Richard Wolf

USA TODAY

WASHINGTON — The Supreme Court on Monday unanimously reversed a Massachusetts court that had upheld banning stun guns, giving proponents of gun rights at least a temporary victory.

The justices ruled that the state court's reasons for upholding the law conflicted with the Supreme Court's 2008 decision upholding the right to bear arms for self-defense -- a ruling written by the late Justice Antonin Scalia in 2008.

The challenge, filed by a woman who was arrested for carrying the weapon in her purse for protection, now gets new life. But rather than hearing the case themselves and potentially striking down the ban, the justices sent it back to the state's Supreme Judicial Court.

They reasoned that their own landmark decisions in District of Columbia v. Heller and McDonald v. Chicago were meant to protect even firearms "that were not in existence at the time of the founding." However, they stopped short of a blanket endorsement of stun guns.

That did not satisfy Justices Samuel Alito and Clarence Thomas, who complained in a 10-page concurrence that the court's "grudging" decision to send the case back may not be enough to save Jaime Caetano and citizens like her "who must defend themselves because the state will not."

"If the fundamental right of self-defense does not protect Caetano, then the safety of all Americans is left to the mercy of state authorities who may be more concerned about disarming the people than about keeping them safe," Alito wrote.

The high court ruled in Heller that Americans can keep handguns in their homes for self-defense, and it made clear in McDonald that state and local governments cannot stop them. But the court limited its initial ruling to weapons that were commonly used at the time the Constitution was written.

The Massachusetts Supreme Judicial Court ruled unanimously in March that stun guns didn't fit that definition. It noted the first patent for a stun gun was filed in 1972, and the weapons were not sold commercially until the early 1990s.

"We therefore conclude that stun guns were not in common use at the time of the Second Amendment's enactment," Justice Francis Spina wrote. "Without further guidance from the Supreme Court on the scope of the Second Amendment, we do not extend the Second Amendment right articulated by Heller to cover stun guns."

The case dates back to 2011, when Caetano was arrested in a supermarket parking lot. She said she carried the stun gun for protection against an abusive former boyfriend who she previously had sought to avoid through restraining orders.

In seeking the high court's intervention, Caetano's lawyers argued that stun guns and Tasers are not lethal, unlike the types of firearms already permitted under prior Supreme Court rulings. They noted that Scalia's 5-4 ruling in Heller specified it could be applied to modern weapons.

"Some have made the argument, bordering on the frivolous, that only those arms in existence in the 18th century are protected by the Second Amendment. We do not interpret constitutional rights that way," Scalia wrote. "The Second Amendment extends ... to all instruments that constitute bearable arms, even those that were not in existence at the time of the founding."

Caetano's petition also contended that just seven states ban stun guns, while hundreds of thousands have been sold to private citizens across the United States. A Michigan court, it noted, ruled in favor of possession in a 2012 case.

Although Caetano was carrying the weapon in a parking lot, she was homeless at the time. For that reason, the case was unlikely to resolve the next major question on gun rights -- whether those permitted in the home can be carried in public.