Criminal Justice & the Rule of Law

The Legal Landscape of Ghost Guns and Potential Reforms

Eric Halliday, Rachael Hanna
Friday, March 19, 2021, 10:11 AM

The popularity of ghost guns has risen sharply in the past few years, especially during the coronavirus pandemic. What exactly are ghost guns, why does the Biden administration want to regulate them and what are the potential options for reform?

The Bureau of Alcohol, Tobacco, Firearms and Explosives Headquarters in Washington, D.C. (Flickr,; CC BY 2.0,

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The Biden administration is reportedly considering legal options, including executive orders and regulations, to curb the proliferation of ghost gunsuntraceable firearms often assembled in users’ homes with prefabricated components purchased online. If the administration takes legal action, it would be the latest change to a legal landscape that has been the subject of repeated bouts of litigation and legislative jockeying in recent years.

Understanding the mechanics of ghost guns is necessary context for the legal debates surrounding their regulation. Two factors distinguish ghost guns from conventional firearms. First, the moniker “ghost gun” derives from the fact that, unlike conventional firearms, these weapons are not manufactured with serial numbersthe primary mechanism of tracking firearms used by state and federal law enforcement. Second, rather than being manufactured in a factory and then purchased as complete weapons, ghost guns are typically assembled by buyers who purchase the components online and receive them at their homes. Numerous reports have documented how easy that assembly process is, with several experts comparing it to constructing Ikea furniture. The components shipped by manufacturers to individual buyers are often called 80 percent receivers; a receiver, or frame, forms the body of the weapon, while “80 percent” implies that the receiver is 80 percent finished, although the work required to complete the weapon varies based on the model or manufacturer. Other ghost guns can be manufactured entirely at home using a 3-D printer; in that case, all someone has to do is buy or obtain a blueprint online and print out the schematic. You can read more of Lawfare’s coverage on 3-D printed guns here.

Recently, ghost guns have exploded in popularity. Although no statistics are available to document exactly how many ghost guns are sold and assembled every year, the coronavirus pandemic has undeniably been good for the business of manufacturers. According to one report, more than a dozen different manufacturers of 80 percent receivers and similar components have reported shipping delays since March 2020 because of an overwhelming demand for their products. One manufacturer compared the craze for ghost guns to frenzied shopping on Black Friday, explaining that, like toilet paper and groceries, customers are stocking up on ghost guns to feel safe during a period of historic uncertainty.

Not surprisingly, ghost guns are increasingly popular with criminals, domestic extremists and others looking to act outside the law. Washington, D.C., police reported a 342 percent increase in seized ghost guns between 2018 and 2019, before the number of ghost guns more than doubled again in 2020. As of May 2019, 30 percent of firearms in the Bureau of Alcohol, Tobacco, Firearms and Explosives’s (ATF’s) central vault of seized illegal weapons were ghost guns. Further, several mass shooters have used ghost guns to murder their victims. In one infamous example, a boy used a ghost gun to murder three of his classmates in their high school in Santa Clarita, California. He had taken the gun from his father, who had obtained it after being ordered to give up his conventional firearms due to psychiatric issues.

The Biden administration’s intent to regulate ghost guns is a direct result of the popularity of ghost guns and their increased threat to public safety. To give context for these potential reforms, we provide an overview of the current state of the law as it relates to ghost guns before reviewing reforms under consideration at the federal and state levels.

Current Legal Landscape

At the heart of the current legal and policy debate over ghost guns is the fact that the ATF does not consider 80 percent receivers to be firearms under the Gun Control Act (GCA) of 1968. Among its many provisions, the GCA requires that any manufacturer or importer of a firearm mark that weapon with a unique, permanent serial number. Under 18 U.S.C. § 921(a)(3), a firearm is defined as “(A) any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive; (B) the frame or receiver of any such weapon; (C) any firearm muffler or firearm silencer; or (D) any destructive device.” In addition to banning the manufacture of firearms without serial numbers and criminalizing the possession of any firearms with altered or destroyed serial numbers, the GCA also prohibits certain classes of individuals from purchasing firearms, including minors and individuals convicted of felonies or misdemeanors involving domestic violence. Further, the statute requires that licensed gun sellers run background checks on potential buyers, deny weapons to anyone who falls into a disqualifying category and record the serial numbers of the weapons in any sale.

In addition to being the primary federal law enforcement agency tasked with enforcing the GCA, the ATF also has regulatory authority to interpret federal statutes and issue guidance to parties that come within its regulatory purview. As part of those responsibilities, the ATF issues “classification letters” in which it explains its “official position” on the regulatory status of firearms and related products. These letters are particularly useful for gun manufacturers and sellers, who can solicit the ATF’s opinion—typically by sending it physical models of the product in question—and thereby learn how the agency views a specific product before marketing and selling it.

