Just as gun control has made a comeback among politicians after a spate of deadly mass shootings, the rapid advances in 3-D printed guns have threatened to undermine those controls before they even get started. According to a leading 3-D printing researcher, the only way to prevent printed guns from shooting a new loophole in the law may be to control the gunpowder you need to fire them.

"Perhaps the only way forward, if we choose to try and control this, is to control the gunpowder – the explosives – and not the actual device," Hod Lipson, a Cornell University professor of engineering and an early pioneer of 3-D printing, tells Danger Room. The reason, Lipson says, is that it would be the remaining "controlled substance" in a field that's otherwise uncontrollable, regardless of the shape or size of the firearm that you're using – or printing. It is the "unifying material everybody would need, and it would be a good target for regulation if people choose to regulate it."

This is because while gunpowder can be manufactured at home, it is largely unregulated for small arms ammunition. (Although making it in your basement can be difficult and dangerous.) Making usable bullet cartridges is relatively simple with gunpowder, brass and some machine tools. But making a 3-D printed gun is even easier, involving inexpensive printing machines which create everyday objects using layers of heated plastic, and structured according to blueprints that can be freely shared and downloaded.

Lipson doesn't make printed weapons. But for groups like Defense Distributed, a collective of 3-D printing gunsmiths which distributes firearms blueprints through its database Defcad, printable guns have been a means to directly challenge gun control legislation. Partially-printed guns have already been tested and refined by the group. In January, New York lawmakers banned magazines that hold more than seven rounds. In response, the group took to testing a printable 30-round magazine for the AR-15 rifle and named it the "Cuomo" after the state governor. The printable, plastic magazine survived after cycling through more than 300 rounds. Other hobbyists have since replicated Defense Distributed's design.

Preventing anyone from making a 3-D printed gun or magazine is also tricky, to say the least. A common target for gun control advocates is the "Gun Show Loophole," which allows gun sales between unlicensed individual buyers and sellers – without a background check – provided the sellers don't make a living off it. But for 3-D printed guns, the question over whether to conduct a background check doesn't even apply. The schematics are literally downloaded off the internet, shared anonymously, and serve as the blueprint for a gun anyone can make using plastic printer bought off a shelf. The guns themselves are not even sold to anyone, so how do you regulate it?

Lipson, who recently co-authored a book about 3-D printing, is cautious about what form gunpowder regulation could take, and didn't explicitly take a side for or against gun control. "Whether or not there should be gun control as an issue – I'm trying to avoid the question of whether or not there should be – if somebody is going to put in gun control, it's all about catching the one case," he says, referring to individual criminals. The problem, he adds, is that it's "very easy to make a one-off disposable plastic gun, if you like, that will shoot a few rounds. It's not something that will happen in 20 years. It is possible today to do that, and the technology is only getting better."

Note, however, these are not the kinds of firearms sold in gun stores, or the kind used by the military. They're relatively crude, require some metal parts to function, and cannot survive during long-term use. A lot can go wrong, namely that the thermoplastic used to print a gun can melt and fail during firing if it's brittle or absorbs too much heat.

Lipson should know: he's a pioneer in the 3-D printing field. As the director of Cornell's Creative Machine Labs, he's led development in the Fab@Home Project, an open-source collective that created one of first 3-D printers that can use multiple materials – and that has reached the public. Lipson's printers have since been used to print everything from artificial limbs to edible food.

Lipson also doesn't believe criminals or those who would use the guns for sinister reasons would print one instead of simply buying a cheap conventional handgun. But even a working pistol that will fire enough rounds to kill someone could be enough to break gun control at the sale point – skipping around rigorous background checks and restrictions on high-capacity magazines.

"Criminals have other channels to get guns, but I am really more concerned about hobbyists and enthusiastic kids trying this route at home and actually injuring themselves in the process of doing that," Lipson says. "If you make one and got it in the wrong temperature or was shoddy in any way, it's actually dangerous to fire."

This is a problem for Defense Distributed. The group has been cautious to note that "melting and failing in your hand will be a concern," according to the group's website. Hence the need for a lot of testing.

But there's a dilemma inherent to the group's vision of open-source weapons. It's a question whether freely shared blueprints, modified with anonymity – and with zero oversight and regulation – can be truly made safe for the user. Sharing faulty blueprints could also make for a dangerous kind of trolling. That's all a moot point if the guns don't have the powder to shoot.