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 Massachusetts, property owners can use 'No Trespassing' signs to deter unauthorized entry and limit liability. Under Massachusetts General Laws Chapter 266, Section 120, property owners are allowed to post these signs to provide notice that entry is forbidden. If a person enters the property without permission after such notice has been clearly given, they may be subject to criminal penalties for trespassing. The presence of 'No Trespassing' signs can also impact the duty of care a property owner owes to individuals on their property. Generally, a lower duty of care is owed to trespassers compared to invitees or licensees. This means that if a trespasser is injured on the property, the owner may have a stronger defense against liability claims, as the trespasser was warned against entering the property. However, this does not absolve property owners of all responsibility; they cannot willfully or wantonly cause harm to trespassers.