Untraceable firearms, commonly known as ghost guns, will no longer be legal to sell under an executive order from President Joe Biden that takes effect Wednesday.

The weapons, which police say they are recovering with increasing frequency at crime scenes, were the subject of a Kane In Your Corner investigation in June.

Ghost guns were used in at least five school shootings this year alone, according to the Everytown Center for Gun Safety. Police say one was used in a shooting outside a high school in the Bronx in April, which left a 16-year-old girl dead.

Because ghost guns are manufactured without serial numbers, they are virtually untraceable by law enforcement. While they are already illegal to possess in New York, New Jersey and Connecticut, they can be legally purchased in 40 states, including Pennsylvania, often without a background check.

Under the Biden administration’s new regulations, all gun kits nationwide will have to carry serial numbers, like any other firearm. Existing ghost guns will not be impacted.

Brian Higgins, a former SWAT commander who now works as a law enforcement analyst with John Jay College of Criminal Justice, says he’s not completely convinced the new rules will succeed in keeping untraceable weapons out of the hands of criminals who are determined to have them. But he says something needed to be done.

“We have to stem the increase in violence, particularly shootings and homicides,” Higgins says. “And whether or not ghost guns really contribute to school shootings. I think we need to take every step, even if it's a reach, to try to address these mass shootings."

Gun rights groups have argued the regulations are not likely to succeed.

"As far as a criminal is concerned, it is far easier for them to steal a firearm and to obliterate the serial number than it is for them to manufacture a functioning firearm at home,” says Aidan Johnston of the Gun Owners of America.

But the gun lobby has so far not mounted much of a legal challenge to the executive order. Instead, Kane In Your Corner found some ghost gun sellers have been using the impending rules change as a sales pitch, with notes on their websites urging customers to purchase ghost gun kits before the new rules kick in.

“There's clearly a plan here,” Higgins says. “And it's very interesting that there were no preemptive legal challenges.” He predicts that legal challenges from the gun industry are likely still to come.

While the new rules will regulate the future sale of ghost guns, there’s no estimate on how many are already in circulation.