California law targets firearm printing on some 3D printers, but exempts existing machines

California has enacted a law requiring firearm-prevention technology in certain 3D printers, but the requirement will not apply immediately to machines already sold or owned. Signed by Governor Gavin Newsom, the measure concerns future sales and transfers of covered printers in the state. It does not prohibit owning or ordinarily operating a machine without the eventual blocking capability.

The requirement depends on an applicable technical standard from ASTM International. The California Department of Justice must begin checking quarterly for such a standard no later than July 1, 2027, and continue through July 1, 2029. If no standard exists by then, the law’s required checks end. Until a benchmark is available, manufacturers lack the specification needed to implement the requirement.

Design detection presents technical challenges. One proposed approach compares digital files with databases of known firearm designs, but designs could be altered or split into printable parts. Another uses trained software to assess printed objects, but may misclassify legitimate components such as tubes, brackets, levers, or barrels.

California is the second US state, after New York, to establish restrictions specifically concerning firearm production with 3D-printing equipment. Colorado and Washington are pursuing comparable measures, but their proposals are not equivalent statewide requirements. The Electronic Frontier Foundation questioned the technology’s reliability. In June 2026, it said, “There is no world where the mandated technology actually works as intended.”