Software solutions for printers might block such usage (although I would think that is an easy hack).
Doubt it would be an easy hack to get rid of such blocks. Standard printers and scanners of recent manufacture have programming to allow them to recognize when someone is trying to scan or print currency and stop the operation. Or at the least put little micr stamps on the printout to let the feds track where it came from once they get their hands on the fake. You would think there would be a good demand for a printer that could print money for you. But so far, noone's hacked any. Granted, it's probably because it's easier to just get an older printer that doesn't have those protections.
Then again i doubt they could block a 3D printer from printing a gun. Blocking a printer from printing money is easy. All money looks the same, so you just need it to recognize one particular image and refuse to work with it.
There are however MANY different gun designs with MANY different parts in them, most of which would look exactly the same as any other mechanical part to a printer. It would be a huge undertaking to program them to recognize every part that could be used in a gun.
It would be like trying to regulate all "gun parts" sold in the country. Impossible since most gun parts can simply be sold as any number of things without anyone realizing.