Are Ghost Guns Illegal? Federal Rules, State Bans, and Penalties

Ghost guns are not automatically illegal. Under federal law, you can build a firearm at home for your own use without a serial number, a license, or registration, as long as you are legally allowed to own a gun and you are not making it to sell. What is illegal is buying an unfinished frame or parts kit from a dealer without a background check, selling a homemade firearm without going through a licensed dealer, possessing one if you are a prohibited person, and, in roughly 16 states, possessing an unserialized firearm at all.

Federal Law Allows Personal Builds

Federal law does not require a home builder to obtain a serial number, apply for a license, or register the finished weapon. The ATF says directly that “you do not have to add a serial number or register the PMF if you are not engaged in the business of making firearms for livelihood or profit.”¹ A privately made firearm, in ATF terms, is one completed or assembled by someone other than a licensed manufacturer and without a factory serial number.

The threshold between hobby and crime is intent to profit. Federal law defines being “engaged in the business” as devoting time and labor to dealing in firearms as a regular course of trade, with the principal objective of earning money through repetitive purchases and resales.² Making a rifle for deer season or a pistol for the range does not cross that line. Producing firearms in volume with the intent to sell them does, and it requires a federal firearms license, serialization of every unit, and sales conducted through the regulated process.

The 2022 ATF Rule and the 2025 Supreme Court Decision

In 2022, the ATF finalized Rule 2021R-05F, which redefined what counts as a regulated firearm at the point of sale. A parts kit designed to be readily assembled into a working weapon is now a “firearm” for regulatory purposes, and a partially complete frame or receiver falls under the definition of “frame or receiver” when it is designed to, or can readily be, finished into a functional part.³ The ATF can look at any jigs, tools, instructions, or marketing sold alongside the item to decide whether it qualifies.

The rule’s obligations fall on licensed dealers, not on the person at a workbench. A federal firearms licensee selling an unfinished frame or a kit must engrave a serial number on it, run the buyer through the National Instant Criminal Background Check System, and record the sale on ATF Form 4473 with “privately made firearm” noted.³ For buyers, the practical result is that ordering an 80% frame or a build kit online now looks a lot like buying a completed handgun: identification, background check, paperwork.

In March 2025, the Supreme Court upheld the rule 7–2 in Bondi v. VanDerStok. Justice Gorsuch, writing for the majority, held that at least some weapons parts kits are “weapons” that meet the Gun Control Act’s “readily converted” standard, and that partially complete frames and receivers fit naturally within the statute.⁴ The Court rejected only the broadest facial challenge and left room for future cases arguing that a specific product falls outside the rule.

Fully Plastic Guns Are Illegal Under Federal Law

A separate federal statute, 18 U.S.C. § 922(p), makes it a crime to manufacture, possess, sell, or transfer a firearm that a walk-through metal detector cannot pick up. Every firearm must be at least as detectable as a “Security Exemplar” containing 3.7 ounces of stainless steel in the shape of a handgun, and major components like the barrel, slide, and frame must produce an accurate image on an airport-style X-ray machine.²

This is the provision that directly reaches 3D-printed firearms. A gun printed entirely from polymer with no metal in it violates the statute regardless of whether anyone stamped a serial number on it. Home builders using printed frames have to add enough metal to clear the detection threshold, and the rule applies the same way to hobbyists as to manufacturers.

Prohibited Persons Cannot Legally Build or Possess Any Firearm

Everything above assumes you can legally own a gun. Federal law bars several categories of people from possessing any firearm, and the absence of a serial number does not create a loophole:

Anyone convicted of a crime punishable by more than one year in prison
Fugitives from justice
Unlawful users of, or people addicted to, controlled substances
People adjudicated as mentally defective or committed to a mental institution
People unlawfully in the United States, and most nonimmigrant visa holders
People discharged from the military under dishonorable conditions
People subject to certain domestic violence restraining orders, or convicted of a misdemeanor crime of domestic violence

These prohibitions apply to privately made firearms in the same way they apply to any commercial handgun or rifle.² A prohibited person caught with a ghost gun faces the same federal charge as one caught with a store-bought pistol.

State Laws Are Where Most Bans Live

About 16 states have passed their own ghost gun laws, and they do not all look alike. Some require anyone who builds a firearm to apply for a state-issued serial number and engrave it into the frame before assembly. Others prohibit possessing an unserialized firearm outright, regardless of when it was made. A few ban the sale of unfinished frames and receivers entirely. Several go after the digital side, criminalizing distribution of the files used to 3D-print firearm components, and some prohibit 3D-printing firearms at all.

