Pen guns are legal to own under federal law if you register the weapon with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) as a National Firearms Act item before you take possession. Because the design disguises a firearm as a writing instrument, the federal government treats it as an “Any Other Weapon” (AOW), which sits in a stricter regulatory category than an ordinary handgun. Federal approval is only half the picture, though. Several states ban disguised firearms outright, and in those states an approved federal tax stamp will not save you.
What Counts as a Pen Gun
A pen gun is a small-caliber, single-shot firearm built to look like a ballpoint pen. Most models chamber .22 LR, .25 ACP, or .32 ACP, and each round must be loaded manually. The whole point of the design is that a casual observer sees a pen. That deliberate concealment is what pulls pen guns out of the normal handgun rules and into the National Firearms Act.
Why the ATF Treats a Pen Gun as an “Any Other Weapon”
The National Firearms Act defines an “any other weapon” as, broadly, a concealable device from which a shot can be fired using the energy of an explosive. The statute carves out standard pistols and revolvers with rifled bores, which is why a regular handgun does not fall into the category.1Office of the Law Revision Counsel. 26 USC 5845 – Definitions A pen gun does not fit that carve-out. It is concealable, it fires a round, and it is disguised as something else entirely. The ATF’s NFA reference guide lists pen guns alongside cigarette-lighter guns, knife guns, and cane guns as textbook AOWs.2ATF. Chapter 2: What Are Firearms Under the NFA
The classification matters because standard handguns are regulated under the less restrictive Gun Control Act, while AOWs fall under the NFA with its registration, approval, and tracking requirements. Owning an unregistered pen gun is a federal felony, even if you legally own dozens of regular firearms.
How to Legally Buy One
Buying an NFA-regulated item is not like picking up a rifle at a sporting goods store. ATF has to approve the transfer before the item ever changes hands.
- Find the item through a Federal Firearms Licensee (FFL) who also holds a Special Occupational Tax (SOT) license for NFA items. Private sales are not an option.
- Submit ATF Form 4, either through the eForms system or on paper. The application requires your fingerprints, a passport-style photograph, and notification to your local chief law enforcement officer.3ATF. Chapter 9: Transfers of NFA Firearms
- Pay the transfer tax. As of 2026, the NFA transfer tax for an AOW is $0. Recent legislative changes eliminated the tax for all NFA firearms except machineguns and destructive devices. The registration requirement still applies in full. A $0 tax stamp is still a tax stamp.4Office of the Law Revision Counsel. 26 USC 5811 – Transfer Tax
- Wait for approval. As of February 2026, ATF’s average processing time for an individual eForms Form 4 was about 10 days; trust applications averaged around 26 days.5ATF. Current Processing Times
- Take possession only after ATF returns the approved form. Picking the item up early is a federal crime.
Every NFA firearm also has to carry permanent identifying markings on its frame, including the maker’s name, city, and state, visible without disassembly.6eCFR. 27 CFR 479.102 – Identification of Firearms The engraving must match what appears on your approved form.
Who Cannot Own One
Federal law bars several categories of people from possessing any firearm, and ATF will deny your Form 4 if you fall into one of them. The disqualifiers include:
- Anyone with a felony conviction, meaning any crime punishable by more than one year in prison
- Fugitives from justice
- Users of, or people addicted to, a controlled substance
- Anyone adjudicated mentally defective or committed to a mental institution
- People in the country unlawfully
- Anyone dishonorably discharged from the military
- People subject to a domestic violence restraining order
- Anyone with a misdemeanor domestic violence conviction
These categories come from the Gun Control Act and apply to all firearms.7ATF. Identify Prohibited Persons A prohibited person caught with a pen gun faces both NFA and Gun Control Act charges, which can stack.
Why Your State Law Matters More Than the Tax Stamp
Federal registration does not override state law. Several states ban disguised firearms outright, so an approved tax stamp is meaningless if your state has criminalized the weapon itself. Others regulate pen guns under concealed-weapon statutes, which may require a separate state permit or restrict where you can carry. Some sweep pen guns into broader prohibitions on “zip guns” or improvised firearms.
Because state rules vary so widely, the only safe approach is to check your specific state’s criminal code before you buy. Look for state definitions of “disguised weapon,” “zip gun,” and “any other weapon.” A pen gun that is perfectly legal in one state can be a felony 20 miles across the border. If you plan to travel with one, confirm the law in every state you’ll cross, not just your destination.
What Happens if You Skip the Process
The NFA lists several prohibited acts that most often catch pen gun owners: possessing an unregistered NFA firearm, possessing one that is not registered to you, transferring one without approval, and making one without prior ATF authorization.8GovInfo. 26 USC 5861 – Prohibited Acts Each is a separate offense.
A conviction carries up to 10 years in federal prison and a fine of up to $10,000 under the NFA’s penalty statute.9Office of the Law Revision Counsel. 26 USC 5871 – Penalties The practical fine ceiling is higher, because a separate federal sentencing statute allows fines up to $250,000 for individuals and $500,000 for organizations on any felony, and NFA violations qualify.10Office of the Law Revision Counsel. 18 USC 3571 – Sentence of Fine Any firearm involved in the violation is also subject to seizure and forfeiture.11Office of the Law Revision Counsel. 26 USC 5872 – Forfeitures
Those are federal consequences only. If your state also bans disguised firearms, state charges can run alongside the federal case, adding more prison time and additional fines.