Well, that was predictable: days after a 3D printed gun fired a few rounds, Rep Steve Israel has called for a ban on of Wiki Weapons. The congressman points out (correctly) that all-plastic 3D printed weapons would not be easy to spot using traditional methods, such as metal detectors.
However, what Rep Israel doesn't say is how he hopes to accomplish his goal. Firmware locks for 3D printers? A DMCA-like takedown regime for 3D shapefiles that can be used to generate plastic firearms (or parts of plastic firearms?). A mandate on 3D printer manufacturers to somehow magically make it impossible for their products to print out gun-parts?
Every one of those measures is a nonsense and worse: unworkable combinations of authoritarianism, censorship, and wishful thinking. Importantly, none of these would prevent people from manufacturing plastic guns. And all of these measures would grossly interfere with the lawful operation of 3D printers.