It’s perfectly legal to manufacture your own firearm. However, it’s illegal to sell such a gun to anyone else without first obtaining a manufacturer’s license from the ATF. And since 1968, any gun that’s manufactured for sale must have a serial number. And since the plastic gun nonsense of ’80s (over those evil Glocks like the ones now carried by the FBI), it’s been illegal to manufacture and sell a gun that won’t set off a properly calibrated security metal detector. We’re talking serious felony time for breaking these laws
It doesn’t take much google-fu to learn those facts, but facts are inconvenient. They can get in the way of a good rant, one like the op-ed from the San Francisco Chronicle containing these lines:
Homemade firearms aren’t new, but a basement gunmaker generally isn’t allowed to sell such weapons. With unmarked, self-made plastic weapons, that limitation won’t exist at all.
As noted above, any unlicensed “manufacturer” commits a felony by selling any firearm regardless of how it was made.
No new laws further abridging the First and Second Amendments would be effective. The technology of 3D printing and the availability of inexpensive computer-controlled machine tools aren’t going to go away. The CAD files for many existing firearm designs are already in circulation on the Internet on servers beyond the reach of the American legal system. The battle has already been decided, and free speech and technical innovation have won.