Montana law does justify force to defend a home or other property, but only against a person who is entering, attacking, or interfering unlawfully, and only to the extent reasonably necessary. In a partner or family member assault (PFMA) case that first condition is the difficulty when the other person lives there or co-owns the property. This page explains the two statutes and their limits. It is part of our Montana Domestic Violence Guide.
The Two Property-Defense Statutes
| Statute | When force is justified | When force likely to cause death or serious bodily harm is justified |
|---|---|---|
| Occupied structure (MCA § 45-3-103) | To prevent or terminate another person's unlawful entry into or attack upon an occupied structure | Only if an entry is made or attempted and you reasonably believe the force is necessary to prevent an assault on someone inside, or to prevent a forcible felony in the structure |
| Other property (MCA § 45-3-104) | To prevent or terminate a trespass on, or other tortious or criminal interference with, land or personal property lawfully in your possession or that of an immediate family or household member | Only if you reasonably believe the force is necessary to prevent a forcible felony |
Both statutes use the same opening test as ordinary self-defense: force is justified "when and to the extent that the person reasonably believes" it is necessary. Both are affirmative defenses (MCA § 45-3-115), and once the defendant offers evidence of justification the State must prove beyond a reasonable doubt that the actions were not justified (MCA § 46-16-131).
What Counts as an Occupied Structure
An occupied structure is "any building, vehicle, or other place suitable for human occupancy or night lodging of persons or for carrying on business, whether or not a person is actually present." It includes an outbuilding immediately adjacent to or close by that is habitually used for personal use or employment, and each separately secured unit in a building is its own occupied structure (MCA § 45-2-101(47)).
So a house, an apartment, a camper, a vehicle, and a detached shop can all qualify. Land, a yard, and personal items fall under the other-property statute instead.
The Limit That Matters Most: "Unlawful"
MCA § 45-3-103 covers an "unlawful entry into or attack upon" the structure. MCA § 45-3-104 covers "trespass on or other tortious or criminal interference with" property. Neither statute says anything specific about spouses, partners, or roommates, so the ordinary meaning of those words controls.
A person who lives in a home, or is on the lease or the title, or is there with permission, generally is not entering unlawfully. A person who picks up or uses property that both of you own is generally not trespassing on it. In those situations the property-defense statutes generally do not apply, and the case will be decided under the ordinary self-defense rule or on the elements of the charge. How a court would treat a particular living arrangement depends on the facts, and it is a question to take to a lawyer.
The picture is different when the other person truly has no right to be there: a former partner who moved out and forces a door, for example, or a person a court has ordered to stay away. Even then, the next two limits still apply.
How Much Force
Force has to match the need. Under MCA § 45-3-103(2), force likely to cause death or serious bodily harm in defense of an occupied structure is justified only if the entry is made or attempted and the person reasonably believes that force is necessary to prevent an assault on the person or another then in the structure, or reasonably believes it is necessary to prevent a forcible felony in the structure. For other property, such force is justified only to prevent a forcible felony (MCA § 45-3-104). A forcible felony is a felony that involves the use or threat of physical force or violence against any individual (MCA § 45-3-101(2)).
Put plainly, Montana law does not justify seriously hurting a person to protect a phone, a vehicle, or a door.
If You Provoked the Encounter
MCA § 45-3-105 applies to the property statutes just as it does to self-defense. The justification is not available to a person who purposely or knowingly provokes the use of force against himself or herself, unless one of two narrow exceptions is met (reasonable fear of death or serious bodily harm with every reasonable means of escape exhausted, or a clear, good faith withdrawal that the other person ignores).
Common Situations in Domestic Cases
- Blocking a door or taking a phone. Stopping a person from leaving, or taking a phone during an argument, is not defense of property, and it can lead to additional charges. See criminal endangerment and unlawful restraint.
- Shared belongings. A struggle over a jointly owned item is a hard fit for a property-defense claim. Damage to shared property is its own topic: see property damage in a domestic dispute.
- After an order is issued. A no contact order or an order of protection can decide who may be at the residence. If the order restrains you, you may not return, even to a home you own. See where you can live and getting your belongings from home.
- A real break-in by a former partner. This is where MCA § 45-3-103 is most likely to apply. Call 911 as soon as it is safe to do so.
How This Defense Is Raised
Like self-defense, a property-based justification requires written notice to the prosecutor within 30 days after arraignment, or later if the court allows for good cause (MCA § 46-15-323(2)). The evidence that matters is about who had the right to be where: the lease or deed, any court orders, messages about moving out, and what the body camera and 911 recordings show. Our overview of PFMA defenses shows where this fits with the other defenses.
If you are in danger in your home, call 911. The National Domestic Violence Hotline is 1-800-799-7233.
This page explains Montana law in general as of the 2025 Montana Code Annotated. It is not legal advice about your specific case.