It's also already illegal to manufacture weapons without the required licenses, so if someone is okay breaking that law, they would probably be okay making their own 3D printer or CNC machine from the commodity parts they are made from.
What next, ban aluminium profile and stepper motors? Let's not forget hex head screws! I hear CNC machines have a lot of wiring, maybe they will ban the element copper.
All that to say, this would be both ineffective at changing the problem and extremely frustrating to law abiding citizens. Stifling innovation is one thing, squashing small businesses regular operations would be another outcome. CNC machines have been around for decades, powering small industries that have pumping out bespoke parts for years.
To me this is all fearmongering to try and restrict people from making their own stuff instead of buying it all or fixing old stuff.
This is an overreaction by some, and a chance to exploit by others.