Black’s Law Dictionary defines trespassing as, “An unlawful act committed against the person or property of another; especially, wrongful entry on another's real property.” In addition to this definition, the dictionary defined trespass in more specific subsections due to the broadness of the term. These classifications are:
- Continuing Trespass: A trespass in the nature of a permanent invasion on another's rights, such as a sign that overhangs another's property.
- Criminal Trespass:1) A trespass on property that is clearly marked against trespass by signs or fences. 2) A trespass in which the trespasser remains on the property after being ordered off by a person authorized to do so.
- Innocent Trespass: A trespass committed either unintentionally or in good faith.
- Joint Trespass: A trespass that two or more persons have united in committing, or that some have actually committed while others commanded, encouraged, or directed it.
Nolo’s Plain-English Law Dictionary states that trespass can be presented in court as either a tort or a crime. The dictionary states that trespass is considered a crime if it is done willfully, while it is a tort if the defendant commits a civil wrong which the plaintiff could sue over. 
Model Penal Code
The Model Penal Code (MPC) § 221.2 separates criminal trespass into two categories and outlines ramifications of the crime:
- Buildings and Occupied Structures: A person commits an offense if, knowing that he is not licensed or privileged to do so, he enters or surreptitiously remains in any building or occupied structure, or separately secured or occupied portion thereof. An offense under this Subsection is a misdemeanor if it is committed in a dwelling at night. Otherwise it is a petty misdemeanor.
- Defiant Trespasser: A person commits an offense if, knowing that he is not licensed or privileged to do so, he enters or remains in any place as to which notice against trespass is given by:
- actual communication to the actor; or
- posting in a manner prescribed by law or reason- ably likely to come to the attention of intruders; or
- fencing or other enclosure manifestly designed to exclude intruders.
An offense under this subsection constitutes a petty misdemeanor if the offender defies an order to leave personally communicated to him by the owner of the premises or other authorized person. Otherwise it is a violation.
Variation by Jurisdiction
Title 14, Section 602 of the California Penal Code defines trespassing as, “entering someone else's property with the intent to damage that property, entering someone else's property with the intent to interfere with or obstruct the business activities conducted thereon, entering and "occupying" another's property without permission, and refusing to leave private property after you've been asked to do so.” On top of this the California Penal Code adds two elements that must be satisfied to establish trespassing, these elements are, “the fact that you willfully willfully enter someone else's property,” and, “with the specific intent to interfere with that person's property rights.” Trespassing violations in California are most frequently prosecuted as misdemeanors and convictions can result in six months in a county jail and a maximum $1,000 fine. However certain violations will only constitute an infraction on ones first offense, an example of this is ignoring a “no trespassing” sign one time without causing any damage to the property.
Title 46, Chapter 810.09 of the Florida Statutes, states that one commits the offense of trespass, on property other than a structure or conveyance, when, “A person who, without being authorized, licensed, or invited, willfully enters upon or remains in any property where notice against entering or remaining is given, either by actual communication to the offender or by posting, fencing, or cultivation as described in s. 810.011.” The perpetrator can be charged with a first-degree misdemeanor if they ignore an order to leave or if they willfully open any door, gate, or fence that exposes the property. Under section 775.082, this offense is punishable by a non state-prison sanction. However, if the offender is armed with a dangerous weapon during his criminal act of trespass, then they are guilty of a third degree felony. Section 775.083 states that this act is punishable by a 5,000 dollar five, a maximum prison sentence of 5 years, or both.
If any person without authority of law goes upon or remains upon the lands, buildings or premises of another, or any portion or area thereof, after having been forbidden to do so, either orally or in writing, by the owner, lessee, custodian, or the agent of any such person, or other person lawfully in charge thereof, or after having been forbidden to do so by a sign or signs posted by or at the direction of such persons or the agent of any such person or by the holder of any easement or other right-of-way authorized by the instrument creating such interest to post such signs on such lands, structures, premises or portion or area thereof at a place or places where it or they may be reasonably seen, or if any person, whether he is the owner, tenant or otherwise entitled to the use of such land, building or premises, goes upon, or remains upon such land, building or premises after having been prohibited from doing so by a court of competent jurisdiction by an order issued pursuant to §§ 16.1-253, 16.1-253.1, 16.1-253.4, 16.1-278.2 through 16.1-278.6, 16.1-278.8, 16.1-278.14, 16.1-278.15, 16.1-279.1, 19.2-152.8, 19.2-152.9 or § 19.2-152.10 or an ex parte order issued pursuant to § 20-103, and after having been served with such order, he shall be guilty of a Class 1 misdemeanor.
