A measure signed by Governor J.B. Pritzker on Wednesday morning outlaws unmarked “ghost guns” and makes Illinois the only state in the Midwest to ban such weapons.

President Joe Biden and the U.S. Justice Department last month announced new regulations on ghost guns, which can be assembled within minutes and bear no serial numbers, making them largely untraceable.

The Illinois law requires all firearms, including 3D-printed guns, to be marked with serial numbers.

“A child should not be able to build an AR-15 like they’re building a toy truck. A convicted domestic abuser should not be able to evade scrutiny by using a 3D printer to make a gun,” Pritzker said at the bill signing in St. Sabina Church’s gymnasium, surrounded by Mayor Lori Lightfoot, Chicago Police Superintendent David Brown, and community leaders.

“This law will ban those ghost guns and others, and will help keep families and communities safe,” the governor said.

Under the law, people who own gun kits would have to get them stamped with serial numbers within 180 days of the effective date of the law. Anyone with a firearm or gun kit without a serial number would be guilty of a Class A misdemeanor for a first violation. A second violation would be a Class 3 felony.

Pritzker said more than 20,000 ghost guns were involved in criminal investigations nationwide last year, a 10-fold increase from 2016.

Earlier this month, law enforcement seized a self-manufactured gun from a teenager at Oak Park River Forest High School. A teenage boy arrested during weekend violence in downtown Chicago was carrying a ghost gun, according to Chicago police.

Illinois State Police say ghost guns have been recovered during arrests for armed carjackings.

“This is a crisis moment for us around violence in general, but also around the proliferation of these ghost guns,” Lightfoot said. “Folks, we gotta wake up. The gun manufacturers are getting rich while we are burying boys and girls and elders all over this country without any consequences for the people who are part and parcel of the problem. And that’s also the gun manufacturers.”

Illinois State Police Director Brendan Kelly said his agency analyzed 63 ghost guns in 2020. That number increased to 180 cases in 2021. This year, the agency already has 164 ghosts in its laboratory system, he said.

“We’re going to double it every year at this rate,” Kelly said. “Criminals are finding it easier and cheaper to buy an unfinished firearm frame than to steal a gun or find one on the streets where the serial number has been fixed.

“With a little work, the unfinished frame becomes a fully functioning firearm,” he said. “We’re talking about both pistols and AR-15s. And it’s not just the guns. We’re finding extended magazines and high-capacity-round magazines.”

Illinois Republican lawmakers in both chambers voted against the measure or didn’t vote at all, some over constitutional concerns.

Pritzker criticized Republicans for their lack of support. “Why isn’t this a bipartisan bill? Because now it’s an election year,” the governor said. “So the NRA gun lobby has told Republicans they can’t vote for a bill like that. So they didn’t.”

The NRA’s Institute for Legislative Action had written its supporters to contact Pritzker’s office and urge a veto, contending the measure “only harasses and inconveniences law-abiding hobbyists who like to build their own firearms.”

“It is already illegal under state and federal law for prohibited persons, such as felons, to possess any firearms, whether commercially made or home built,” the NRA said.

Under a new Justice Department rule, ghost guns are treated like other firearms made and sold in the United States. Sellers must be federally licensed, run background checks before selling a homemade gun kit and keep records of the purchases.