Why Are Butterfly Knives Illegal? The History Behind the Bans

Written by Nathaniel, in the workshop. Last checked 30 August 2026.

Butterfly knives are restricted in some places because of a chain of accidents rather than a considered decision about balisongs. A 1950s American panic about switchblades produced the 1958 Federal Switchblade Act, whose definition caught knives that open “by operation of inertia, gravity, or both.” A balisong has no spring and no button, but it opens by wrist motion, so courts and legislatures folded it into laws written for a different knife entirely.

That is the short version. The long version is more interesting, because the balisong was never the knife anyone was actually frightened of, and because the last fifteen years have quietly undone a lot of what the previous fifty built. Here is the whole sequence, with the statutes and cases named where we could verify them and flagged plainly where we could not.

The knife the law was not written about

A balisong is a manually operated folding knife. Two handles pivot on two pins around a tang; you move them with your hand. There is no spring, no torsion bar, no button, no lever, no stored energy of any kind. Left alone on a table it will sit there forever. Compared to almost any modern folder with a detent and a thumb stud, it is a mechanically primitive object.

This matters because every American law that catches balisongs was drafted to describe something else: a knife that deploys itself. The balisong got swept up in the wording, not the intent. That is the single most useful thing to understand about butterfly knife law.

How the balisong reached the United States

The balisong is a Filipino knife from Batangas province, where the workshops have been making them for well over a century. The fuller account is in our history of the balisong and our page on the original Batangas balisong.

The usual story is that American servicemen brought balisongs home from the Philippines after the Second World War, and again during the Vietnam era, and that this is how the knife entered American pockets. We want to be honest here: that account is repeated in almost every article on the subject, including by people we respect, but we could not find a primary source for it this session. No import records, no contemporaneous news reports, no military documentation. Treat it as plausible folklore rather than established fact.

What is not in dispute is that by the 1980s the balisong had an American following and a reputation. The reputation is what the law responded to.

The 1958 Federal Switchblade Act: what it actually says

The Federal Switchblade Act was enacted as Public Law 85-623 on 12 August 1958 and is codified at 15 U.S.C. sections 1241 to 1245. Section 1241 defines the term:

“any knife having a blade which opens automatically (1) by hand pressure applied to a button or other device in the handle of the knife, or (2) by operation of inertia, gravity, or both.”

Two things get misreported constantly. First, it is a commerce statute: it restricts introducing switchblades into interstate commerce, importing them, and manufacturing or transporting them for interstate commerce. It does not make owning one at home a federal crime. Second, the inertia-and-gravity clause was aimed at gravity knives, a category of European military folders. It was not written with balisongs in mind.

The Act has been amended since. In 2009 Congress added an exemption at 15 U.S.C. 1244(5) covering knives with “a spring, detent, or other mechanism designed to create a bias toward closure of the blade” that requires manual exertion to overcome. That is the clause that protects assisted-opening knives and one-hand openers from being reclassified as switchblades. Section 1244 also carries exemptions for common carriers, Armed Forces contracts and personnel, and for one-armed persons carrying blades of three inches or less.

The panic that produced the law

The 1958 Act was not a response to data. The commonly cited trigger is a November 1950 article in Woman’s Home Companion by Jack Harrison Pollack, titled “The Toy That Kills,” which called switchblades a cause of juvenile delinquency without offering figures. Newspapers ran with it, and between roughly 1954 and 1960 a run of American films put a switchblade in the hand of a delinquent. The association set like concrete.

By the time Congress held hearings, the evidence was thin enough to be embarrassing. Kansas City, Missouri, a city of over 400,000 people, reported around three dozen switchblade incidents in 1956. Both the Department of Justice and the Department of Commerce opposed federal legislation. Representative Sidney R. Yates of Illinois nonetheless described the knives in terms of “vicious fantasies” and “sadistic atrocities.” The bill passed anyway. New York had already banned automatics in 1954.

None of this involved balisongs. In 1958 the balisong was, as far as the American legislative record shows, invisible.

How a knife with no spring got caught in a spring-knife law

The crossover happened at state level, and the cleanest documented example is Californian. In People ex rel. Mautner v. Quattrone (1989) 211 Cal.App.3d 1389, the California Court of Appeal held that butterfly knives fall inside the state’s switchblade prohibition, then at Penal Code section 653k. The court reasoned that “automatically” covered “the sudden and immediate opening or exposing of the knife blade,” and that because a butterfly knife “can be opened rapidly with one hand and is ready for use,” the multiple wrist movements required did not take it outside the statute.

