California AB 2047 Explained: What the New 3D Printer Gun Blocking Law Requires

The bill that started the year as a DOJ-certified detection mandate with criminal penalties was signed into law on September 26 as something much narrower: a conditional rule that only switches on if ASTM International writes a standard first. Here is what the law actually says, who it touches, and when anything could happen.

California’s AB 2047, the California Firearm Printing Prevention Act, passed both houses of the Legislature on August 31, 2026 and was signed by Governor Gavin Newsom on September 26, one of ten gun bills signed the same day. It takes effect on January 1, 2027. California becomes the second state, after New York, to tie the sale of 3D printers to the presence of firearm blocking technology, and the first to do so with no exemption for industrial machines.

That sentence needs an immediate qualifier, because most of what circulated about this bill in the spring no longer describes it. The version he signed has no criminal penalties, no fines, no manufacturer attestation, no public compliance list and no fixed date on which printers without blocking software become illegal to sell. What it has instead is a trigger: nothing is required of anyone until ASTM International publishes an industry standard for firearm blocking technology, and if that has not happened by July 1, 2029, the mandate may never activate at all.

Dates from the chaptered text of AB 2047, Civil Code section 3273.633, signed September 26, 2026.

What the bill requires, in plain language

AB 2047 adds a new Title 21.1 to the California Civil Code, starting at section 3273.631. The core obligation falls on manufacturers. Once the process below has run its course, a manufacturer may not sell, offer to sell or transfer for consideration a 3D printer to any person or business in California unless the printer is equipped with firearm blocking technology that meets minimum performance standards set by the California Department of Justice. A separate clause makes it unlawful to sell, offer for sale or transfer for consideration a non-compliant printer, wording broad enough to reach resellers rather than manufacturers alone.

The definition that matters is the one for the technology itself:

Three details in that definition are easy to miss. First, the check happens before every print job, on the file, not on the finished object. Second, the target is not only complete firearms but also machine gun conversion devices, the small parts that turn a semi-automatic weapon into an automatic one. Third, the bill does not say how the algorithm works. It leaves that entirely to the standards process described next.

The definition of a 3D printer is borrowed from existing law, Civil Code section 3273.60, which came in with AB 1089 in 2023. That definition covers additive manufacturing devices generally, and the final version of AB 2047 removed the earlier exemption for industrial machines. In practice that means an FDM desktop printer, a resin printer and a metal powder bed system sold into California would all be inside the scope. Two exemptions remain: printers used exclusively to make props for the entertainment industry, and people who distribute firearm manufacturing code solely to develop and test blocking technology.

The timeline, step by step

The mechanism is a chain of four conditions. Each one has to happen before the next can start.

Put the numbers together and the earliest realistic date for a sales restriction is 2028, and only if ASTM moved unusually fast and the DOJ used a fraction of its 24-month window. A standard published near the July 2029 cutoff would push enforcement to 2031 or 2032. And as the organizers of Formnext noted in September, California has no announced plan to commission ASTM to write such a standard, and ASTM standards are normally drafted with the participation of the very industry that opposed this bill.

How the bill changed between February and August

The bill was introduced by Assemblymember Rebecca Bauer-Kahan on February 17, 2026, with Everytown for Gun Safety as sponsor, and was amended five times before enrollment. The introduced version and the signed version are different laws.

The votes tell the same story of a bill that softened as it went. It cleared Assembly Public Safety 6 to 0 in March, Assembly Judiciary 9 to 3 in April, the Assembly floor 58 to 19 in May, Senate Public Safety 11 to 2 in June, Senate Judiciary 5 to 1 with amendments at the end of June, and the Senate floor 30 to 10 on August 31, with the Assembly concurring 60 to 18 the same day. The Senate Judiciary analysis records the author’s aim in one sentence: to require “that all three-dimensional printers sold in California are equipped with firearm blocking features to prohibit the printing of dangerous gun parts.”

The removal of the industrial exemption is the change that drew the least attention and may matter most. Trade coverage in August noted that makers of metal and polymer production systems had treated the bill as a consumer printer issue. Under the text as signed, it is not.

Who is affected, and who is not

Manufacturers selling into California carry the only obligation in the bill. That includes every brand in our best 3D printers guide and every industrial vendor, since the exemption is gone. How they comply is undefined until the DOJ rules exist.

People who already own a printer are not addressed. The bill regulates sale and transfer for consideration, not ownership or use, and the text as signed contains no user-side offense. The earlier misdemeanor for disabling the technology was removed. Whether the broad “unlawful to sell” clause could apply to a private second-hand sale years from now is a question the text does not answer and the DOJ’s regulations may.

Schools, libraries and makerspaces have no duties under the bill. Their exposure is indirect: if a sales rule ever takes effect, the printers they buy would need to comply, and campaigners argued during the spring that this would raise prices and narrow choice for the roughly 1.5 million California students who use 3D printing in class, a figure cited by the industry-side campaign rather than by the Legislature.

