California bill requiring 3D printers to block firearm printing becomes law — existing machines are exempt, but mandate hinges on unwritten ASTM standard

California Gov. Gavin Newsom has signed into law a bill that requires 3D printer manufacturers to include firearm-blocking technology in their products once an industry standard is published by ASTM International. This makes California the second state to enact firearm restrictions on 3D printers following New York. Two other states, Colorado and Washington state, also have similar bills that would require “blocking features” moving through state legislatures.

Since the law only affects 3D printers that have yet to be sold, existing 3D printers do not need to be retrofitted with firearm-blocking technology, addressing one of the major concerns of the 3D printing community. It’s also not a straightforward ban on non-compliant printers and only regulates the sale and transfer of 3D printers, not their ownership or use.

The application of firearm-blocking technology on 3D printers will only be required for manufacturers once ASTM International, a non-profit organization that sets voluntary standards across different industries, publishes or adopts a standard for firearm-blocking technology for 3D printers. The law mandates the California Department of Justice (DOJ) to check for a standard quarterly, starting no later than July 1, 2027, until July 1, 2029. If the organization hasn’t published a standard by that date, then the DOJ is no longer required to check for it, meaning the process to write the guidelines or regulations that manufacturers need to follow to sell 3D printers in California might not even begin.

There are currently two primary ways to detect if a print file is intended for a 3D-printed firearm — it could either be matched against a known database of gun files or analyzed by a trained model to determine if the design could potentially be used for a firearm. However, both techniques suffer from shortcomings. The former could easily be defeated by just modifying the file, like changing its size or splitting it into multiple pieces for later assembly, while the latter is prone to false positives and could prevent the printing of barrels, brackets, levers, tubes, and other parts that may look similar but have a totally different, legitimate use. This is one of the reasons why the Electronic Frontier Foundation said in June 2026 that “there is no world where the mandated technology actually works as intended.”

The California law attempts to address these concerns raised by 3D printing enthusiasts by mandating the DOJ to base its implementation on standards set by ASTM International instead of defining it itself. So, until the standards group publishes or adopts one within the set timeframe, the requirements for manufacturers to build the technology into their 3D printer models would not come into play.

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