This would be a stupid and utterly inconsequential law based on fear mongering. There are already laws against unlicensed gun smithery, and already laws against

This would be a stupid and utterly inconsequential law based on fear mongering. There are already laws against unlicensed gun smithery, and already laws against completely polymer or ceramic guns, there's no need to add more. Additionally, if someone wants to make an improvised firearm they can just go to home depot, spend less than $100 and build something that is far more capable than what can be produced from a multi-thousand dollar 3D printer.