Common Defenses to Civil Trespass
There are four main defenses for trespassing: easement, estoppel, necessity and consent. Easement is the legal right to use the property of another when it is not in your possession. The court broadened this term in a New York appellate court decision and declared that an easement granted in general terms must be construed to include any reasonable use which is lawful.Estoppel is when a person who has a duty to speak or act, intentionally or negligently through their action or inaction, made another believe in the existence of a fact that did not exist, and another acted by relying on that act or omission. A defendant can invoke necessity if in an emergency they trespass in order to protect the interests of others or themselves. While the defendant won’t be liable for trespassing, they can still be held accountable for any harm done to the property as caused by the trespass. Trespassing is allowed if the entry to the property is with the consent or license of the person who has a legal ownership of the property or land. This defense has two elements that must be proven on the side of the plaintiff though: 1) there was a voluntary acceptance of an intentionally tortuous act, 2) with full knowledge or understanding of the consequence. 
Illustrations of Civil Defense Cases
- Easement would be the county sheriff entering the property of another to deliver a summons.
- An example of estoppel would be if Person A asked Person B if it was okay to enter his land and Person B said nothing, thus allowing Person A onto his land by his inaction.
- Necessity would be entering a nearby house to take cover from a drive by shooting. However if you break a door getting into the house one would be liable for damages to the door, but not for trespassing.
- An example of consent would be asking for permission to enter the premises of a building and the legal owner agreeing to let you in.
Common Defenses to Criminal Trespass
Criminal trespassing is a misdemeanor offense throughout the United States. Unlike with civil trespass, a criminal defendant cannot be convicted of trespass without proof beyond a reasonable doubt that the defendant not only entered upon the property in question, but did so with knowledge that he was forbidden to do so. There are several common fact patterns in a trespassing case. First, a large category of cases involve a defendant entering upon property that is marked with signage forbidding entry onto the property between certain hours. In such cases, it is a defense that the Government cannot prove that the defendant saw the sign. As a practical matter, though, many courts will presume that a defendant observed well-placed, easily-observable and comprehensible signs. Second, a large category of cases involve a defendant entering upon property from which he has been banned by someone with authority to do so. In such cases, the Government must prove that the defendant received actual notice of the ban. This fact pattern often arises in the United States in public housing projects, where the police or property managers ban persons who they believe have previously caused trouble on the property. Once the ban has been affected, police may arrest and search such persons anytime they enter the property. In the United States, police use trespassing charges/property bans as a law enforcement tool because the bans create an automatic right to arrest and search persons they suspect for drug or other illegal activity. Third, some trespass charges involve property whose very nature renders it obvious that entry thereupon violates the law. For example, a defendant who opened a private door or gate, or climbed a fence, to enter upon property without permission could be convicted of trespassing even in the absence of signage or a ban from the property.
In the UK a police officer has the power to take a person off another’s land or property if: they are present there and seemingly residing for any period of time, reasonable steps have been taken by or on behalf of the legal owner to ask them to leave, and if those persons have caused damage to the land or property. A person guilty of this offense is liable on summary conviction to imprisonment for a term not exceeding three months or a fine not exceeding level 4 on the standard scale, or both.
The Trespass Act 6 of 1959 states that any person who, without the permission of the lawful occupier, owner, or person in charge of any land, building, or part of a building, enters into any of the previously stated premises shall be guilty of trespass unless he has lawful reason to enter the property. This offense is punishable by a fine not exceeding 2000 rand, a maximum prison sentence of 2 years, or both.
- Black’s Law Dictionary, 9th edition (2009)
- Nolo’s Plain-English Law Dictionary, 1st edition (2009)
- Model Penal Code, § 221.2
- California Penal Code, Title 14 § 602
- Florida Statute, Title 46, Chapter 810.09
- Florida Statute, Title 46, Chapter 775.082
- Florida Statute, Title 46, Chapter 775.083
- Code of Virginia, Chapter 5, § 18.2-119
- Phillips v. Jacobsen, 117 A.D.2d 785 (N.Y. App. Div. 2d Dep’t 1986)
- Merrill Stevens Dry Dock Co. v. G & J Invs. Corp., 506 So. 2d 30 (Fla. Dist. Ct. App. 3d Dist.)
- Okrent, Cathy J..Torts and Personal Injury Law. 4th ed. Clifton Park, NY: Delmar Learning, 2009. Print.
- United Kingdom Criminal Justice And Public Order Act 1994, Part V, Section 61
- Constitution of the Republic of South Africa, Trespass Act 6 of 1959