California bill requiring 3D printers to block firearm printing becomes law

California Governor Gavin Newsom has signed a bill mandating 3D printer manufacturers to incorporate firearm-blocking technology into their products, following ASTM International's publication of a standard. This makes California the second state to enact such restrictions, following New York. Other states, including Colorado and Washington, also have similar bills pending in their legislatures.

The law affects only 3D printers yet to be sold, and existing printers do not require retrofitting. It does not ban non-compliant printers outright; it only regulates their sale and transfer, not ownership or use. Manufacturers will only need to implement firearm-blocking technology once ASTM International sets an industry standard.

The California Department of Justice is tasked with monitoring this process quarterly, starting from July 1, 2027, until July 1, 2029. If the organization fails to publish a standard within this period, the requirements for manufacturers would not be enforced. Detecting print files intended for 3D-printed firearms can be challenging, as two primary methods – matching against a known database or analyzing a trained model – have their limitations.

Both techniques could be easily bypassed or result in false positives, potentially preventing the printing of legitimate firearm components. The Electronic Frontier Foundation has expressed skepticism about the effectiveness of mandated technology, stating in June 2026 that "there is no world where the mandated technology actually works as intended."

To address these concerns, the California law requires the DOJ to base its implementation on standards set by ASTM International, rather than defining the technology itself. Existing 3D printers do not need to be retrofitted with the blocking feature, addressing one major concern of the 3D printing community.