are trespassing.

In the case of public places in public buildings, you may only be there during times of occupancy open to the public and if you are told to leave by the owner, manager, owner’s agent, or law enforcement you must depart. Refusing to do so is, you guessed it, criminal trespass.

Sec. 21-3. Criminal trespass to real property

(a) A person commits criminal trespass to real property when he or she:
(1) knowingly and without lawful authority enters or remains within or on a building;
(2) enters upon the land of another, after receiving, prior to the entry, notice from the owner or occupant that the entry is forbidden;
(3) remains upon the land of another, after receiving notice from the owner or occupant to depart;
(3.5) presents false documents or falsely represents his or her identity orally to the owner or occupant of a building or land in order to obtain permission from the owner or occupant to enter or remain in the building or on the land;

Does Illinois Require “No Trespassing” Signs?

Yes, in most cases. For the law to back you up in instances of trespassing, it is generally required that your property be posted at all entrances to, or around the perimeter of, the parcel.

And, in keeping with Illinois tradition of bureaucratic interference your no-trespassing signs must meet a very specific set of standards to have the force of law behind them.

You can look up the specific requirements for signage in Illinois State statutes. Remember, you can’t use just any no-trespassing sign!

Is Fencing Required to Protect Property?

No, fencing is not required to protect property, including undeveloped property, so long as no-trespassing signs or other marks are posted.

See the next section, and remember that if you’re going to post signage or use paint markings they must meet all the requirements of the state statutes to the letter for them to have the force of law behind them!

What Other Marks Indicate “No Trespassing”?

Illinois is one of several states that uses so-called “purple paint” laws when it comes to posting property against trespassing.

The short version is that, using a series of vertical markings made from purple paint at about eye level, these will serve as legal notice against trespassing.

You can read the specifics for these paint markings in section 21-3 below:

Sec. 21-3. Criminal trespass to real property


(b-5) Subject to the provisions of subsection (b-10), as an alternative to the posting of real property as set forth in subsection (b), the owner or lessee of any real property may post the property by placing identifying purple marks on trees or posts around the area to be posted. Each purple mark shall be:
(1) A vertical line of at least 8 inches in length
and the bottom of the mark shall be no less than 3 feet nor more than 5 feet high. Such marks shall be placed no more than 100 feet apart and shall be readily visible to any person approaching the property; or
 (2) A post capped or otherwise marked on at least its top 2 inches. The bottom of the cap or mark shall be not less than 3 feet but not more than 5 feet 6 inches high. Posts so marked shall be placed not more than 36 feet apart and shall be readily visible to any person approaching the property. Prior to applying a cap or mark which is visible from both sides of a fence shared by different property owners or lessees, all such owners or lessees shall concur in the decision to post their own property.

Can Solicitors Ignore “No Trespassing” Signs?

No. A solicitor who is considering approaching your home or crossing other property with the sole intention of selling you something cannot ignore no-trespassing signage or markings so long as they meet the state’s requirements for posting against trespassing.

Do keep in mind, though, that state employees, agents, and law enforcement may generally ignore no-trespassing signs so long as they are lawfully executing their appointed duties.

They don’t really fit into the category of “solicitor”.

Can Trespassing Result in Arrest in Illinois?

Yes, it can; though most types of criminal trespass in Illinois are only misdemeanors in nature, they can still result in arrest.

You should never trespass yourself with the expectation you’ll be let off of the warning or a fine.

Also, repeatedly trespassing upon State supported property, trespassing in the secure area of an airport, and a nuclear plant or a place of amusement is a felony and will definitely result in arrest.

Can You Take Someone to Court for Trespassing?

Yes, you can. You can definitely take someone to court if there is an obvious malicious intent, someone already has a criminal record, or a history of trespassing.

Is also easy to take someone to court if they have damaged property while trespassing or in order to trespass.

Special Instances of Trespassing in Illinois

Quite a few, as alluded to above. Most notably Illinois reserves the most serious charges for trespassing in various sensitive installations or in any state-supported property.

But, most interestingly, people who trespass are exempt from prosecution under the law if they are trespassing only with the intention of “beautifying” an abandoned and unoccupied residential or industrial property.

What does beautifying mean in this case? It could be something like picking up trash, tidying up and generally making the place look nice.

Also keep in mind that for the purposes of this exception a property must be abandoned according to Illinois definition and also unoccupied, and that means even no illegal occupants can be in the property.

This could, for instance, allow good neighbors to clean up an abandoned home on their block in an effort to prevent it from attracting vandals, squatters or otherwise dragging down the property values.

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