No trespassing signs can be useful to property owners—especially on large tracts of land or land that is not developed—to put persons entering the property on notice that the property is private property and if they do not have permission to enter, they may be committing civil and criminal offenses related to trespassing. In some states notice is required for a trespasser to have civil or criminal liability for entering the property without permission.

No trespassing signs may also protect a landowner against liability to a trespasser, as a lower duty of care is owed to trespassers in some states, and putting a person entering the property on notice that they are trespassing may strengthen the property owner’s defense against any liability claims if the trespasser is injured on the property.

In Rhode Island, property owners can use 'no trespassing' signs to deter unauthorized entry and limit liability. Under Rhode Island General Laws § 11-44-26, it is a criminal offense to willfully trespass upon the land of another after having been forbidden to do so by the owner or occupant of the land, or by a sign posted on the property. The presence of 'no trespassing' signs serves as a clear notice that entry is not permitted, which is necessary for establishing the offense of trespassing. Additionally, Rhode Island follows the common law tradition where a landowner owes a lower duty of care to trespassers than to invitees or licensees. By posting 'no trespassing' signs, a landowner may strengthen their defense against liability claims should a trespasser be injured on the property, as the signs indicate that the trespasser did not have permission to enter and was therefore on the property unlawfully.