FALLS CHURCH, Va. (AP) — A federal appeals court on Monday revived a lawsuit challenging Maryland’s rules for obtaining a handgun as unconstitutionally restrictive.

The unanimous ruling from the 4th U.S. Circuit Court of Appeals in Richmond reinstates the lawsuit, which was first filed in 2016 and tossed out of court by a federal judge last year.

The lawsuit challenges Maryland’s handgun licensing law, passed in 2013, which requires gun purchasers to complete four hours of safety training in addition to passing background checks, being 21 years old and a Maryland resident.

The case was initially dismissed because the plaintiffs, including the advocacy group Maryland Shall Issue, lacked standing to sue.

But Monday’s ruling determined that one of the plaintiffs — Atlantic Guns, which operates shops in Rockville and Silver Spring — had standing to sue. The gun shop had argued that it lost business because of the rules and that its customers suffered under the licensing scheme.

The case now goes back to district court for a trial on the merits.

The opinion was written by Judge G. Steven Agee and joined by judges Julius Richardson and Barbara Milano Keenan. Agee and Richardson were appointed by Republican presidents, while Keenan was appointed by a Democrat.

Mark Pennak, president of Maryland Shall Issue, said he is pleased with the ruling and not at all surprised after witnessing oral arguments and seeing the appellate judges’ skepticism about the district court’s ruling.

He said the licensing requirements add hundreds of dollars in costs and significant amounts of time to acquire a license.

“It’s an astonishing burden,” he said.

Raquel Coombs, a spokeswoman for Maryland Attorney General Brian Frosh, a Democrat, said the ruling is under review and declined further comment Monday.

The requirement for training applies to handguns, not hunting rifles or shotguns.

The 2013 law that passed in the aftermath of the mass shooting at Sandy Hook Elementary School in Connecticut in December 2012 was one of the nation’s toughest. Other parts of the law, including a ban on certain types of rifles and high-capacity magazines, have faced separate challenges but have been upheld.