3D printers have absolutely no clue about what it is that they are printing. They just receive X, Y and Z coordinates, temperature settings and extruder feed rates.
Just like an injection molding machine doesn't care about what the shape of the mold is. Just like a lathe doesn't have any restrictions on what you can make as long as it fits the chuck and the tooling.
I'm completely against regulation of any sorts on 3D printing, but you have to admit there is a huge difference in purpose there.