Are you ready for what it takes to stop ghost guns?

In the summer of 2024, former Army National Guard member Andrew Scott Hastings spent a sweaty afternoon carefully packing boxes with parts he made using his 3D printer. These weren’t novelty figurines or replacement Ikea pieces. The boxes were instead filled with a handful of homemade firearm lower receivers and more than 100 “switches,” small devices capable of converting a semiautomatic gun into a fully automatic weapon. Their intended recipients, federal prosecutors allege, were al-Qaida operatives.

Months later ATF agents busted two men in Colorado Springs for allegedly using 3D printers to churn out hundreds of illegal machine gun conversion devices as a part of a DIY black market. To avoid detection the duo allegedly stuffed their products into Lego boxes and shipped them to buyers across the country.

There was, however, no recent case that thrust 3D-printed guns — a type of untraceable “ghost gun” — back into the public consciousness quite like the killing of UnitedHealthcare CEO Brian Thompson in December 2024. Suspected gunman Luigi Mangione, then 26, allegedly shot Thompson outside a Manhattan hotel using a partially 3D-printed Glock-style frame and a 3D-printed silencer, otherwise known as a suppressor, the latter of which would otherwise require months of federal paperwork to obtain legally.

3D-printed guns have been around for over a decade. Cody Wilson, a self-described crypto anarchist, created the first functional printed firearm in 2013, and lawmakers and courts have tussled with how to rein them in ever since. Those efforts largely targeted the gun files themselves and the websites that hosted them, but courts have (with some exceptions) repeatedly treated gun code as a form of protected speech, frustrating gun control advocates at every turn. Though many states have passed laws specifying who can print or share gun files, they are notoriously difficult to actually enforce.

Today, almost anyone with a printer, internet access, and enough patience can browse file-sharing sites and attempt to make their own gun.

But a new volley of legislation progressing in California and New York aims to shake up that stalemate by moving regulation from the files to the machines themselves, requiring 3D printers to employ blueprint scanning “print blocker” software that, in theory, would detect gun files and stop the print before it starts. It’s essentially taking the long-running debate over online content moderation and translating it to the physical world.

The problem is, neither New York nor California specifies what the blocking technology must actually look like. That flexibility gives the printing industry and technologists more time and freedom to experiment with different technical approaches, but it simultaneously leaves critics on edge — unsure whether a relatively contained gun control measure could eventually evolve into something closer to a broad infrastructure for file surveillance.

The first rumblings of blocking technology legislation emerged in Washington state earlier this year with HB 2321, which would have required all 3D printers sold in the state to come equipped with “firearm blueprint detection algorithms,” alongside a database of prohibited guns and components maintained by the state’s attorney general. The bill faced immediate pushback from makers and industry experts who argued it would needlessly sweep up legitimate non-firearm parts in its net and drive hobbyists away from 3D printing altogether. It died in committee, but the bill’s skeleton would go on to form the backbone of ongoing efforts in California and New York.

California’s AB 2047 would require the state’s Department of Justice to maintain an approved roster of 3D printer makes and models equipped with certified firearm-blocking technology. The DOJ would retain the ability to update and alter the requirements for that roster over time. A recent addition to the bill provides an exception for Hollywood, which regularly uses 3D printers to make gun props. If passed, manufacturers who want to sell printers in the state would have to attest that they have implemented a firearm detection algorithm approved by the government in each make and model they submit — though the details of exactly what that scanning tech entails are left unspecified.

What is clear is that any printer sold after March 1st, 2029, that doesn’t appear on the approved list would be illegal to sell in the state, with civil penalties of up to $25,000 per violation. Hackers or tinkerers who knowingly disable or circumvent the blocking software on an approved printer, meanwhile, could face misdemeanor charges and potential jail time. The bill passed the California Assembly on May 26th but still needs Senate approval and a signature from Gov. Gavin Newsom before becoming law.

A similar effort in New York was signed into law in late May. Over the past few months, Gov. Kathy Hochul has described 3D-printed gun parts as the “fastest growing gun safety threat in the country” and has even invoked the image of gun makers supposedly printing parts on their kitchen tables. On May 22nd, the state legislature finalized the FY 2027 budget, which includes a section mandating gun-blocking technology on printers sold in the state, among a handful of other anti-ghost gun provisions. New York’s law goes further by applying to CNC machines and making it a felony to distribute gun files to anyone who isn’t a licensed gunsmith.

