California already requires a license to 3d print firearms.[1] This is the same license needed to mass produce firearms, making legal individual manufacturing incredibly difficult. Also all firearms (even 3d printed ones) in California must have a metal serial number tag embedded in the frame. Given the number and manner of restrictions, I’m not aware of anyone in California who has legally printed a firearm since these laws came into effect.

https://leginfo.legislature.ca.gov/faces/billTextClient.xhtm...