Beginning in the early 1980s, the ATF explained in a series of classification letters that 80 percent receivers were firearms under § 921(a)(3) because they could easily be converted into functioning firearms, thereby satisfying that particular provision of the statutory definition. Its rationale was rooted in the temporal language of the GCA, namely, whether the receivers in question were “designed to or may readily be converted” to fire a projectile. In declaring that 80 percent receivers were in fact firearms under the GCA, the ATF pointed to the amount of time required to convert them into fully functioning firearms. For example, in a 1983 letter to a weapons manufacturer, the ATF classified an AR-15 receiver as a firearm under the GCA because a purchaser could transform it into a functioning rifle within 75 minutes. The ATF maintained that rationale through the mid-2000s; in 2004, it wrote another letter explaining that an 80 percent frame of a semiautomatic pistol was a firearm because the frame “could be completed in a minimal amount of time by a competent individual having the necessary equipment.”

Two years later, however, the ATF changed its thinking and stopped classifying 80 percent receivers as firearms, rooting its rationale on the mechanical characteristics of the receivers instead of the amount of time necessary to convert them into weapons. In a 2006 letter to a manufacturer, the ATF explained that receivers “must be completely solid and unmachined in the trigger/hammer recess area” in order to not be classified as firearms and did not discuss the amount of time necessary to convert them into weapons. Proceeding along that mechanical line of analysis, the ATF has since determined repeatedly that different variations of 80 percent receivers are not firearms because they lack certain “machining” characteristics—typically that the firing cavities have not been drilled to allow the exit of a fired bullet. The broad array of online tutorials on 80 percent receivers on websites like and explain how to easily complete that process using home tools. Because the ATF now does not classify 80 percent receivers as firearms, they fall outside the GCA, meaning that manufacturers do not have to inscribe them with serial numbers, record the identities of their customers, or run background checks on their customers to prevent sales to convicted felons, domestic abusers or other groups prohibited from owning firearms.

Of course, the federal government is not the only regulator of firearms in the United States. States have their own firearms laws, and some have taken a more aggressive approach on 80 percent receivers, but the severity of state laws varies even among those that have taken action. California and Connecticut, for example, require serial numbers on all firearms. New York, Massachusetts, Virginia and Washington all regulate undetectable guns—typically made with plastic from a 3-D printer and capable of not triggering metal detectors—but do not currently require serial numbers. A complete list of current state laws in this area can be found here. The bottom line is that ghost guns are unregulated at the federal level and in most states, but different state laws create a patchwork of regulation for gun manufacturers and purchasers to navigate.

Notable Litigation

In response to the Santa Clarita high school shooting, the state of California, several gun control advocacy groups, and the parents of two children killed by shooters wielding ghost guns filed suit against the ATF and the Justice Department in the Northern District of California in September 2020. They argue that the ATF’s failure to classify ghost guns as firearms and thus to subject them to appropriate regulation contravenes the GCA and is arbitrary and capricious. As the lead plaintiff, California rests its position primarily on the ATF’s interpretation of 18 U.S.C. § 921(a)(3) prior to 2006. The state believes that ATF’s abandonment of its temporal test “that looked at the speed and ease with which a receiver or frame could be converted into an operable firearm” in favor of a “machining operations” assessment that looked at the remaining assembly tasks was done without justification.

California argues that the ATF’s now-abandoned temporal analysis was consistent with the GCA’s text, which states that “‘firearms’ include, not only fully functional weapons, but also receivers and frames ... that are ‘designed to or may readily be converted’ into functional weapons.” When the ATF adopted its machining operations assessment, it did not provide a justification for abandoning the temporal test and adopting this new analysis; California argues that this failure to explain was arbitrary and capricious in violation of the Administrative Procedure Act (APA).

As evidence of the public safety threat unregulated ghost guns pose, California pointed to former ATF Acting Director Thomas Brandon’s acknowledgment that ghost guns that can be easily assembled should be classified as firearms. In the new deregulatory environment, ghost gun manufacturers now sell 80 percent receivers and frames that can be converted to operable firearms “in under 15 minutes.” And the ATF admits in its own guidance on ghost guns that the inability to trace ghost guns—because they lack serial numbers and their manufacture and purchase are not registered—“hinders crime gun investigations and jeopardizes public safety.” Furthermore, the lawsuit catalogs the mass proliferation of ghost guns in recent years, as well as the rising number of criminal cases around the country that involve such weapons.

Consequently, California alleges that it has suffered concrete harm from the ATF’s refusal to regulate ghost guns due to the proliferation of ghost guns in the state and the subsequent increased costs of policing and difficulty in enforcing its own firearms laws.

