WASHINGTON -- Federal officials have determined that a 3D gun printed from blueprints available online qualifies as a deadly weapon and worry it could evade metal detectors at courthouses, schools and other public places. 
 
 The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) produced its own version of the Liberator, a gun made of plastic that can be produced using a 3D printer and blueprints made available online earlier this year. 
 
 "We downloaded files, we created firearms from those files, and we tested those firearms," Earl Griffith, chief of ATF's firearms technology branch, said in a briefing with reporters at ATF headquarters in Washington Wednesday. 
 
 The design of the Liberator includes a block of metal that technically makes it legal under the Undetectable Firearms Act, which requires that a certain amount of metal be included in a weapon so it is detectable. But the metal plays no role in the weapon's function and could be easily removed. 
 
 The ATF's testing showed that the weapon, while not quite as powerful as most guns, could penetrate several inches of soft flesh as well as a human skull. The Liberator can only fire one shot before it must be reloaded, but ATF officials said that's all a determined assassin needs. 
 
 "The bottom line is, the penetration results demonstrated that the Liberator is a lethal weapon," Griffith said. "The .380 bullets fired from the Liberator penetrate sufficiently to reach vital organs and perforate the skull." 
 
 Testing found that the type of material used in the 3D printing was critical to whether the weapon would function properly. The ATF produced several versions of the weapon, some using plastic produced by the company Visijet and others using acrylonitrile butadiene styrene (ABS) plastic material. The Visijet version actually exploded during the test, as seen in the video above. 
 
 Griffith said that while the Liberator is the only 3D weapon available on a wide basis, ATF officials fully expect to see other models in the future. The ATF created its own 3D weapon that fired shotgun shells, and Griffith said he believed ABS material could be used to create an automatic weapon down the line. 
 
 "It is something that we've never seen before," said Richard Marianos, an assistant director at ATF. "It can defeat metal detection, and that's something we're concerned about." 
 
 The ATF has worked with officials from the TSA, the Secret Service and the FBI, all of which are concerned about the spread of 3D weapons. They aren't so concerned about the weapons becoming common on the street, but are more worried about people using 3D weapons to evade typical detection and get into areas where weapons would normally be banned. Agency officials declined to say whether the ATF actually owns its own 3D printer, which can cost anywhere from a few thousand dollars to hundreds of thousands of dollars. 
 
 When Congress passed the Undetectable Firearms Act in 1988 and renewed it in 2003, plastic guns "were only a theory," said Griffith. "Now, it's reality, because we do have the Liberator-type firearm." The law is set to expire in December, meaning it would be legal to possess a Liberator without the metal block that now brings it into compliance with the law. 
 
 Currently, X-ray machines used in many federal facilities can detect 3D weapons, unless they are broken down into component parts, in which case it may be up to security officials to recognize the individual components of the weapon. "Not every place you go to is like the airport," Griffith said. "A lot of places, [like] courthouses, all they have are metal detectors." ||||| (CNN) A federal judge Tuesday night ruled it is illegal to post blueprints for 3D-printable guns online, but hundreds of designs reportedly were downloaded before the judge's decision, meaning those designs are out there -- legally or not. 
 
 Judge Robert Lasnik, siding with states that argued the postings could help criminals and terrorists manufacture such weapons, temporarily blocked a settlement that would have allowed Defense Distributed, a Texas-based gun rights organization, to legally post blueprints for 3D-printable guns. 
 
 "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 state Attorney General Bob Ferguson said on "Anderson Cooper 360˚". 
 
 "What it means is if anyone posts this information online, they are in violation of federal law and can suffer very serious consequences. So, it makes it unlawful to post that information and make it available to the public." 
 
 The issue will go back to court on August 10, when the sides will discuss whether a preliminary injunction is needed. 
 
 Defense Distributed founder Cody Wilson said he has effectively shut down his site for now as a result of Lasnik's decision. 
 
 "By order of a federal judge in the Western District of Washington, http://DEFCAD.com is going dark," he tweeted. 
 
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 Tuesday's decision is the latest chapter is a yearslong struggle between Defense United and gun control advocates who argue that such weapons would be without serial numbers and therefore untraceable, that they could be in some cases undetectable by metal detectors, and that they would enable more people to get guns without submitting to background checks. 
 
 Another organization, the Firearms Policy Coalition, posted the plans online, saying it "does not recognize" the court order. 
 
 Spokesman Craig DeLuz said the group in Sacramento, California, downloaded the information from Defense Distributed when the site was operating. He said others have made the information available online, as well. 
 
 How we got here 
 
 Wilson had been in a multiyear legal battle with the federal government since 2013, when he posted designs in 2013 for a 3D-printed handgun he called the Liberator. 
 
 The single-shot pistol was made almost entirely out of ABS plastic -- the same material Lego blocks are made from -- and could be made on a 3D printer. The files also included plans for a tabletop, computer numerical control milling machine that could carve, rather than print, other gun parts out of aluminum, according to court documents. 
 
 In 2013, the US government made Defense Distributed take the blueprints down, saying they would violate International Traffic in Arms Regulations, potentially allowing someone in a country to which the United States doesn't sell weapons to download the plans to make their own guns. Wilson sued the federal government in 2015, and the Trump administration settled the case in June. 
 
 But Washington and other states asked Lasnik to halt the settlement -- and Lasnik found the government didn't follow procedure when agreeing to it. 
 
 "Plaintiffs have shown a likelihood of success on the merits of their Administrative Procedure Act claim," the judge wrote. 
 
 CNN reached out to Josh Blackman, an attorney for Defense Distributed, for comment. 
 
