The Supreme Court justices gave a friendly hearing Tuesday to the Biden administration’s regulation that prohibits the sale of easy-to-assemble firearms that can be sold online or through the mail.

Tens of thousands of these so-called “ghost guns” have been found at crime scenes.

Because they have no serial numbers, police say they cannot trace them to a gun dealer who sold them or to the buyer.

Conservative judges in Texas had struck down the 2022 regulation, but the Supreme Court voted last year to keep it in effect pending the legal challenge.

During arguments Tuesday, the justices suggested they will uphold it as a reasonable interpretation of the 1968 law that restricts the sale of firearms.

Two years ago, “these ghost gun products were flooding the market. Our nation had seen an explosion of crimes because of these untraceable guns,” Solicitor Gen. Elizabeth Prelogar told the court.

She said the gun parts kits were appealing to criminals who could not obtain a gun legally and wanted a weapon that could not be traced back to them.

She argued the new federal regulation fit with the 1968 law and its definition of a firearm.

Gun-control advocates predicted the Supreme Court would uphold the ban.

“Today the ghost gun industry’s fiction that its gun building kits are not firearms crashed into a brick wall of reality in the Supreme Court,” said Eric Tirschwell, executive director of Everytown Law. “Every member of the high court seemed to recognize under Congress’ broad and flexible definition that a gun building kit which can quickly and easily be turned into an operable weapon is a firearm.”

The case of Garland vs. VanDerStok is not about the 2nd Amendment and the right to “keep and bear arms.” Rather, at issue is the legal definition of a firearm, as set in federal law.

The outcome could have a significant impact in California.

Los Angeles has had by far the largest number of “ghost guns” recovered from crime scenes, but the number declined by 28% last year, according to a friend-of-the-court brief filed by 20 major cities.

California has its own state law forbidding the sale of such gun kits, but state attorneys said the state ban would not be as effective if the federal regulation were voided.