...for now. I've yet to hear about a 3D printed gun that I would think was safe to be in the vicinity of when it was fired. Simple homemade zip guns are safer. I suppose a machined plastic composite (John Malcovich!) is effective & might slip through a metal detector (not sure how you get the ammo through) but we sure haven't heard much about them.
As the technology progresses this will likely change. But right now the high end 3D printer I have access to in my R&D lab couldn't create a decent, safe to use firearm. It could print out something that looks really cool & would freak people out!