Like in California, the New York law requires every 3D printer sold in the state to include software that blocks it from printing a firearm or firearm component. And like in California, the exact specifications of what constitutes an acceptable firearm blueprint detection algorithm remain exasperatingly vague, left for a panel of experts to determine at a later date.

New York specifically calls for the formation of a working group of tech and gun policy experts who will convene to make “minimum safety standards” this proposed blocking technology would need to meet to comply with the mandate. Crucially, the same group has to admit if they find this kind of tech is “not technologically feasible.” In other words, the law as written advocates in favor of technology that experts still aren’t really sure will actually work.

“We’ve already gone after the iron pipeline,” Hochul said in a March press conference in reference to ghost guns. “Now we’re going after the plastic pipeline.”

Hochul’s office declined to comment about how they intended to enforce the law.

Supporters argue this on-device software is needed to close an enforcement gap that lets those with felony convictions and others access weapons they otherwise couldn’t legally obtain. Laws are already on the books in dozens of states prohibiting the unlicensed manufacturing of 3D-printed guns, but those are nearly impossible to enforce in practice, since the printing occurs in private. Mandatory blocking technology installed on printers would, in theory at least, address that problem by stopping the job before its gun part is ever completed.

In a private video meeting with members of the 3D printer industry obtained by The Verge, academic experts in gun policy and printer software said it’s possible printer manufacturers could have various paths to compliance with the proposed laws. Rutgers University professor and New Jersey Gun Violence Research Center director of research Daniel Semenza said legislators aren’t necessarily seeking perfection. The mandates instead are intended to add friction to the gun printing process so it isn’t trivially easy for a novice with little technical know-how to manufacture weapons. In other words, the most advanced, potentially privacy-invasive blueprint scanning option might not be needed to avoid running afoul of the authorities.

“The goal is to raise the bar so you can’t be a curious kid in your bedroom who is able to download a file, press print, and then you have the gun or 3D-printed part,” Semenza said.

“The unfortunate truth is that it doesn’t stop every person from [printing a gun],” Semenza added.

For such a system to actually work, approved printers would have to scan every file a user presents, regardless of whether that person has the slightest interest in guns.

One easier-to-achieve approach would check print jobs against a database of hashes — unique digital fingerprints tied to known gun or gun component files — and block the print if there’s a match. The method is similar in concept to how tech platforms prevent the spread of child sexual abuse material by checking uploads against a database of known hashes maintained by the National Center for Missing & Exploited Children.

That may sound straightforward, but critics say the fundamental way 3D printers work on a mechanical level would make it toothless. Any modification to a print file’s source code, even a trivially small one, produces a different hash, potentially bypassing detection while leaving the printed object functionally unchanged. Hashing only works when exact copies are involved.

The second, more effective and more controversial approach involves so-called predictive code scanning. Companies like Spain-based Print&Go claim their AI tools can analyze a CAD file before it prints and predict with a high degree of accuracy whether the resulting object would constitute a prohibited gun or gun component. This method goes beyond simply comparing exact fields listed on some databases. It in effect attempts to predict what a printer will spit out.

“Besides just relying on a list of known guns, the self-trained detection method can spot new or modified ghost guns STL files that aren’t in the database yet,” Print&Go writes on its website.

That second approach in particular has drawn backlash. And gun lovers aren’t the only ones bristling at the idea of mandating gun file scanning on printers. An outpouring of hobbyists, independent makers, and right-to-repair advocates worry this type of on-device surveillance, even if well intentioned, risks fundamentally usurping the open-source, DIY ethos of 3D printing. Still-evolving file-scanning technology, some tell The Verge, could misidentify everyday objects like hoses or Nerf toys as possible guns. Worse still, makers say a no-print database that earnestly starts with gun files could be abused and expanded by corporate entities looking to enforce IP and copyright protections.

Tech ostensibly sold to stop shootings, in other words, may eventually prevent a maker from printing their own car part or novelty lamp.

