A major Supreme Court battle over whether states can ban AR-15-style semiautomatic rifles has been thrown into uncertainty.

Problems arose with the case after the lead plaintiff unexpectedly asked to withdraw from it, CNN reported over the weekend.

The unusual development involves Snope v. Brown, a closely watched Second Amendment challenge to Maryland’s prohibition on certain semiautomatic firearms commonly described by the state as assault weapons.

The Supreme Court agreed in June to hear the case, setting up a potentially consequential ruling on the constitutional limits of state gun restrictions.

But attorneys informed the justices last week that lead plaintiff Dominic Bianchi wanted to be dismissed from the litigation.

The request immediately prompted Maryland Attorney General Anthony Brown’s office to argue that the entire case should now be dismissed.

Maryland told the Supreme Court Thursday that Bianchi’s departure raises questions about whether the remaining plaintiffs have the legal standing necessary to continue challenging the law.

The case also includes other individual plaintiffs and organizations, including the Firearms Policy Coalition and Second Amendment Foundation.

Those groups maintain that Bianchi’s withdrawal does not eliminate the underlying constitutional dispute.