Several states have adopted detectability rules that meet or exceed the federal Undetectable Firearms Act, specifically banning firearms made entirely of plastic. State-level serialization programs typically come with filing fees and deadlines, and missing them can produce criminal charges independent of any federal issue.

Because the rules differ so sharply, a firearm that is legal in one state can be a felony to carry into the next. Anyone considering building, buying, or moving with an unserialized firearm should confirm the current law in their own state before acting.

Selling or Giving Away a Homemade Firearm

You cannot hand a homemade firearm to another person the way you might lend a tool. A transfer has to go through a federal firearms licensee. The dealer must engrave a serial number on the firearm within seven days of taking it into inventory, or before transferring it to the buyer, whichever comes first, and the buyer must pass a background check before taking possession.³

Building firearms with the primary purpose of selling them, without a license, is a federal crime. The ATF distinguishes between someone who occasionally sells a firearm from a personal collection and someone who repeatedly builds and sells to earn money. The first is a hobbyist; the second is an unlicensed dealer, and the sentencing exposure runs to years.

Estate transfers are less clearly regulated. When a gun owner dies and leaves behind unserialized firearms, executors face rules that are more explicit for registered NFA weapons than for ordinary privately made firearms. Working with an attorney and a licensed dealer to serialize and transfer estate firearms through the proper channel is the safe route.

Penalties

The general federal penalty for willfully violating the Gun Control Act runs up to five years in prison and a fine.⁵ That covers offenses like dealing without a license or violating the ATF’s kit and frame rules. Other exposures escalate from there:

Firearms trafficking, a standalone offense created by the Bipartisan Safer Communities Act of 2022, carries up to 15 years, or 25 years if tied to a felony, drug crime, or terrorism.⁶
Straw purchasing, meaning buying for someone else or lying on the purchase form, carries the same 15-year maximum under the same act.⁶
A prohibited person in possession of any firearm, ghost gun included, faces up to 15 years under federal law.
Possessing an unregistered short-barreled rifle, silencer, or other NFA weapon carries up to 10 years.¹

State penalties stack on top of federal ones. In states that ban unserialized firearms, simple possession can be a felony, with prison time, fines, and a permanent loss of firearm rights. Some judges have treated the use of a ghost gun as an aggravating factor at sentencing.

A federal firearms conviction also triggers forfeiture. Under the Bipartisan Safer Communities Act, anyone convicted of trafficking or straw purchasing must forfeit property derived from the offense and property used to facilitate it.⁶ Restoring federal firearm rights after a conviction is difficult. As of early 2026, the Department of Justice has published a proposed rule that would create a rights-restoration process under 18 U.S.C. § 925(c), but no active application process is yet in place.⁷

Crossing State Lines

Federal law offers a limited safe-passage protection. Under 18 U.S.C. § 926A, someone who may lawfully possess a firearm in both the origin and destination states can transport it across state lines, even through states with stricter laws. The firearm must be unloaded, and neither the gun nor ammunition can be readily accessible from the passenger compartment; in vehicles without a separate trunk, the firearm has to be in a locked container other than the glove box or center console.⁸

The statute does not distinguish serialized from unserialized firearms, but it only protects you while you are actually passing through. Stop and do anything more, and the local law takes over. Air travel adds its own layer: the TSA requires firearms to be unloaded, declared at the ticket counter, and transported in a locked, hard-sided case as checked baggage.⁹ TSA rules do not address serial numbers, but landing in a state that bans unserialized firearms with one in your bag creates the same criminal exposure as driving one in.

1
Bureau of Alcohol, Tobacco, Firearms and Explosives. Privately Made Firearms
2
Office of the Law Revision Counsel. 18 USC 922 Unlawful Acts
3
Bureau of Alcohol, Tobacco, Firearms and Explosives. Final Rule 2021R-05F Definition of Frame or Receiver and Identification of Firearms
4
Supreme Court of the United States. Bondi v VanDerStok No 23-852
5
Office of the Law Revision Counsel. 18 USC 924 Penalties
6
U.S. Congress. Bipartisan Safer Communities Act Text
7
U.S. Department of Justice. Federal Firearm Rights Restoration Under 18 USC 925(c)
8
Office of the Law Revision Counsel. 18 USC 926A Interstate Transportation of Firearms
9
Transportation Security Administration. Transporting Firearms and Ammunition