“It’s all a big ball of stupid and I hate it,” Seattle Makers founder Jeremy Hanson told The Verge. Hanson, who has been involved in various maker spaces since childhood and currently works to provide tools, workspaces, and know-how to other creators, worries efforts to implement blocking technologies into printers could stymie future makers. Hanson and his colleagues pushed back against the Washington requirement, helping lead to its eventual defeat. Another, weaker bill that makes it illegal for anyone intending to manufacture unlicensed firearms to possess or share gun files was signed into law in late March.

“I see it as a toe in the door on controlling manufacturing,” Hanson added. “It’s already illegal to have a homemade unlicensed gun, and this technology [3D printing] isn’t efficient for manufacturing firearms. But it’s a good way to sell it to the public. The actual mechanism for control is vague and remains undetermined.”

Other makers worry applying this form of “censorware” to printers could dissuade future creators from experimenting with the tech for fear of breaking a law. Popular 3D printer enthusiast and YouTuber Loyal Moses imagines a future where 3D printing “moves to the basement” and is viewed with a veneer of shady criminality. Older, pre-scanning “dumb” printers would become sought-after gray-market commodities.

More broadly, makers worry that scanning software could push 3D printing away from its open-source roots and toward the kind of closed, tightly controlled walled gardens that have come to define smartphones and social media. And while supporters of the bills argue those hypothetical, slippery slope concerns may needlessly impede necessary action against guns, critics like Electronic Frontier Foundation associate director of technology policy and research Cliff Braun note the mechanism at play could mark a point of no return.

“There’s a difference between a slippery slope saying someone is maybe going to do something in the future and literally building the infrastructure to do that,” Braun told The Verge. “And that’s what these bills do.”

This momentum around blueprint scanning reflects a new reality, says Nick Suplina, formerly the senior vice president for law and policy at gun violence prevention group Everytown for Gun Safety. Everytown is a major supporter of the legal efforts across the country and has testified in numerous public hearings defending them. Suplina said gun printing technology has “leapt forward,” a claim that is supported at least in part by the increasingly sophisticated-looking weapons found in police raids around the world.

These aren’t the volatile single-shot peashooters of the mid-2010s. The FGC-9, one of the more popular gun designs online, fires multiple 9mm rounds without breaking, and its core components can be built with a printer costing as little as $200. (FGC stands for “fuck gun control.”) Their use is also no longer limited to gun nerds with too much time on their hands. The FGC-9 has been used by rebel forces fighting against Myanmar’s military junta and seized from neo-Nazi cells in Europe.

And while fully or even mostly 3D-printed guns in the US are a tiny fraction of the millions of firearms in circulation, their numbers are increasing. In 2021, the New York Police Department said it recovered just a single 3D-printed gun. In 2024, that number jumped to 109. A separate 2024 Everytown report found similar results in 20 other cities. In Seattle, 3D-printed guns recovered from crime scenes increased from 34 in 2021 to 84 in 2024. In Detroit, recoveries increased from 21 to 57 during that same period.

This increase in 3D-printed gun recoveries comes as recoveries of “ghost guns” generally, which can be made from an assortment of non-3D-printed parts, have trended downward in recent years. Experts link the recent decline of non-3D-printed ghost gun seizures to 2022 federal rules requiring serialization of so-called “80 percent” DIY gun kits. 3D-printed guns, which can skirt around these new serial number requirements, the theory goes, are potentially filling that market gap for criminals.

Citing that momentum, Suplina said it’s time to pump the brakes on 3D-printed guns before they reach escape velocity.

“What we’re seeing is that typical pattern like you would with an outbreak,” he said. “Small numbers doubling year over year, to a point where we realize that action right now is critical or else we’re going to have an unmanageable problem very, very soon.”

Wilson, who has fought back against 3D-printed gun regulations since the technology’s inception, pushes back on that framing. “You’re going from statistically negligible to statistically identifiable,” Wilson told The Verge. “But that doesn’t mean it’s overtaking a meaningful share of criminal gun activity yet.”

WWhen asked how file-scanning tech would work on 3D printers, supporters repeatedly point to the success paper printers have had in preventing the proliferation of counterfeit money. Since the mid-1990s, paper printers have been programmed to detect a hidden pattern embedded in real banknotes and refuse to reproduce them. This process started with $100 notes and eventually expanded to include all denominations other than $1 bills. For the most part, it’s been a success.