Read that holding twice. The court did not find that a balisong has a spring. It found that opening it quickly was enough. Once a definition turns on speed of use rather than stored energy, a manual knife can be a switchblade. California’s current definition sits at Penal Code section 17235 and still turns on phrases including “flip of the wrist.”

Hawaii took the more direct route and legislated about butterfly knives by name. HRS section 134-53, enacted by 1999 Haw. Sess. Laws c 285, made it a misdemeanour to manufacture, sell, transfer, possess or transport a butterfly knife, described in the statute as “a knife having a blade encased in a split handle that manually unfolds with hand or wrist action with the assistance of inertia, gravity or both.” Note the word “manually” sitting right there in a statute banning the knife for opening automatically.

Timeline

Why the reputation stuck

Laws are easier to pass than to repeal, but reputation is stickier than either. Four things kept the balisong disreputable long after the panic that created the rules had faded.

• It looks like a trick. A knife you can only open impressively is a knife that appears designed to be shown off. Flipping reads as performance, and performance with an edge reads as threat to people who do not know what they are watching.
• It is loud. A balisong opening makes a distinctive metallic clatter. Memorable is not the same as dangerous, but people confuse the two.
• Media repetition. Once a prop enters film and television shorthand as the villain’s knife, every subsequent production reinforces it. The balisong inherited the switchblade’s screen role in the 1980s and never quite gave it back.
• Legislative copy-paste. State weapons statutes are frequently drafted by borrowing language from other states. A definition written in 1958 for a German gravity knife has been copied forward for close to seventy years, picking up balisongs on the way, mostly without anyone re-examining whether it should.

What almost never features in the record is evidence. We looked for crime statistics specifically attributing offences to butterfly knives, in support of any of the bans described above, and did not find any. If such a dataset exists we would genuinely like to see it.

The turn: repeals, preemption and the Second Amendment

Since roughly 2010 the direction of travel has reversed, on three separate tracks.

Legislative repeal. A long run of states have removed automatic-knife bans, among them Missouri and Washington (2012), Alaska, Kansas and Texas (2013), Nevada and Oklahoma (2015), Wisconsin (2016), Colorado, Montana and Illinois (2017), and more recently Vermont and Delaware (2025). Those are automatic-knife reforms rather than balisong-specific ones, but they matter because the two categories are so often defined together.

Preemption. Separately, a number of states have passed knife law preemption, which stops cities and counties writing their own conflicting rules. Arizona went first in 2010, followed over the next fifteen years by states including Utah, Georgia, Kansas, Tennessee, Oklahoma, Texas, Wisconsin, Ohio, Idaho and Arkansas. For an owner, preemption is often more useful than repeal, because the thing that actually catches people out is a municipal ordinance nobody has heard of.

Constitutional litigation. After New York State Rifle & Pistol Association v. Bruen changed the analytical framework for arms regulation, knife cases followed. In Teter v. Lopez, a Ninth Circuit panel held on 7 August 2023 that Hawaii’s flat butterfly knife ban violated the Second Amendment. Hawaii then amended the statute: HB 2342 was signed on 13 May 2024 (2024 Haw. Sess. Laws 21), ending the possession prohibition and leaving a concealed carry restriction the plaintiffs had not challenged. On 22 January 2025 the en banc Ninth Circuit vacated the earlier judgment as moot. The ban is gone; the precedent that killed it is gone too.

In Commonwealth v. Canjura, SJC-13432, decided 27 August 2024, the Massachusetts Supreme Judicial Court applied the same framework to G.L. c. 269, section 10(b) and held that the prohibition on carrying switchblades violated the Second Amendment. The knife in that case was a switchblade, not a balisong, so it does not decide butterfly knife questions directly. It does show a state supreme court asking a government to justify a blade ban historically, and the government failing.

What we could not verify

House rule here: if we did not check it, we say so.

