Only one problem for the anti-rights crowd: unlike printers and scanners where the government successfully prevailed on them to include intelligence to prevent use in counterfeiting, 3D printers are a popular DIY item. Not just USING them, but BUILDING them from scratch. Tough to regulate the functionality of stuff people build on their own. In fact one printer design is actually named for the fact that it can print the critical parts to spawn one just like itself.