A split Supreme Court declined on Monday to hear a challenge to a state ban on assault weapons and semiautomatic rifles that are popular among gun owners and that have also been used in multiple mass shootings.

The court’s decision means Maryland’s ban on assault-style weapons remains in effect.

The majority did not explain its reasoning in turning down the case, as is typical. But three conservative justices on the nine-member court publicly noted their disagreement, and a fourth said he is skeptical that such bans are constitutional.

Justices Samuel Alito and Neil Gorsuch said they would have taken the case, and Justice Clarence Thomas wrote separately to say the law likely runs afoul of the Second Amendment.

“I would not wait to decide whether the government can ban the most popular rifle in America,” Thomas wrote. “That question is of critical importance to tens of millions of law-abiding AR–15 owners throughout the country.”

Justice Brett Kavanaugh agreed with the decision to pass on the case now, but he said that he is skeptical that such bans are constitutional and that he expects the court will address the issue “in the next term or two.”

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The Maryland law was passed after the 2012 shooting at Sandy Hook Elementary School in Connecticut that killed 20 children and six adults. The shooter was armed with an AR-15, one of the firearms commonly referred to as an assault weapon.

Several states have similar measures, and congressional Democrats have also supported the concept. The challengers had argued that people have a constitutional right to own the firearms like the AR-15.

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The case comes three years after the high court handed down a landmark ruling that expanded Second Amendment rights and spawned challenges to firearm laws around the country.

Ten states and the District of Columbia have similar laws, covering major cities like New York and Los Angeles. Congress allowed a national assault weapons ban to expire in 2004.