Short answer: in most of the United States a butterfly knife is treated the same as any other folding knife, and the law has moved steadily in that direction since 2010. A small number of states still single them out, and a few cities have their own rules even where the state does not. This page explains how the rules are structured so you can check your own quickly.
Please check your local law before ordering. This is general information, not legal advice, and knife law changes often.
Federal law barely touches you
The Federal Switchblade Act of 1958 (15 U.S.C. 1241 to 1245) is written around interstate commerce, importation and federal land. It is not a general possession rule, and it does not decide what you may own inside your own state. A balisong has no spring and no button. It opens because the two handles swing on pivots and you move them. That mechanical difference is why most state statutes written about automatic knives do not, on their face, reach a butterfly knife at all.
The practical point: your state statute and your city ordinance decide this, not Washington.
The direction of travel since 2010
This is the part most articles miss. Knife law in America has been getting simpler, not stricter. Knife Rights, the advocacy group that does most of this work, reports 46 bills enacted repealing knife restrictions across 30 states and more than 175 cities and towns since 2010. Texas repealed most of its blade restrictions in 2017. New York repealed its gravity knife rule in 2019. Hawaii, which had one of the strictest positions in the country, repealed its butterfly knife rule in 2024.
If you are reading an article written before about 2022, assume it is out of date.
Hawaii, and why it matters everywhere else
Hawaii is the clearest recent example. In 2023 a Ninth Circuit panel held in Teter v. Lopez that Hawaii's butterfly knife rule did not survive Second Amendment scrutiny after the Supreme Court's decision in Bruen. The following year the legislature settled the matter directly: Governor Green signed HB2342 as Act 021 on 14 May 2024, repealing the restrictions on the manufacture, sale, transfer, possession and transport of butterfly knives, switchblades and gravity knives.
One important detail survived that repeal: Hawaii kept its rule on carrying such knives concealed. In practice that means open carry there rather than concealed. It is a good illustration of the general pattern, which is that possession and carry are two separate questions almost everywhere.
The four questions that decide your answer
Every jurisdiction answers these separately, and this is why a simple yes or no about a state is usually wrong.
1. Can you own one at home? In the overwhelming majority of states, yes, without qualification.
2. Can you carry it openly? Usually yes, sometimes with a blade length limit.
3. Can you carry it concealed? This is where most restrictions actually sit. Concealed carry of a folding knife is treated differently from open carry in a large number of states, and a butterfly knife is a folding knife.
4. Does your city have its own rule? See preemption below.
States that treat butterfly knives as a special category
As of 2026 the list is short. New Mexico is the strictest, treating balisongs within its switchblade statute. California, Connecticut, Iowa, Oregon and the District of Columbia each have restrictions that reach butterfly knives in some form, and Hawaii retains its concealed carry rule after the 2024 repeal.
California is worth spelling out because it is the most misunderstood. A California appellate court held that a butterfly knife falls inside the state's switchblade definition at Penal Code 17235, which is written around blades of two inches or longer that can be released with one hand. Penal Code 21510 then addresses carrying such a knife, possessing it in the front of a vehicle in a public place, and selling, loaning or giving it away. Blade length is the hinge the whole thing turns on, so read the statute rather than a summary of it.
Everywhere not named above, the general folding knife rules for your state apply, and those are usually about blade length and concealment rather than about the mechanism.
Preemption: why the state answer is not always the final answer
Preemption means the state legislature has reserved knife law to itself, so a city cannot write its own stricter rule. Where a state has preemption, checking the state statute is enough. Where it does not, a city ordinance can be stricter than the state and you have to check both.
States that have adopted knife law preemption include Alaska, Arizona, Arkansas, Georgia, Idaho, Indiana, Kansas, Louisiana, Montana, New Hampshire, Ohio, Oklahoma, South Carolina, Tennessee, Texas, Utah, West Virginia, Wisconsin and Wyoming.
States without it include California, Colorado, Connecticut, Delaware, Florida, Hawaii, Illinois, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, Nevada, New Jersey, New York, North Carolina, North Dakota, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia and Washington. In those, look up the city as well. New York City, Denver, Chicago, Philadelphia, Boston and New Orleans are the ones that catch people out most often.
Places the rules change regardless of your state
Some locations run on their own rules and no state statute helps you. Airports and aircraft, which means a knife travels in checked baggage or not at all. Schools and college campuses. Courthouses and government buildings. Federal buildings and most federal facilities. National parks vary by park. Crossing an international border resets everything to the rules of the country you are entering.
Age
Several states set a minimum age to buy or possess a knife, commonly 18, and some apply it only to certain knife types. Where there is no state age rule, individual retailers and marketplaces usually set their own. If you are buying for someone under 18, check your state first.
How to check your own state in five minutes
Search for your state name together with the phrase knife law preemption, and separately for your state's criminal code section on dangerous or deadly weapons. Read the definitions section before the offence section, because the definition is what decides whether a butterfly knife is inside the statute at all. Then check whether the rule is about possession, open carry, concealed carry or sale, since those are four different answers. If your state has no preemption, check your city code as well.
Two organisations track this properly and update it: the American Knife and Tool Institute, and Knife Rights. Both publish state summaries with citations. Use those as your starting point and the statute itself as your authority.
Questions people ask
Is a butterfly knife the same thing as a switchblade?
Mechanically, no. A switchblade has a spring and a release. A balisong has two free handles and pivots, and nothing happens unless you move them. Legally, a few states have chosen to fold balisongs into their switchblade definitions anyway, which is why the mechanical answer and the legal answer can differ in the same sentence.
Are trainers treated differently?
A trainer has an unsharpened blade. Some statutes are written around a cutting edge and some are written around the mechanism, so a trainer is not automatically exempt everywhere. Check the definition in your own statute.
Does blade length matter?
Very often it is the only thing that matters. California's threshold sits at two inches. Many states set carry limits somewhere between three and four inches. Measure your blade before assuming.
What about carrying one at work?
An employer can set a stricter rule than the law on its own premises, and that rule is a condition of employment rather than a criminal matter. The same goes for most private property.
Where do I find the actual text?
Every state publishes its criminal code online for free. Search the state name plus the code section rather than relying on a summary. Summaries, including this one, go out of date.
The short version
Most of the country treats a butterfly knife as an ordinary folding knife. The restrictions that remain are concentrated in a handful of states and a handful of cities, and they usually turn on blade length and on whether the knife is concealed rather than on the mechanism itself. The law has been loosening, not tightening, for fifteen years.
Please check your local law before ordering.
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