Any tool can be used to make a weapon, 3D printing is no different. We don't have special legislation for CNC mills, sheet metal tools, carpentry, and the countless other machines (many have in their homes) that are used in weapons manufacture.

I think the main concern should be with the person making the illegal device and with the individuals providing files intended to facilitate that. I think Defense Distributed/Cody Wilson's action were fundamentally irresponsible: by providing files for a design that with the (intentional or accidental) exclusion of a single part creates an illegal firearm, Defense Distributed/Cody Wilson has failed to show some due diligence to indicate his intention was not to provide a means to produce illegal firearms. If he had made some effort to make it laborious for the “end user” to modify the design to be illegal, I might be more apt to tolerate his (BS IMO) flag waving, revolutionary manifesto.

If an individual uses these files and “forgets” to insert the metal plate making this unreliable, pointlessly expensive, single-shot, unrifled zip gun illegal, both the end user and Cody Wilson should be responsible for the creation and any actions that illegal device is used in.

More near term, I think external 3D printing companies should avoid the temptation to “lock-down” and instead continue to keep an eye out for files intended for illegal weapons manufacture. I think these companies should “CYA” and require users to “swear” before each order that no part is intended to be used in any illegal device. Also, governments (should and) are already starting to look at the current laws to see if/how they cover the distribution of blueprints for illegal or “nearly-illegal” devices.

In the very near term, I think it is very likely a few misguided folks will print these files on an FDM “noodle-extruder” (a machine quite different from an engineering grade Stratasys) and end up creating a handy combination facial scar creator/finger remover…. Darwin at his best.