“This is the analogy here,” Suplina said of preventing paper printers from making counterfeit money. “You go to the source, you stop the firearms from being printed on the printer …That is the way to stop this problem in its tracks.”

Print&Go says it uses AI and pattern matching to analyze print jobs and compare files against a maintained database of known firearms and components. If the system flags a high enough likelihood of a weapon part, it stops the print. The company says its software can be installed directly into a printer’s firmware, meaning the protection works even when the printer isn’t connected to the internet.

John Amin, Print&Go’s founder, told The Verge his company began developing the current software after they heard about students bringing 3D-printed guns to school. The paper printer comparison was used as evidence something like this was potentially in reach for 3D printers.

“The technology is developed to protect, not to piss off,” Amin said. In a follow-up email, Amin told The Verge his company is “collaborating actively” with both Everytown and the New York governor’s office.

But the comparison to anti-counterfeiting tools in paper printers only goes so far. In that case, printers are looking for known banknote identifiers and preventing those from being printed, and the identifiers on the bills are designed explicitly to be detectable. Most people never realize printers have this software because it’s so specifically tailored to forged currency. Successfully stopping prints of gun parts, on the other hand, might require targeting such a broad range of shapes as to block completely unrelated prints.

Makers and technologists told The Verge they were skeptical of how well the scanning tech could work in practice. Braun describes the process in general as “censorware” and questions whether average consumer printers have enough processing power to run meaningful geometric analysis locally. If they don’t, he said, manufacturers may have no choice but to route files through third-party cloud servers — raising the prospect of slower print times, false positives, and exposure of users’ private files to the printer manufacturer or potential hackers. Even if those problems are solved, Braun argues, bad actors will simply make incremental modifications to their files to slip past detection.

“There’s just an infinite number of ways for people to sidestep this,” Braun said. “And a natural consequence of making this work is that you’re going to start preventing people from printing things they want to print just to fix their household appliances.”

Amin, meanwhile, said his company’s false positive rate is low and continually improving but nonetheless admitted some errors would inevitably occur.

“Perfect systems don’t exist,” he said.

Past efforts to limit the proliferation of firearm files online have fallen short for two closely related but distinct legal reasons: platform protection under Section 230 of the Communications Decency Act of 1996 and First Amendment protections for the code itself. Section 230 famously absolves platforms from liability for content uploaded by their users — the same reasoning that has shielded gun marketplaces like Armslist.com (the so-called “Craigslist of Guns”) from negligence suits brought by gun violence victims, and that prevents file-sharing sites like Thingiverse or Printables.com from being inundated with lawsuits when users upload gun files.

Many of those repositories voluntarily remove gun files anyway under their terms of service. Thingiverse, for example, recently agreed to implement AI scanning and human review of flagged uploads after Manhattan DA Alvin Bragg sent a letter documenting gun files still appearing on the platform despite its long-standing prohibition.

The question of whether gun code is also protected speech is even more complex, and still in dispute. Sites like DEFCAD and Wilson’s Defense Distributed, whose explicit mission is to share gun files, have had to argue in court that restricting 3D-printed gun files violates the First Amendment. Courts haven’t been entirely clear on that issue.

In February, the Third Circuit upheld a New Jersey ban on sharing 3D-printed gun files, ruling that “purely functional” computer code doesn’t carry the same First Amendment protections as expressive code, and that Defense Distributed had failed to demonstrate its files fell into the protected category. Supporters of the code-as-speech argument have long held that all computer code, at a fundamental level, should be considered a form of expression. This ruling was interpreted by legal experts to have narrowed that understanding.

“These files are not expressive speech, they’re purely functional code that leads to illegal lethal weapons in the wrong hands,” said Suplina.

Wilson, whose company sued the New Jersey attorney general over enforcement of the ban, told The Verge he thinks the issue of whether or not code is speech will likely wind up before the Supreme Court.

