Are Butterfly Knives Illegal in Colorado?

Colorado Butterfly Knife Laws at a Glance

Butterfly knives — also known as balisongs or fan knives — occupy an interesting gray area in Colorado law. Unlike states such as California or Hawaii that explicitly outlaw them, Colorado has no statewide statute specifically banning butterfly knives. However, this doesn't mean you can freely carry one anywhere in the state.

The legal landscape in Colorado is shaped by a combination of state statutes, municipal ordinances, and law enforcement interpretation. Understanding each layer is essential for anyone who owns, collects, or carries butterfly knives in the Centennial State.

What Colorado Law Actually Says

Colorado Revised Statutes (C.R.S.) § 18-12-101 defines illegal weapons and knife-related offenses. The statute focuses primarily on automatic (switchblade) knives, ballistic knives, and gravity knives — but butterfly knives are not explicitly named in the prohibited list.

The critical nuance is whether a balisong would be classified as a "gravity knife" under Colorado law. A gravity knife is generally defined as one whose blade opens by gravity or centrifugal force. Since balisongs open by centrifugal force through a flipping motion, some law enforcement officers and prosecutors may interpret them as gravity knives — which are illegal in Colorado.

This ambiguity is not trivial. Colorado does not provide a statutory definition of "gravity knife" with the precision that, say, New York law does. This means that whether your butterfly knife is legal can depend on who is interpreting the law, when they're interpreting it, and what context you're in.

Open Carry vs. Concealed Carry

Colorado allows open carry of most knives without a specific blade-length restriction under state law. However, concealed carry of a knife with a blade longer than 3.5 inches can be a criminal offense (C.R.S. § 18-12-105).

• Most butterfly knives have blades in the 3.5–4.5 inch range, making concealed carry potentially illegal.
• Open carry in plain view may be permissible under state law, but local city ordinances can override this.
• Denver, Boulder, and other cities have stricter knife ordinances than Colorado state law.

"Concealed" has a specific legal meaning. A knife in a visible sheath on your belt is generally considered openly carried. A knife in your pocket, however, could be argued as concealed — even if the clip is partially visible.

Denver's Knife Ordinances

Denver Municipal Code § 38-117 restricts carrying knives with blades longer than 3.5 inches in many public areas. Since most balisongs exceed this threshold, carrying a butterfly knife in Denver — even openly — could result in a fine or misdemeanor charge.

Beyond Denver, other Colorado municipalities have their own knife regulations. Colorado Springs, Aurora, and Fort Collins each have ordinances that may differ from state law.

The Gravity Knife Interpretation Problem

The single biggest legal risk for butterfly knife owners in Colorado is the gravity knife interpretation. Because C.R.S. § 18-12-101 prohibits gravity knives, and because balisongs technically deploy via centrifugal force, there is a real possibility that law enforcement could classify your butterfly knife as a prohibited gravity knife.

This interpretation has not been definitively settled by Colorado appellate courts. Some legal scholars argue that a balisong is fundamentally different from a traditional gravity knife because the user's manual manipulation is integral to the opening process. Others argue that any knife that opens via centrifugal force meets the statutory definition.

Practical Takeaways

• Ownership of a butterfly knife in your home is almost certainly legal.
• Carrying it outside — especially concealed — carries genuine legal risk.
• The "gravity knife" interpretation creates significant uncertainty.
• Locality matters enormously — Denver ≠ rural Colorado.
• Always check your city or county ordinances before carrying.
• Even if you are within your legal rights, being stopped by police with a butterfly knife can lead to detention, confiscation, and stressful legal proceedings.

Tips for Butterfly Knife Enthusiasts

If you want to practice with butterfly knives as a hobby — the flipping tricks and dexterity exercises are genuinely enjoyable — consider using a balisong trainer (a dull, blade-free practice version) to stay completely in the clear legally while developing your skills.

There are also communities of Colorado butterfly knife enthusiasts who organize meetups and practice sessions at private venues.