Debate over this is stupid to me because intrinsic to the debate is the premise that a segment of our population isn't protected under the 2nd amendment. You're either a threat to society and shouldn't be in it, or you're not and should be part of society with all the rights inherent therein.
That philosophical point aside, the laws preventing people from getting a firearm transferred to them through "normal" channels also prevent them from legally possessing them. If someone prohibited from obtaining a firearm wants one despite the law, they could either machine a gun(it's not hard...as once famously declared, your average technical tom could make a gun from loose parts in their garage, or from filipino curtain rods), steal a gun, or use someone to straw purchase them a gun. They're already breaking the law by possessing it, but they'd stop because of respect for transfer laws?
If I have a cnc machine at home, how is "3d printing" very different from programming the cnc to make me a lower like I could now(assuming I had space and lots of money)? I also wonder if the people upset about this would be cool with me 3d printing a spear, knife, or club?
Don't worry. When I am elected prez I will re-privatize medicine and socialize the gun industry. Owning a gun is a human right. They will be passed out in the projects like Obama phones are now.