Open source firmware projects such as Klipper, Marlin and RepRap-derived designs were a central worry in the spring, when the bill included attestation and a user-side offense. The text as signed does not mention firmware, kits or self-built machines at all. That is not the same as an exemption; a self-assembled printer is still a printer under section 3273.60, and it would be for the DOJ to say how the rule applies to a machine with no manufacturer in the ordinary sense.

Does the technology exist?

Products exist. A Danish company, Create it REAL, announced a firearm component detection algorithm for printer firmware as far back as 2013, describing it as working like antivirus software against a central database of known gun files. Software company Print&Go launched a package called 3D GUN’T in late 2024 that combines file detection, print traceability and firmware protection, and has said openly that its ambition is for every printer user to have it installed. Both work in the way the law describes: the file is analyzed before the printer accepts the job.

Whether they work well enough to be mandated is the dispute. Detection has two routes. Matching against a database of known gun files is precise but trivially defeated by scaling, rotating, splitting or re-meshing a part. Recognizing firearm geometry with a trained model catches variants but produces false positives on anything that resembles a receiver, a barrel or a trigger group, which in a workshop includes a good many brackets, tubes and levers. Neither route reaches a printer running open firmware, an offline machine, or a print farm that has stripped the check out. The Electronic Frontier Foundation put the opposing case bluntly in June:

The Legislature’s answer to that argument is the ASTM trigger. Rather than assert that the technology works, the law as signed defers the question to a standards body and adds a feasibility test: the DOJ must find the published standard “technologically feasible” before it starts rulemaking. Critics read this as an admission; supporters read it as prudence. Either way, the burden of proving the technology has moved from Sacramento to whichever ASTM committee, if any, takes it up.

Who lined up on each side

Support, according to the Senate Judiciary Committee analysis, came from Everytown for Gun Safety as sponsor, Moms Demand Action, Newtown Action Alliance, the California chapter of the American College of Emergency Physicians, the CFT teachers’ union, the San Diego County School Board Association, Prosecutors Alliance Action and several Students Demand Action chapters. Law enforcement testimony cited in the Senate Public Safety analysis puts the increase in recovered 3D printed firearms at 1,000 percent between 2020 and 2024, and Everytown’s statement on passage cites a San Jose case in which 27 finished or nearly finished printed guns were found in an 18-year-old’s bedroom.

Opposition was an unusual coalition. The California Rifle and Pistol Association, the NRA and Gun Owners of California opposed it on Second Amendment grounds. MatterHackers, the Community Manufacturing Initiative and a group of aerospace and automation firms opposed it on feasibility and cost. The Electronic Frontier Foundation opposed it on speech and surveillance grounds. And a maker-community campaign run from the 3D Printing Nerd site, with signatories including Josef Prusa, Prusa Research, Printed Solid and Make: magazine, argued the bill would push printer makers to leave the California market rather than build detection into every machine. That campaign is where the “1.5 million students” and “$10.5 billion at risk” figures come from, and neither number appears in a legislative analysis.

New York got there first, with a different design

California is not alone. On May 28, 2026, Governor Kathy Hochul signed New York’s budget bill, which the governor’s office describes as a crackdown on 3D printed guns. New York’s law criminalizes distributing digital gun files, bans the sale of 3D printers without blocking technology to anyone who does not hold state and federal firearms licenses, and sets up a working group to report within a year on whether viable blocking technology exists. The printer sales ban only starts once that group says it does.

The two states have therefore landed in the same place by different routes. Both have a printer sales restriction on the books that is conditional on someone else certifying the technology first: a state working group in New York, ASTM International in California. For manufacturers the practical difference is timing. New York’s report is due around mid-2027; California’s clock does not start until July 2027 and can run to 2029 before anything is decided.

What the signing changes, and what to watch

The governor’s office issued no signing message specific to AB 2047; it went through in a package of ten firearms bills on September 26. The author framed it as a stop at the source.

Some early coverage of the signing has described the law as creating penalties for anyone who jailbreaks a printer. The text does not do that. The user-side offense was removed in the summer amendments, and the law as signed contains no penalty provision of its own; enforcement, if the sales rule ever activates, would have to come through the DOJ’s regulations or California’s general unfair competition law. The enforcement section of the 2023 law on firearm manufacturing machines, Civil Code section 3273.61, is untouched and continues to apply as before. Readers who see the “jailbreak penalty” claim repeated should check it against Civil Code section 3273.633.

Three things are worth watching from here. Whether ASTM’s additive manufacturing committee, F42, opens a work item on firearm blocking technology; without one, the California clock runs out in July 2029. What New York’s working group reports in 2027, because a finding either way will shape ASTM’s appetite. And how printer makers respond: whether any of them ships detection voluntarily, as Create it REAL has offered for more than a decade, or whether the industry’s position remains that intent cannot be read from geometry. For readers setting up a printer today, none of this changes anything; our 3D printing safety guide covers the risks that actually apply in a home workshop.