EXCLUSIVE: A new Department of Homeland Security intelligence bulletin warns it could be "impossible" to stop 3D-printed guns from being made, not to mention getting past security checkpoints.

A May 21 bulletin distributed to numerous state and federal law enforcement agencies and obtained by FoxNews.com states that the guns, which can be made by downloading blueprints into cutting edge computers that mold three-dimensional items from melted plastic, "poses public safety risks" and are likely beyond the current reach of regulators. The guns threaten to render 3D gun control efforts useless if their manufacture becomes more widespread.

"Significant advances in three-dimensional (3D) printing capabilities, availability of free digital 3D printer files for firearms components, and difficulty regulating file sharing may present public safety risks from unqualified gun seekers who obtain or manufacture 3D printed guns," warns the bulletin compiled by the Joint Regional Intelligence Center.

[pullquote]

The bulletin refers specifically to Defense Distributed, a nonprofit company started by a University of Texas law student, which has successfully made and fired a 3D gun whose only metal parts are the bullets and a small firing pin. Some 100,000 plans for a gun called "The Liberator" were downloaded in just a few days before May 3, when a branch of the U.S. State Department told it to stop sharing the file. But the government bulletin seems to acknowledge that the genie is out of the bottle.

"Limiting access may be impossible," concludes the three-page bulletin.

A source tells FoxNews.com the potential problems faced by government authorities involve securing large, high-profile events or those attended by the President, where magnetometers used to screen for weapons would not pick up a 3D printed gun.

"This is a serious threat," the law enforcement source said. "These could defeat magnetometers. The only security procedure to catch [the 3D firearms] is a pat down. Is America ready for pat-downs at every event?"

In a section called "Liberator design poses Public Safety Risks," the bulletin explains:

"Magnetometers may fail to detect the Liberator, depending on device sensitivity. Though it is prohibited by federal law, manufacturers may deliberately omit the unnecessary metal insert, leaving only a small nail and ammunition as the sole metal component. Future designs could further reduce or eliminate metal entirely.

"Unqualified gun seekers may be able to acquire or manufacture their own Liberators with no background checks."

Other concerns mentioned in the bulletin include: that 3D-printed firearms can be made without serial numbers or unique identifiers, hindering ballistics testing. And improvements in technology and decreasing 3D printer costs are likely to mean even more sophisticated printed guns will become easier to acquire.

"Proposed legislation to ban 3D printing of weapons may deter, but cannot completely prevent their production," the memo says. "Even if the practice is prohibited by new legislation, online distribution of these digital files will be as difficult to control as any other illegally traded music, movie or software files."