 Ferguson announced Monday he was leading the lawsuit , which originally involved eight states and the District of Columbia. The petition for the temporary restraining order was filed in federal court in Seattle. Iowa and Virginia joined the case on Tuesday. 
 
 The Liberator, Wilson's plastic pistol, would contain a 6-ounce piece of steel that can be removed, raising the possibility that walk-through metal detectors would not detect the guns, Ferguson and other states' attorneys general alleged in the lawsuit before Lasnik. 
 
 Gun control advocates have warned that such weapons would be made without serial numbers and be largely untraceable by law enforcement. Proliferation of 3D printing plans also would make it easier for people who cannot pass criminal background checks to access guns, they say. 
 
 But Alan Gottlieb, a founder and vice president of the Second Amendment Foundation, told CNN's "Cuomo Prime Time" that it was a matter of applying the First Amendment to protect citizens' Second Amendment rights. He said some communities are losing access to firearms sellers because of local laws. 
 
 "If you're allowed to own a firearm in your own home," he said, "you should be able to make the firearm in your own home if you can't buy one locally because of crazy restrictions." 
 
 What it takes to make 3D printed guns 
 
 The high-end 3D printers needed to make such weapons cost thousands of dollars. Mitch Free, chairman and CEO of the ZYCI manufacturing company in Atlanta, says he believes such a printer would cost $3,000 to $5,000, and the plastic needed to print a gun would cost around $50. 
 
 Hobby versions of computer numerical control milling machines, meanwhile, could cost around $2,000, said Free, whose company manufacturers a variety of products with 3D printing and CNC machining. 
 
 But someone also could access these printers and CNC milling machines through a monthly membership -- perhaps $100 or more -- at a makers' collective that already owns them, Free said. 
 
 Free said people wanting to use these methods to make a gun generally would need a mechanical background with decent technology skills. 
 
 "It's not plug-and-play," he said. Still, "if you're curious and somewhat intelligent, you'll figure it out." 
 
 New York: Release of plans is 'reckless' 
 
 New York Gov. Andrew Cuomo also announced a series of actions Tuesday to prevent the distribution of the 3D-printable gun designs. Cuomo issued a cease-and-desist letter to Defense Distributed to block the distribution of designs for 3D-printed guns in New York. The governor called the impending release "reckless." 
 
 Cuomo directed state police to issue a notice reminding New Yorkers that manufacturing firearms defined as assault weapons is illegal in New York. 
 
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 "As the nation rises up and calls for action against gun violence, it is absurd and frightening that the federal government wants to make accessing an automatic weapon as easy as hitting print," he said. "New York is proud to have the strongest gun safety laws in the nation, and we won't let this federal government take us backwards." 
 
 Cuomo said he will pursue legislation to bolster the state's gun safety laws and outlaw private production of all 3D-printed and "ghost guns" that are untraceable and invisible to metal detectors. 
 
 Cuomo's actions came after Pennsylvania went to court Sunday to block early distribution of the plans, which weren't supposed to be available for download until Wednesday. But more than 1,000 designs were downloaded recently in advance of the agreed-upon August 1 date. 
 
 At the hearing, Defense Distributed agreed to block Pennsylvania IP addresses for a few days until a more formal hearing could be held. 
 
 Blackman, the Defense Distributed lawyer, told CNN on Monday the Pennsylvania case was about free speech rights, not the manufacture of guns. 
 
 "One state cannot censor the speech of a citizen in another state," he said. 
 
 'We know this fight is not yet over' 
 
 The National Rifle Association said Tuesday that undetectable guns already are illegal. 
 
 "Many antigun politicians and members of the media have wrongly claimed that 3D-printing technology will allow for the production and widespread proliferation of undetectable plastic firearms," said Chris Cox, the NRA's executive director for legislative action. 
 
 "Regardless of what a person may be able to publish on the internet, undetectable plastic guns have been illegal for 30 years. Federal law passed in 1988, crafted with the NRA's support, makes it unlawful to manufacture, import, sell, ship, deliver, possess, transfer or receive an undetectable firearm." 
 
 The statement came after President Donald Trump expressed skepticism over the ability to download plans for 3D-printed guns legally, saying in a tweet that he's spoken with the NRA about them because the technology "doesn't seem to make much sense!" 
 
 The Brady Campaign to Prevent Gun Violence applauded the decision temporarily blocking the 3D-printed guns. 
 
 "It is immediately obvious to anyone who looks at this issue that 3D-printed guns are nothing short of a menace to society, and we are thrilled that the court ruled in this manner," Avery Gardiner, co-president of the Brady Campaign, said in a statement. 
 
 "The efforts of these attorneys general throughout the nation have helped strike a powerful blow against the scourge of 3D-printed guns, but we know this fight is not yet over. We will continue to do everything in our power to make sure that this temporary halt in publication becomes a permanent one."
– After months of creating plastic guns with 3D printers, ATF agents have confirmed that they work—a lot of the time—and can be both lethal and very hard to detect. "We downloaded files, we created firearms from those files, and we tested those firearms," said the chief of the agency's firearms technology branch after experiments with the Liberator, a plastic handgun that can be printed with blueprints posted online that were downloaded more than 100,000 times earlier this year. To comply with the soon-to-expire Undetectable Firearms Act, the Liberator design includes a few ounces of metal, but it can be removed and the weapon works perfectly without it, the Huffington Post reports. The agency also created its own 3D-printed weapon that fires shotgun shells, and it believes automatic weapons are also possible. Officials don't think many criminals plan to ditch metal guns for the printable kind, but they fear an assassin could easily smuggle one into a secure area. The weapons "create a public-safety concern ... whether we appear in court, whether we get on an airplane, whether we go to a concert—any type of venue, it presents a challenge for law enforcement," an ATF official tells the Wall Street Journal.