The company behind the gun, Solid Concepts, has a federal license to make guns, so what they’ve done is not illegal. Rather, they argue in a blog post, they want to prove the efficacy of the approach they’ve taken. A firing test seems to prove them have.
What I find fascinating about 3D printers is the how they tie together a physical object with a digital description. More as we get into this chapter, but for now, just worth noting the milestone.