• The claim that American servicemen introduced the balisong to the United States after the Second World War. Widely repeated, no primary source found.
• Any published U.S. Customs and Border Protection ruling squarely deciding whether a balisong is a switchblade under the Federal Switchblade Act. We looked and did not find one.
• Precise enactment years for individual state preemption and repeal laws. Our list above comes from a knife-rights advocacy compilation, not from reading each session law. The pattern is real; treat individual years as approximate.
• The status of the Freedom of Commerce Act, a bill to repeal the Federal Switchblade Act’s interstate commerce restriction. It has been introduced in multiple Congresses. We could not verify that any version has become law, and we assume none has.
• Any crime dataset specifically supporting a butterfly knife ban. Not found.

Where that leaves you

Legality is local, it changes, and it is the one part of this subject where being roughly right is not good enough. We keep a current breakdown in our butterfly knife laws by state guide, and that is the page to read before you order. Butterfly knife laws vary by state, county and city, so check your local law before buying or carrying one.

If your jurisdiction is restrictive, a trainer is the sensible answer, and it is how most people should start anyway.

More reading: the mechanical distinctions behind all of this are covered in our balisong vs switchblade vs automatic guide, the knife itself in what is a balisong knife, the craft tradition in the history of the balisong, buying advice in where to buy butterfly knives, and the current legal picture in balisong laws by state.

Frequently Asked Questions

Are butterfly knives illegal in the United States?

There is no blanket federal ban on owning one. The Federal Switchblade Act regulates interstate commerce, import and manufacture for interstate commerce rather than private possession. Legality is decided at state and often municipal level, and it varies widely. Check our laws by state guide and your local ordinances before you buy or carry.

Why is a balisong treated as a switchblade when it has no spring?

Because several statutory definitions turn on how fast a knife can be brought into use, not on whether it deploys under stored energy. The 1958 federal definition includes knives opening “by operation of inertia, gravity, or both,” and in 1989 a California appellate court held in Quattrone that opening quickly with one hand was enough to qualify.

What did the Federal Switchblade Act of 1958 actually ban?

Public Law 85-623 restricted introducing switchblade knives into interstate commerce, importing them, and manufacturing or transporting them for interstate commerce. It did not create a federal offence of simple possession. Congress added exemptions over time, including a 2009 provision protecting assisted-opening knives with a bias toward closure.

Did soldiers really bring balisongs back from the Philippines?

It is the standard story and it may well be true, but we could not find a primary source confirming it. No import records, no contemporaneous reporting, no military documentation surfaced in our research. We flag it as folklore rather than fact. The knife’s Batangas origins, by contrast, are well documented.

What was Commonwealth v. Canjura?

A 2024 Massachusetts Supreme Judicial Court decision, docket SJC-13432, decided 27 August 2024. Applying the Bruen framework, the court held that the state’s prohibition on carrying switchblades under G.L. c. 269, section 10(b) violated the Second Amendment. The knife was a switchblade, not a butterfly knife, so it does not decide balisong cases directly.

Is Hawaii’s butterfly knife ban still in force?

No. HRS 134-53, enacted in 1999, banned possession outright. After a Ninth Circuit panel held that unconstitutional in 2023, Hawaii amended the statute through HB 2342, signed 13 May 2024, ending the flat possession ban and leaving a concealed carry restriction. The en banc court then vacated the 2023 ruling as moot in January 2025.

Are knife laws getting stricter or looser?

Looser, over the last fifteen years or so, on three tracks: legislative repeal of automatic-knife bans in a long list of states, preemption statutes stopping cities writing conflicting rules, and constitutional litigation after Bruen. That trend is real but uneven, and it does not mean any particular knife is legal where you live.

Does a trainer avoid the legal problem entirely?

Not automatically. Some statutes are written around the mechanism rather than the edge, which can capture unsharpened trainers too. In practice a trainer is far less likely to cause trouble than a live blade, and it is the right learning tool anyway, but it is not a guaranteed workaround. Verify your local wording.

Why do so many articles about this contradict each other?

Because knife law is fifty-plus separate systems, it changes frequently, and most articles copy each other rather than reading statutes. Court decisions get reported as national rules when they bind one state. Repeals get missed for years. Read the date on anything you find, and prefer the statute text to a summary of it.

Where can I read the current state-by-state position?

Our laws by state guide is the page we maintain for that, and it is deliberately kept separate from this history article so it can be updated as things change. This page explains why the rules exist. That one tells you what they currently say. Both should be read before ordering.

Related guides

• Travelling With a Balisong: Flights, Borders and Shipping. What the same history means in practice when you actually need to move a balisong from one place to another.