Legal battles over blueprint scanning are primarily taking place in New York and California, but passage anywhere could have ripple effects nationwide. If a larger state like California passes its bill, Braun said manufacturers like Bambu Lab or Prusa Research may simply opt to include scanning software on all new models regardless of where they’re sold, rather than maintain separate product lines. Scholars often refer to this hedging of bets to avoid litigation as “The California Effect” in a variety of industries, from software to car manufacturing.

Others who host files may cut off access to those particular states to avoid potential legal liability. Wilson told The Verge he’s preparing to “turn off” access to Defense Distributed’s gun files for users with IP addresses from affected states. Some printer manufacturers, particularly smaller players with less financial wiggle room, may simply exit those markets altogether.

“Our printers are made in the Czech Republic,” Hanson said. “They simply won’t sell in Washington if they have to jump through these hoops.”

Lawmakers pushing forward these mandatory gun-blocking software systems are hoping to get voluntary buy-in from the 3D printer industry.

During a ghost gun demo with reporters earlier this year, David Stuart, chief of the counterterrorism unit at the New York County District Attorney’s Office, told The Verge they have met regularly with printer manufacturers and file-hosting sites. Those meetings reportedly led several 3D printer manufacturers to update their user agreements and policies to prohibit firearm manufacturing. At least one file-hosting site also notified users that printing firearms is illegal and not in compliance with their policies following the DA’s outreach, Stuart said.

A past letter from the New York DA’s office addressed to printer maker Creality specifically named Print&Go’s 3D GUN’T software as a “common sense safeguard” it could potentially implement.

No 3D printer manufacturers or file-hosting sites would comment on whether they supported the firearm-blocking tech or how they intended to proceed in New York and California moving forward. Flashforge, Bambu Lab, Snapmaker, Prusa, Creality, MakerWorld, and Printables.com also did not respond to requests for comment.

In an emailed statement, Hugo Fromont, cofounder of the prominent 3D-printer file marketplace Cults said it already takes steps to remove models that violate the law and said that sharing firearm blueprints is “absolutely forbidden” under the company’s terms of service.

Concerns around this technology aren’t limited to accuracy and privacy. Makers told The Verge that well-meaning efforts to limit gun files open a Pandora’s box where other objects could be added to the no-print database over time. Once that infrastructure exists, they warn, corporate entities could lobby to expand it to protect their intellectual property. That strikes at the core of the right-to-repair movement.

Benjamin Heckendorn, an engineer and 3D printing enthusiast who’s spoken out against the new new bill on YouTube, described them as a kind of Trojan horse.

“I don’t even think these laws are about guns,” Heckendorn, who goes by the name Ben Heck Hacks, told The Verge in an email. “The real goal is stopping all the IP infringing stuff that people print.”

“If you think companies like John Deere, Disney, or Nintendo aren’t going to be interested in a world where your printer can automatically recognize and block objects that resemble their IP or their products you’re not paying attention to how aggressively big brands defend control when the tooling exists,” Loyal Moses speculated in a video criticizing AI file detection.

When The Verge asked whether Print&Go’s database could eventually be expanded beyond firearms, Amin didn’t entirely rule out the possibility.

“I cannot answer you because we are a company, so the decision is not something just in my hands,” he said.

Whether these anxieties around IP enforcement actually come to pass may depend less on gun blocking tech as a concept and more on the exact type of software process that’s implemented. A basic hashing approach, while easily bypassable, has much less inherent risk for abuse than a less proven file prediction approach.

Regardless of what anyone thinks about the merits of stemming the tide of guns, the blocking tech mandates under consideration would mark an inflection point in the trajectory of 3D printing as a whole. Printers, like so much else of the digital world, would now essentially require permission to work.

The question of whether to alter 3D printing’s path may then ultimately rest on how gravely one really views the threat of homemade, printed firearms. And in a country where the total number of firearms has been estimated to outnumber people, and where gun show loopholes and other trivial work arounds undermine even basic background check requirements, the threat of 3D-printed guns can feel premature.

Still, the uptick in high-profile violence involving printed firearms in recent years has awakened momentum for change. Even if the most ambitious forms of gun scanning tech are held at bay, it seems inevitably the earlier Wild West era of 3D printed firearms access is nearing its end.

3D printing: Sean Hollister

Art direction and additional 3D design: Cath Virginia