Committing a crime, such as possessing a 3D printed firearm?
Some folks have tried to reintroduce it again. It's one of the few gun laws that even the NRA approved of.
Not to mention: a magazine and all ammunition is automatically detectable (visually and magnetically.)
The federal laws do state that "possession of specific machine gun parts is considered possession of a machine gun"
Machine gun sears included. Also parts that convert a semi-automatic into a machine gun like a Lightening Link.
Unregistered machine guns are illegal to possess regardless of how they were made.
3D printing an otherwise legal firearm is not illegal at the Federal level in the United States.
The exchange boils down to:
Comment: That isn't illegal.
Reply: well, if you do this other thing that's illegal, it is.
That will be silly, counterproductive and even less impactful than having to show my license and sign an affidavit just to buy properly working cold meds in a gorram grocery store.