TIPPING POINT: The single-shot Liberator pistol is the first firearm that can be made entirely with plastic components forged with a 3D printer and computer-aided design (CAD) files downloaded from the internet.

Three-dimensional printers can already make guns, and may soon allow people to create gold, gems, food or drugs in their living rooms, the Customs Service has warned.

It suggests the law needs to be changed to control importing designs for restricted or prohibited goods in the same way as child pornography is restricted.

A report obtained under the Official Information Act says 3D printers have already been used for criminal activity and to create weapons. In Australia, one was used to make a working "card skimmer" device, which could steal credit card details

Designs exist online for printing working guns, such as the Liberator, created by Cody Wilson, a 26-year-old who calls himself a "crypto-anarchist".

The Customs report, Border Implications from Emerging Technologies, says 3D printers have passed a "tipping point" and will radically change how borders are policed. The ultimate end of the technology could allow molecular-level printing of "gold, gems, food or drugs".

The Customs and Excise Act is being reviewed, and Customs Minister Maurice Williamson, who requested the report after publicly voicing concern last year, said he could "almost guarantee" the review would include provisions to deal with 3D printing.

"How do you police a physical border when a vast amount of stuff could get past you by way of a digital file?" he said. "You may be able to carry through [customs] the digital specifications for it all . . . the printer can go ahead and produce [it]."

The technology had enormous potential but also significant risks, he said, and it was important to be ready to deal with what could be produced in years to come.

"You could be out of the back of a farm somewhere and break an 18-inch crescent wrench and just go over to the printer and print another one off. That's phenomenal. But not if your neighbour prints off a gun and pops over the fence and shoots you."

Current law might make it impossible to stop someone downloading and printing a gun, he said. The principle had not been tested in court. "It wouldn't breach any indecent publications legislation, there's nothing rude or crude about it."

Victoria University senior lecturer in industrial design Tim Miller, who has worked extensively with 3D printers, said Customs appeared to understand the potential of the technology and the issues it raised.

"I think the nature of the internet and the way material's freely available does pose incredible problems," he said. "I can't see any way other than legislation to make it illegal to import 3D files of a certain nature."

Customs proposes that importing such files could be covered by existing laws covering objectionable materials.

WHAT IS A 3-D PRINTER?

A 3-D printer is a machine that makes objects out of material from digital patterns. They are increasingly used by companies and individuals to make things ranging from synthetic body parts, tools and toothbrush handles to furniture.

For example, if you wanted to "print" a plastic fork, you would load up the printer with plastic and chose a fork design available on the internet. The printer then "prints" the fork by repeatedly laying thin layers of the plastic on top of each other according to the design.

This can be done with all kinds of different materials to produce an expanding range of objects on ever grander scales and at ever faster speeds.

So far, the most commercially successful use for the technology has been making customised hearing aids, according to Victoria University senior lecturer in industrial design Tim Miller.

Using a digital scan of the ear, earpieces can be printed to fit perfectly, he said.