The lawsuit urges the court to find that the ATF’s “Ghost Gun Guidance” constitutes a binding rule, namely that 80 percent receivers and frames do not constitute firearms under the GCA; that this binding rule is arbitrary and capricious because it was made without going through the administrative rule-making process the ATF is obligated to follow under the APA; and that the ATF’s current rule holding ghost guns outside the scope of the GCA contravenes the text of the statute and is therefore unlawful. Most importantly to its argument, California claims that the ATF failed to consider important aspects of the consequences of failing to regulate ghost guns when it issued its “Ghost Gun Guidance,” such as whether the lack of regulation would contribute to a proliferation of untraceable firearms. Consideration of important aspects relevant to the agency’s decision is a required part of the rule-making process under the APA.

In a similar lawsuit, the cities of Syracuse, New York; San Jose, California; Chicago, Illinois; and Columbia, South Carolina, have sued the ATF and the Justice Department in the Southern District of New York, again over the ATF’s decision not to subject ghost guns to the GCA regulatory scheme. Like California, these cities claim that the ATF changed its classification of ghost guns to no longer be firearms in 2006 without justification and that its current binding position is arbitrary and in contravention of the GCA.

The key issues at stake in these cases are whether the ATF’s “Ghost Gun Guidance” constitutes an interpretive rule or policy guidance, which is not subject to the APA’s procedures for rule-making, and whether the ATF’s interpretation of the GCA to not include ghost guns as firearms was arbitrary and capricious and in contravention of the GCA.

However, before reaching these issues, California and these city plaintiffs have to clear the hurdle of standingthe doctrine allowing only plaintiffs connected to the underlying controversy to bring suit in court. To do so, they must demonstrate that they have suffered concrete injury, the harm suffered was caused by the ATF’s failure to regulate ghost guns, and the harm can be redressed by the relief sought, which in this case is the ATF regulating ghost guns as firearms under the GCA. In its motion to dismiss the California lawsuit, the ATF and the Justice Department argue that the state has failed to demonstrate that it has suffered an increased cost of policing due to a handful of crimes that involve ghost guns and thus has failed to demonstrate suffering a concrete injury. Moreover, the government argues that any harm California might have suffered was not caused directly by the ATF’s lack of ghost gun regulations. By that, the government means that the chain of causation from (a) a lack of regulation to (b) more ghost gun manufacturers entering the market to (c) prohibited persons acquiring such guns, and then to (d) those persons using such guns in the commission of crimes is too attenuated to survive under federal standing doctrine. Likewise, the government argues that the harm California alleges cannot be redressed by the regulation sought because the harms were “caused by the independent, criminal acts of third parties.” The plaintiffs in both lawsuits also might be time-barred with respect to their claims over the ATF’s 2006 change in interpretation of the GCA; 28 U.S.C. § 2401(a) imposes a six-year statute of limitation on all APA claims.

Should the courts address the merits of the arbitrary and capricious claims, the plaintiffs likely face an uphill battle, as agency interpretations of their own statutes—here the GCA—are entitled to considerable deference when being reviewed by the courts.

Potential Reforms

Federal Legislation

Potential reforms available to elected officials and policymakers flow along two axes: legislative versus regulatory, and federal versus state. Of those options, federal legislation would be by far the most sweeping and comprehensive option. By amending the GCA to specifically cover 80 percent receivers and other gun components, Congress could impose nationwide standards that would compel the ATF to regulate ghost guns and fill the vacuum left by most state legislatures.

Several Democratic lawmakers have recently introduced bills designed to do exactly that, although the language and provisions of each bill vary somewhat. For example, 15 Democratic senators have co-sponsored the Untraceable Firearms Act, which would extend the GCA definition of firearms to cover 80 percent receivers and gun kits purchasable online. It would also ban the possession of untraceable ghost guns and firearms that could be modified to pass through metal detectors without setting off the alarms. On the House side, Reps. Brad Schneider and Adriano Espaillat have introduced the Ghost Guns Are Guns Act, which would amend the GCA to define a firearm to include “any combination of parts designed or intended for use in converting any device into a firearm and from which a firearm may be readily assembled” but does not ban the possession of ghost guns. Another bill, the Trafficking Reduction and Criminal Enforcement (TRACE) Act, introduced by Rep. Mike Quigley, would similarly amend the GCA definition of a firearm; it would also implement several broader gun safety provisions, like ordering the ATF to promulgate regulations requiring that all gun manufacturers inscribe weapons with a second serial number visible only in infrared light.

Though Democrats have narrow control over both houses of Congress, the feasibility of passing ghost gun legislation depends on the typical factors that affect the success of proposed bills: the actual text of the different proposals, the enthusiasm among the Democratic caucus to prioritize such a statute and the potential willingness of Republicans to cross the aisle on a typically highly partisan issue. That last factor is the most crucial in light of the Senate’s legislative filibuster, which can be defeated only by 60 senators voting in favor of a bill. Therefore, unless the political landscape changes dramatically in the near future, federal ghost gun legislation remains unlikely.

