The Texas Penal Code provides that posting “no trespassing” signs that would reasonably come to the attention to the intruders has the effect of providing notice that entry is forbidden. Once notice is provided, entering or remaining on the property without the consent of the owner becomes a violation of Section 30.05 of the Texas Penal Code. A violator of Section 30.05 is charged with criminal trespass, a misdemeanor.
'No Trespassing' Sign
The "no trespassing" sign must be reasonably likely to come to the attention of the intruder to be a valid form of notice. The sign does not have to be professionally made. It must be posted on the property. If it is a building, the sign should be posted at the entrance. A "no trespassing sign" is only effectively providing notice if it stays up, that is why other methods of notice may be more effective.
Other Forms of Notice
A sign is not the only method of providing notice. Oral or written notice is accepted under the law. A fence can be notice. Instead of a fence, you can spray-paint trees with a 1-foot long vertical stripe that is at least 3 feet off the ground so people can see it. Finally, a farm that is growing a crop for human consumption can be notice that entry is forbidden.
Defense to Trespassing
You must own the property or have a greater right of possession to it than the person you are trespassing. For example, if your boyfriend is on the apartment lease, you cannot trespass him. In Vanderburg v. State, the court held a "no trespassing" sign is not effective against a joint owner of the property. You may not successfully keep police off your property just with a "no trespassing" sign. In Rosalez v. State, police officers were permitted to come onto property to conduct a crime investigation without being convicted of criminal trespass.
If you choose to enforce your "no trespassing" sign warning, you will need to call the police to arrest the trespasser. The police will need to document the locations of the signs, preferably with a photograph, to use at trial.