Do you remember the Wiki Weapon project? It was a collection of individuals united a common banner - Defense Distributed - whose goal was to create the first fully 3D printed gun. They were inspired by the creation of a 3D printed lower receiver combined with metal parts that formed a fully working gun. They started an IndieGoGo project that was immediately shut down, but were still able to fund the initial lease of a Stratasys professional 3D printer.
Wired reports that Stratasys apparently didn't like what the guys at Defense Distributed were doing with their printer. Once they caught wind of the Wiki Weapon project, they immediately canceled the lease and reclaimed the printer. What was the problem? Stratasys claimed Defense Distributed was breaking the law by creating a 3D printed gun.
It's legal in the United States to make a gun in your backyard. Just like alcohol, however, you can not sell it without a license. Defense Distributed was on the right side of the law in this regard. Where they may have hit a snag is another law called the Undetectable Firearms Act which prevents the creation or sale of weapons that can not be detected by normal means. A plastic gun definitely falls into the category.
Going forward, Defense Distributed represents an important debate that needs to happen in regards to 3D printing. The technology that is 3D printing is all about the democratization of manufacturing. In a more romanticized universe, 3D printing would allow people to break from the supply and demand model by becoming their own manufacturer. Even if such a future is not particularly realistic, it still brings up the problem we're facing today. Should 3D printing, especially when it's being used to create items like guns, be regulated? Can you regulate it?
As of now, it looks like the companies that make 3D printers can regulate it. What happens when creators can make their own high-precision 3D printers? The Form 1 3D printer has already pulled in over $1 million on Kickstarter and shows no sign of stopping. It could easily be used to make weapon parts, and doesn't have an over protective company regulating how its products are used.
As for Defense Distributed, the group is now working with a legal team to procure a firearms manufacturing license. In all reality, this is the best way to go for now. The team first have to prove that making a complete gun with a 3D printer is even possible. They can start worrying about regulations after that.