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 Connecticut, property owners can use 'No Trespassing' signs to deter unauthorized entry and limit liability. Under Connecticut law, specifically Connecticut General Statutes Section 53a-107, a person commits criminal trespass when they enter or remain on property without permission and after being told to leave or when they enter property that is reasonably designated as private through fencing or signage. Posting 'No Trespassing' signs clearly informs individuals that they are not permitted to enter the property, which can establish the basis for criminal trespass charges if someone enters without permission. Additionally, Connecticut follows the common law tradition where landowners owe a lower duty of care to trespassers compared to invitees or licensees. This means that if a trespasser is injured on the property, the landowner may have a stronger defense against liability claims, especially if the trespasser was adequately warned by 'No Trespassing' signs. However, this does not absolve property owners of all responsibility; they cannot willfully or wantonly cause injury to trespassers.