State Legislation

As discussed previously, several states have already passed legislation addressing ghost guns in some capacity, and several others are considering either strengthening their existing laws, like New York, or passing new ones, like Maryland. Even so, the majority of states have no legislation addressing ghost guns, nor is there any sign of a groundswell of national enthusiasm for ghost gun regulations. Like almost all aspects of the gun control debate, the treatment of ghost guns is a fiercely partisan issue, making it unlikely that state legislatures in Republican-controlled states will take up proposals to regulate ghost guns.

Thus, the current patchwork of state-by-state regulation will likely remain, even if a handful of additional states pass ghost gun legislation. Although the illegality of ghost guns in certain states will almost certainly deter purchasers with a legitimate, recreational interest in firearms, it is unlikely to have the same effect on would-be criminals, domestic extremists and other bad actors. Further, the effect of ghost gun laws on the state level will likely be weakened by the ease of legally purchasing such weapons in other states and transporting them across state lines—a dynamic with conventional firearms that currently bedevils law enforcement officials in states with stricter gun laws.

ATF Regulation

Given those political difficulties, it is not surprising that many advocates of ghost gun regulation have concentrated on the ATF as the most likely avenue for reform. In fact, because the ATF can comprehensively regulate ghost guns by classifying 80 percent receivers and other comparable components as firearms, such regulation would be easier to achieve than other policy goals on the gun control agenda.

The ATF is well within its regulatory purview to change its definition of a firearm. The APA allows administrative agencies several different options to promulgate new regulations or retract existing ones; some (like formal rule-making) are quite rigorous and drawn out, but the ATF may be able to avoid the more onerous paths and immediately issue a new classification letter in response to a manufacturer of 80 percent receivers. The ATF did not announce its change from a temporal analysis to a mechanical analysis through formal, or even informal, rule-making, which suggests that the agency viewed the change as a change to its interpretation of the GCA. Agency interpretations of their statutes are not subject to the APA’s rule-making procedural requirements. Rather, it announced no formal review process whatsoever and simply changed its responses in classification letters to manufacturers. Several members of Congress and advocacy groups have called on the ATF to revisit its understanding of “firearm” under the GCA to include ghost guns, and even the agency’s former acting director, Thomas Brandon, said that he urged his superiors in the Justice Department to make such a change in 2019, but to no avail.

Importantly, President Biden could not make this regulatory change himself through an executive action, but he and other officials in his administration could certainly direct ATF officials to change the regulatory regime.

Despite the ease with which the ATF could revise its approach toward ghost guns, any such decision would likely face lawsuits that would mirror those currently being brought by California and Syracuse. Opponents of ghost gun regulation could bring suit arguing that the ATF’s change was itself arbitrary and capricious, in violation of the APA. In fact, if manufacturers of 80 percent receivers joined those lawsuits, as they almost certainly would, they would probably clear the standing hurdles currently facing the pro-reform plaintiffs, as those manufacturers would be facing economic harm (due to decreased sales and the costs of compliance) as a result of increased regulation. Notwithstanding those obstacles, new ATF regulations are by far the most feasible avenue for meaningful reform on ghost guns.

Regulation by State Attorneys General

Finally, many state attorneys general play a regulatory role in addition to their law enforcement responsibilities, and several have already taken steps to further regulate ghost guns. Although statutes vary from state to state, some state attorneys general are endowed with the ability to opine on whether certain weapons or components fall within the ambit of state gun control laws. For example, in 2019 Pennsylvania Attorney General Josh Shapiro issued a legal opinion declaring that 80 percent receivers were firearms for the purposes of the state’s Uniform Firearms Act. On the basis of that opinion, Pennsylvania state police then announced that they would treat 80 percent receivers as firearms and enforce the law accordingly. A Pennsylvania state judge issued a preliminary injunction three weeks later, however, ruling that plaintiffs suing to block the state’s revised definition of “firearm” raised a legitimate point in arguing that the state police’s new policy was too vague. That litigation is ongoing.

Shapiro’s decision demonstrates another possible avenue for ghost gun regulation, but regulation by attorneys general faces both the political difficulties inherent in passing legislation and the added obstacle of legal challenges against their decisions’ underlying rationale. Although this hybrid model could be useful in bypassing state legislatures, its success will depend on the legal strength of each attorney general’s position and the reception it receives in state courts.

Eric Halliday is a graduate of Harvard Law School, where he was Co-Editor in Chief of the National Security Journal. He holds a B.A. in Political Science and Italian Studies from Tufts University.
Rachael Hanna is a recent graduate of Harvard Law School.

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