No specific type of knife is illegal to own in Idaho under state law. The only knife that is flatly banned for Idahoans is the ballistic knife, and that prohibition comes from federal law, not the state. Everything else — including switchblades, butterfly knives, dirks, daggers, and bowie knives — is legal to own and legal to carry openly for adults. What Idaho regulates is how long the blade is, whether the knife is concealed, and where you take it.
The One Knife That Is Actually Illegal
Ballistic knives are the exception to Idaho’s otherwise permissive approach. These are knives with a detachable blade propelled by a spring-loaded mechanism. Under 15 U.S.C. 1245, possessing, manufacturing, selling, or importing a ballistic knife is a federal crime punishable by up to ten years in prison.1Office of the Law Revision Counsel. 15 U.S. Code 1245 – Ballistic Knives Because federal law applies in every state, this is the closest thing to a true knife ban affecting Idaho residents.
Why No Other Knife Type Is Banned
Idaho’s knife rules run through Idaho Code 18-3302, which defines a “deadly weapon” to include dirk knives, bowie knives, daggers, and any other weapon designed and manufactured for offensive or defensive purposes. The label matters for concealed carry rules, not for whether you can own the knife.2Idaho State Legislature. Idaho Code Section 18-3302 – Concealed Weapons
Three categories are carved out of the deadly weapon definition entirely:
- Any knife with a blade of six inches or less, even a small dirk or dagger.
- Any knife, cleaver, or similar tool intended for processing, preparing, or eating food.
- Tasers, stun guns, pepper spray, and mace.
For most everyday knives, that six-inch exclusion settles the question: the knife is outside the concealed weapons law and faces no state restriction on how you carry it.2Idaho State Legislature. Idaho Code Section 18-3302 – Concealed Weapons
Knives that do qualify as deadly weapons — a bowie with a long blade, for example — remain legal to own and legal to carry openly. The statute says deadly weapons in plain view are not restricted. Concealed carry of a deadly weapon is also allowed without a license for adults 18 and over who are U.S. citizens or current members of the armed forces and are not otherwise disqualified from a concealed weapons license. Concealed carry by someone who doesn’t meet those conditions is a misdemeanor.2Idaho State Legislature. Idaho Code Section 18-3302 – Concealed Weapons
Switchblades, Butterfly Knives, and Automatics
Idaho does not ban switchblades, automatic knives, butterfly knives (balisongs), or gravity knives. None appear on the list of named deadly weapons, and none are singled out for prohibition anywhere in the state’s criminal code. With a blade of six inches or less, you can carry one concealed with no legal issue. With a longer blade, the knife likely falls under the catch-all for weapons designed for offensive or defensive purposes, so the concealed carry rules above apply.
Federal law adds one wrinkle for buyers: the Switchblade Knife Act prohibits shipping switchblades across state lines through interstate commerce.3Office of the Law Revision Counsel. 15 U.S. Code 1242 – Introduction, Manufacture for Introduction, Transportation or Distribution in Interstate Commerce; Penalty Owning or carrying one inside Idaho is unaffected, but buying from an out-of-state seller can be.
Places You Still Can’t Carry
Even a legal knife becomes a legal problem in the wrong place.
Schools
Possessing a deadly or dangerous weapon on school property, on a school bus, or at any school-sponsored activity is a misdemeanor, and the ban follows students to off-campus school events. The statute carves out a common pocketknife with a short blade. A violation carries up to one year in jail, a fine of up to $1,000, or both.4Idaho State Legislature. Idaho Code 18-3302D – Possessing Weapons or Firearms on School Property
Courthouses, Jails, and Juvenile Detention Facilities
Idaho Code 18-3302C prohibits carrying a concealed deadly weapon in any courthouse, jail, or juvenile detention facility, and it applies even if you have a concealed carry license or qualify for permitless carry. Peace officers acting in their official capacity, on-duty security personnel, and anyone specifically authorized by the entity controlling the building are excepted. A violation is a misdemeanor.5Idaho State Legislature. Idaho Code Section 18-3302C – Prohibited Conduct
Federal Buildings
Federal facilities follow federal law. Under 18 U.S.C. 930, possessing a dangerous weapon in a federal building is a crime, though a pocketknife with a blade under two and a half inches is excluded from the definition of “dangerous weapon” for that purpose.6Office of the Law Revision Counsel. 18 USC 930 – Possession of Firearms and Dangerous Weapons in Federal Facilities Federal court facilities apply stricter rules with fewer exceptions.
Rules Are Tighter for Minors
Anyone under 18 faces extra restrictions. Selling a dirk knife, bowie knife, or dagger to a minor without written consent from a parent or guardian is a misdemeanor, with penalties of up to six months in jail and a fine of up to $1,000.7Idaho State Legislature. Idaho Code 18-3302A – Sale of Weapons to Minors
Idaho Code 18-3302E addresses possession. A person under 18 generally may not possess a dirk, bowie, or dagger without written permission from a parent or guardian, or unless accompanied by a parent or guardian. Children under 12 must be accompanied by an adult, regardless of written permission.
Shipping and Air Travel
Automatic-opening knives and ballistic knives cannot be sent through the U.S. Postal Service. Federal law classifies any knife that opens automatically by hand pressure on a button or by gravity or inertia as nonmailable, with limited exceptions for government procurement and shipments between manufacturers and licensed dealers.8Office of the Law Revision Counsel. 18 U.S. Code 1716 – Injurious Articles as Nonmailable Private carriers like UPS or FedEx set their own policies.
TSA prohibits all knives in carry-on bags. Knives are allowed in checked luggage, and TSA recommends sheathing or securely wrapping any sharp items. The final call at the checkpoint rests with the individual officer, so even rounded or blunt-edged knives can be flagged.9Transportation Security Administration. Knives
Cities and Counties Can’t Add Their Own Bans
Since 2024, Idaho has statewide knife preemption under Idaho Code 18-3327, added by House Bill 620. Cities, counties, and other political subdivisions cannot pass their own ordinances regulating the possession, carrying, sale, or transportation of knives. Any local knife rule not expressly authorized by state statute is void. If a knife is legal under state law, it is legal across Idaho.