No. Montana does not have a statute that requires officers to arrest someone on every domestic call. What it has is a statute that makes arrest the preferred response in four kinds of situations, plus a reporting rule that makes officers explain themselves when they do not arrest. Together those rules lean toward arrest, but the law leaves the officer a decision to make. This page reads the statute closely. It is part of our Montana Domestic Violence Guide.
What the Statute Actually Says
The arrest rule is MCA § 46-6-311. Subsection (1) is the general power: a peace officer "may arrest a person when a warrant has not been issued if the officer has probable cause to believe that the person is committing an offense or that the person has committed an offense and existing circumstances require immediate arrest."
Subsection (2)(a) is the domestic violence provision. It has two sentences. The first says that the summoning of a peace officer to a place of residence by a partner or family member "constitutes an exigent circumstance for making an arrest." The second says: "Arrest is the preferred response in partner or family member assault cases involving injury to the victim, use or threatened use of a weapon, violation of a restraining order, or other imminent danger to the victim."
Preferred Is Not the Same as Mandatory
A mandatory arrest law, as the term is generally used, is one that says an officer "shall" arrest when certain facts are present. Montana's statute uses a different word.
| Point | A mandatory arrest law | Montana (§§ 46-6-311, 46-6-601) |
|---|---|---|
| Wording | An officer "shall" arrest when stated conditions are met. | "Arrest is the preferred response" in four listed situations. |
| Officer discretion | Removed once the conditions are met. | Kept. The general arrest power says an officer "may" arrest. |
| If no arrest is made | Not applicable when the conditions are met. | The officer must file a written report giving the reasons. |
The first column describes the general idea of a mandatory arrest law, not any particular state's statute. The point is the contrast: in Montana the officer still has to decide.
Why the Law Still Leans Toward Arrest
Three features of the law push in the same direction.
- The preference covers common facts. PFMA itself is defined by bodily injury or reasonable apprehension of bodily injury (MCA § 45-5-206(1)). Bodily injury includes physical pain (MCA § 45-2-101). So a scene where an officer finds probable cause for PFMA can also involve "injury to the victim."
- Not arresting takes paperwork. When an officer is called to a reported incident of domestic violence and does not make an arrest, the officer "shall file a written report" with the commanding officer "setting forth the reason or reasons for the decision" (MCA § 46-6-601).
- The call itself supports acting now. The statute treats a partner or family member's call to a residence as an exigent circumstance for making an arrest.
None of this removes the first requirement. Without probable cause that an offense was committed, there is no lawful arrest, preferred or otherwise.
When Both People Used Force
The statute does not tell officers to arrest everyone involved. If it appears the parties were involved in mutual aggression, the officer "shall evaluate the situation to determine who is the predominant aggressor," and if the officer determines that one person is, the officer "may arrest only the predominant aggressor" (MCA § 46-6-311(2)(b)). The six considerations are covered in predominant aggressor factors, and the harder case is covered in when both people are arrested.
If You Are Arrested: How Long in Jail
A judge may post a bail schedule, and an officer may accept bail under it (MCA § 46-9-302(1), (2)). That route is closed here. A person "may not be released on bail without first appearing before the judge" when the offense is any assault on a partner or family member, strangulation of a partner or family member, stalking, violation of an order of protection, or violation of a no contact order (MCA § 46-9-302(1)).
An arrested person must be taken before a judge "without unnecessary delay" (MCA § 46-7-101(1)). The statute does not put a number of hours on that, and timing depends on when the arrest happens and on the court's schedule. See bail in a PFMA case and the initial appearance.
One more exception to know: a person generally may not be arrested at home at night for a misdemeanor committed at some other time and place without a judge's direction on a warrant, but that limit does not apply to an arrest under § 46-6-311 for partner or family member assault (MCA § 46-6-105).
If No One Is Arrested
A decision not to arrest at the scene is not a decision not to charge. The report still exists, the prosecutor can still review it, and a charge can follow by warrant or summons. If you were the subject of a call and no one was arrested, it is reasonable to talk to a lawyer before talking further to police.
What This Means for Your Case
Because the arrest decision is discretionary and made quickly, it can be made on incomplete information. That cuts both ways. The fact of an arrest proves nothing at trial, where the State must prove each element beyond a reasonable doubt. And the details of how the officer reached the decision, including what was seen, who was asked what, and what went into the report, can matter later. Our overview of what happens when police are called covers the rest of the sequence, and our domestic violence defense pagedescribes how A&M Law handles these cases.
This page explains Montana law in general as of the 2025 Montana Code Annotated. It is not legal advice about your specific case.