The Supreme Court on Monday allowed the Biden administration to continue regulating so-called ghost guns – untraceable homemade weapons – as firearms under federal law.

The court’s brief order grants the Justice Department’s request to wipe away a lower court order and allow the regulations to remain in effect while a legal challenge brought by firearm manufacturers continues to play out in the lower courts.

There were no noted dissents to the order.

Ghost guns are kits that a user can buy online to assemble a fully functional firearm. They have no serial numbers, do not require background checks and provide no transfer records for easy traceability. Critics say they are attractive to people who are legally prohibited from buying firearms.

In the Justice Department’s emergency application to the justices, Solicitor General Elizabeth Prelogar pointed out that a district court judge had essentially ignored an order the Supreme Court issued just two months ago.

Back in August, a 5-4 court sided with the Biden administration in a challenge brought by a group of manufacturers and allowed the regulations to remain in effect while legal challenges play out. At the time, Chief Justice John Roberts and Justice Amy Coney Barrett sided with the liberal justices in the government’s favor.

After the order was issued, however, a district court judge based in Texas stepped in to block the regulations as applied to two manufacturers. The injunction was then largely upheld by the conservative 5th US Circuit Court of Appeals.

In an unusually sharp filing, Prelogar told the justices in an emergency application that the district court and the 5th Circuit “have effectively countermanded this Court’s authoritative determination about the status quo that should prevail during appellate proceedings in this case.”

The court “should not tolerate that affront,” she wrote.

“Although there’s no explanation for today’s ruling, it’s hard to see it as anything other than a repudiation of the lower courts for not correctly reading the tea leaves of the court’s August ruling that froze a similar injunction,” said Steve Vladeck, CNN Supreme Court analyst and professor at the University of Texas School of Law. “In that sense, it’s just the latest in an increasing line of rulings by the Supreme Court pushing back against district courts in Texas and the 5th Circuit.”

Prelogar called the lower court ruling “a grave threat to public safety because the lack of background checks makes ghost guns uniquely appealing to felons, minors, and other prohibited persons – and because when ghost guns are inevitably used in crime, they are essentially impossible to trace.”

In 2022, the Bureau of Alcohol, Tobacco, Firearms and Explosives updated its regulations to define the kits as firearms under the law so that the government could more carefully track them.

The rule does not prohibit the sale or possession of any ghost gun kit, nor does it block an individual from purchasing such a kit. Instead, it requires compliance with federal laws that impose conditions on the commercial sale of firearms. Those conditions include requirements that commercial manufacturers and sellers mark products with serial numbers and keep records to allow law enforcement to trace firearms used in crimes.