For the last half decade, 3-D printed pistols and metal-milled "ghost guns" have only rarely caught the attention of lawmakers, and have barely registered in the mainstream of America's gun control debate. But now, a controversial legal settlement may have unlocked a new era of digitally fabricated, DIY guns. It's also unleashed a political backlash unlike anything seen in the five years since the first 3-D printable firearm appeared online.

Earlier this month, WIRED broke the news that gun access group Defense Distributed had obtained a key settlement in its lawsuit against the State Department, winning the right to publish the blueprints and CAD models for practically any commercially available gun, files ready to be downloaded from the web and fed into a 3-D printer or computer-controlled milling machine to produce a lethal weapon in the unregulated privacy of anyone's garage.

In the weeks since, the reaction has snowballed: A growing coalition of state attorneys general have launched a belated effort to undo the agreement, and two lawmakers have introduced a bill that would make it far harder to legally produce or own a 3-D printed plastic gun. Even President Donald Trump tweeted about the issue Tuesday morning, in what vaguely sounded like opposition to public availability of 3-D printed guns.

On Monday, attorneys general from 20 states announced that they're suing the US State Department and Defense Distributed, in an effort to force them to rescind their settlement. The AGs are asking for an immediate restraining order to prevent the gun group from publishing its digital firearm files. Their central claim: The State Department violated the Tenth Amendment's constitutional protection of states' rights to make their own laws—including those governing gun control.

"We’re going to court to say this violates our state laws that are there to protect public safety," says Maura Healey, the attorney general of Massachusetts. "It puts our residents at risk of harm. It puts weapons into the hands of people who otherwise wouldn’t be able to acquire them."

On top of that state law claim, the AGs also argue the State Department's settlement violated the Administrative Procedure Act. That law governs the process by which regulatory bodies change their rules, and requires a period of public comment—and consideration of those comments—before an agency makes a regulatory change. The attorneys general argue that in its unexplained, sudden settlement with Defense Distributed, the State Department changed the rules around an individual's freedom to post digital gun files online without considering public comments, and thus broke the law. "There has to be a certain process and transparency, there has to be an explanation for the change, and all of that’s completely lacking here," says Healey.