Knife law in the US is a patchwork of federal, state, and local rules that frequently overlap and sometimes conflict. Rather than attempting to list specific statutes (which change and vary too much by location to summarize reliably), this guide covers the general categories of restriction that matter and where to look for current, location-specific information.
Federal Law Basics
Federal law primarily addresses interstate transport and import of certain knife types rather than general possession. The federal Switchblade Act restricts the interstate shipment and import of true automatic (switchblade) knives, though it includes exceptions, including for certain government and military uses. Most folding knives covered in TrailCraft's reviews — including assisted-opening designs like the Kershaw Leek — are legally distinct from switchblades under federal law because they require manual force to begin opening, but local and state classifications can vary, which is why verifying local law remains important.
State and Local Variation
Common categories that states and municipalities regulate include maximum blade length (commonly somewhere in a 2.5 to 4 inch range, though specific limits vary considerably by jurisdiction), restrictions on automatic or assisted-opening mechanisms, restrictions on certain blade shapes (some jurisdictions historically restricted specific styles), and location-based restrictions such as schools, courthouses, and government buildings, which frequently prohibit knives regardless of state-level carry law. Because these specifics change and differ so significantly by location, this guide intentionally does not state specific numeric limits as current fact for any particular state — verify with an official source for your location.
Assisted-Opening and Automatic Knives
Assisted-opening knives (like the Kershaw Leek, which uses a spring to complete an opening motion the user starts manually) are treated differently from true automatic knives (which open fully from a button press alone) in most jurisdictions, but a small number of state and local laws classify them similarly. This is one of the more frequently misunderstood areas of knife law and is worth specifically verifying if the knife in question uses any assisted mechanism.
Air Travel and TSA Rules
As of this writing, TSA prohibits all knives — including small folding pocket knives — in carry-on luggage on flights departing US airports. Pocket knives are generally permitted in checked luggage. International travel adds another layer: destination countries have their own import and possession rules that may be more restrictive than US law. TSA rules and international import rules can change, so checking current guidance before any trip involving a knife is the safer approach rather than relying on past experience.
A Practical Checklist Before Carrying
- Check your state's current blade length limit and whether it differs by county or city
- Confirm whether your knife's opening mechanism (manual, assisted, or automatic) is restricted in your area
- Identify location-based restrictions (schools, government buildings, certain private property) that apply regardless of general carry law
- If traveling, check both TSA guidance and any destination state or country's specific rules
- When uncertain, the more conservative choice (shorter blade, manual opening, checked luggage) avoids most legal risk