Not long ago, it was the stuff of science fiction, but now US officials and lawmakers are grappling with a new reality -- citizens having the ability to print firearms at home.
A gun rights group blocked downloads of 3D gun plans from its website Tuesday after a federal judge sided with states arguing that the postings could help criminals and terrorists manufacture such weapons.
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While Judge Robert Lasnik's ruling didn't order the plans taken down, it temporarily blocked a settlement reached in June between Defense Distributed, a Texas-based gun rights organization, and the federal government that made it legal to post 3D printable gun plans online.
"This is a nationwide ban. ... It takes us back to a period of time before the federal government flipped on their policy regarding these 3D ghost guns," Washington Attorney General Bob Ferguson said.
So what's the controversy all about? Here some answers to your questions.
Just what are 3D-printed guns?
3D guns are firearms assembled from ABS plastic parts -- the same material found in Legos -- that can be made with a 3D printer. The Defense Distributed website would have allowed people to download plans for building a variety of 3D guns, including an AR-15-style rifle, a Beretta M9 handgun and other firearms.
How do you print a 3D gun?
3D printing uses computer-created digital models to create real-world objects, from simple chess pieces to more complex objects such as functioning clocks. The printers follow the shape of the model by stacking layer upon layer of plastic or other material to make the objects.
How hard is it to print one?
"Even machinists with average skills are able to produce 3D printed firearms," said Mitch Free, chairman & CEO of the 3D printing company ZYCI CNC Machining. He said 3D printing is more accessible than ever because of software improvements and some slight reductions in the cost of 3D scanners and fabrication tools.
Can anybody do it?
You'll need some money. The higher-end 3D printers needed to make such weapons cost thousands of dollars and may be too expensive for most people. Of course that doesn't ease the concerns of those who think guns made from 3D printers are a bad idea.
So why are some people against them?
Critics fear the DIY guns could create security concerns because they are untraceable and would largely be invisible to metal detectors. They also fear the technology makes it far too easy for terrorists and people who are too dangerous to pass criminal background checks to get their hands on guns.
What do defenders of these guns say?
Cody Wilson -- the founder of Defense Distributed and the person who introduced the world to 3D-printed guns -- and his supporters say the ability to build unregulated and untraceable guns will make it much harder, if not impossible, for governments to ban them. Wilson also sees this fight as a free speech issue. By suing the government for violating his First Amendment rights, he shifted the focus of the debate about 3D printed guns away from gun control to a discussion about access to data and information online.
Why did the US government intervene?
A few days after Defense Distributed posted its instructions for making a "Liberator" plastic gun in 2013, the US State Department sent a three-page cease-and-desist letter to Wilson demanding that the group remove them from its website. It accused Wilson of potentially breaching International Traffic in Arms Regulations, which regulate the export of defense materials, services and technical data. In essence, officials said, someone in another country that the United States doesn't sell weapons to could download the material and make guns.
What do lawmakers say about this?
In December 2013, a federal law requiring that all guns be detectable by metal screening machines was extended for another 10 years.
The law prohibits guns that don't contain enough metal to trigger screening machines commonly found in airports, courthouses and other secure areas accessible to the public.
Plastic gun designs got around this restriction by adding a removable metal block, which isn't required for the firearm to function.
In June, Sen. Bill Nelson, D-Florida, introduced a bill in the Senate that would amend the Undetectable Firearms Act to prohibit firearms that do not have a major component that can be detected at airport security screening.
How effective are the guns?
In 2013, the Bureau of Alcohol, Tobacco, Firearms and Explosives made public tests it has done on the Liberator model.
One gun made with a plastic called ABS-M30 fired a .380-caliber round without failing all eight times it was tested, ATF officials said, describing it as "a lethal weapon." Another pistol made from a plastic called VisiJet didn't perform as well, with video showing it exploding into a dozen plastic shards when fired.
Where does the case stand now?
The issue will go back to court on August 10, when both sides will argue over whether a preliminary injunction is needed.