Montana generally allows adults to own and carry common knives openly or concealed without a knife permit or general blade-length limit. The state repealed its switchblade prohibition in 2019, and the current statutory definition of “concealed weapon” applies to firearms, not knives. [1] [2]
Montana’s four-inch knife measurement is important in school buildings. It is not a general statewide limit for adult carry elsewhere.
What knives may you own in Montana?
Montana does not impose a general state ban on adult ownership of ordinary folders, fixed blades, switchblades, automatic knives, OTF knives, daggers, or balisongs. Montana Code § 45-8-331, the former switchblade provision, is repealed. [2]
Ownership does not authorize criminal use, threatening conduct, possession in a school building, or violation of private-property rules.
May you openly or discreetly carry a knife?
Montana Code § 45-8-315 now defines “concealed weapon” as a firearm wholly or partially covered by clothing. Knives are no longer included in that definition. Montana therefore does not generally require a concealed-weapons permit merely because a lawful knife is covered by clothing. [1]
Open or concealed carry does not authorize assault, intimidation, disorderly conduct, or use of a knife during another offense. Keep the knife closed or sheathed when not in use.
Are automatic knives and switchblades legal?
Yes. In 2019, Montana repealed § 45-8-331, which had restricted switchblades. Automatic and OTF knives are not prohibited merely because of the opening mechanism. [2]
Federal commerce and shipping rules can still apply, and school-building restrictions are based on blade length and other weapon categories.
What rules apply in school buildings?
Montana Code § 45-8-361 prohibits purposeful and knowing possession, carry, or storage of a weapon in a school building, subject to advance permission and statutory exceptions. For this section, “weapon” includes a knife with a blade four inches or longer, a sword, straight razor, throwing star, nunchaku, metal knuckles, and an article possessed for the purpose of committing a criminal offense. [3]
School policies may prohibit smaller knives and may cover grounds, transportation, and student activities beyond the criminal statute’s “school building” wording. Practical rule: do not bring any knife to school without clear written authorization.
Does Montana preempt local knife ordinances?
Yes. Section 45-8-352 generally prohibits local governments from restricting or prohibiting ownership, use, possession, or sale of a knife not specifically prohibited by state law. A local government may still prohibit knives on property or in a building it owns, leases, or possesses. [4]
The preemption rule does not override state criminal law, tribal law, federal law, school authority, or private-property rules.
What tribal, federal, and private-property rules matter?
Montana includes tribal lands and federal property where separate sovereign rules can apply. Do not assume state law governs every reservation, national park building, federal facility, or military property.
Employers, businesses, venues, and property owners may prohibit knives. Comply with screening, posted rules, and requests to remove the knife or leave.
What vehicle and air-travel rules apply?
Montana does not impose a general requirement that a lawful adult knife be locked in a vehicle trunk. Keep it closed or sheathed and secured against movement. Another jurisdiction’s law applies after crossing a state or tribal boundary.
The Transportation Security Administration prohibits knives in carry-on baggage except for plastic or round-bladed butter knives. Checked-baggage and airline requirements still apply. [5]
What should you verify before carrying?
- Whether the destination is a school building and the blade is four inches or longer.
- Whether a school policy prohibits smaller knives.
- Whether the location is tribal land, federal property, a courthouse, secure facility, employer, venue, or private property with separate rules.
- Whether a local-government-owned property uses the exception in § 45-8-352.
- Whether another state’s law applies to the trip.
Conclusion
Montana generally permits common and automatic knives to be owned and carried openly or concealed. The former switchblade ban is repealed, and state law preempts most local knife restrictions. The clearest knife-specific location rule concerns blades four inches or longer in school buildings, while local-government property, tribal and federal lands, schools, and private property require separate checks.
Last reviewed: August 24, 2026.
This article provides general information, not legal advice. Knife laws and their interpretation can change and may depend on blade measurement, purpose, location, property ownership, tribal or federal jurisdiction, and conduct. Verify current law through official sources or consult a qualified Montana attorney about a specific situation.
Sources & References
- [1] Montana Code Annotated § 45-8-315. Current definition of concealed weapon.
- [2] Montana Code Annotated § 45-8-331. Official page showing the former switchblade provision is repealed.
- [3] Montana Code Annotated § 45-8-361. Weapons in school buildings, four-inch knife definition, permission, and exceptions.
- [4] Montana Code Annotated § 45-8-352. State preemption of local knife regulation and local-government property exception.
- [5] Transportation Security Administration — Knives. Federal carry-on and checked-baggage guidance.
