Maryland Attorney General Brian E. Frosh helped pass the state’s assault weapons ban as a member of the state senate. (Jonathan Newton/The Washington Post)

A federal appeals court on Thursday cast doubt on the legality of Maryland’s 2013 ban on semiautomatic high-capacity assault weapons that passed after the mass shootings at a Newtown, Conn., elementary school.

The 2-to-1 decision by a panel of the U.S. Court of Appeals for the 4th Circuit sends the gun-control law back to a lower court for review, but allows the existing ban to remain in place.

Chief Judge William B. Traxler Jr., writing for the majority, found that the Maryland law “significantly burdens the exercise of the right to arm oneself at home” and should have been analyzed using a more stringent legal standard.

The law bans more than 45 types of assault weapons in addition to high-capacity magazines that hold more than 10 rounds of ammunition. Proponents said such weapons are disproportionately used in acts of mass violence and rarely for self-defense.

A federal law banning assault weapons expired in 2004, but six other states, including California, Massachusetts and New York, have similar bans.

The Maryland law was challenged by a group of gun-store owners and individuals who said the prohibited firearms are not military weapons and are used for lawful purposes such as self-defense, target practice and hunting.

Maryland Attorney General Brian E. Frosh (D), who helped pass the law as a state senator, said Thursday that the court majority got it wrong.

“I think it’s just common sense that the Second Amendment does not give people a right to own military-style assault weapons,” he said.

In a strongly worded dissent, Judge Robert B. King wrote: “Let’s be real: The assault weapons banned by Maryland’s [law] are exceptionally lethal weapons of war” and as such, he said, not necessarily protected by the Second Amendment.

King, a Bill Clinton appointee, noted that the panel’s ruling is at odds with several other federal appellate courts that have considered similar bans, including the D.C. Circuit. In 2011, the D.C. Circuit upheld the city’s prohibition on assault weapons and high-capacity magazines.

“To put it mildly, it troubles me that, by imprudently and unnecessarily breaking from our sister courts of appeals . . . we are impeding Maryland’s and others’ reasonable efforts to prevent the next Newtown,” King wrote, listing other sites of recent mass shootings that concluded with San Bernardino, Calif.

Traxler, also a Clinton appointee, and Judge G. Steven Agee, an appointee of George W. Bush, acknowledged in their opinion the split with the other courts, saying, “We are not a rubber stamp.”

In an unusually pointed response to King, the judges also chastised their colleague for seeming to infer “that we will bear some responsibility for future mass shootings. In our view inferences of this nature have no place in judicial opinions and we will not respond beyond noting this.”

Specifically, the court’s opinion Thursday directs U.S. District Judge Catherine C. Blake, who sits in Baltimore, to apply a strict standard of legal review when considering the government’s interest in protecting public safety.

Chris Cox, the executive director of the National Rifle Association’s Institute for Legislative Action, said in a statement Thursday that the “highest level of judicial scrutiny should apply when governments try to restrict our Second Amendment freedoms.”

Gov. Larry Hogan (R) also opposed the ban when it passed the Maryland legislature, but has said he now accepts it as state law. Hogan’s spokesman declined to comment Thursday.

Frosh said the state would either ask for a rehearing of the case by the full 4th Circuit or seek review from the Supreme Court.

The Supreme Court has so far declined to take up the question of whether cities and states can prohibit these types of weapons after its landmark 2008 decision that declared an individual right to keep a firearm in the home.

Staff writer Ovetta Wiggins contributed to this report.