The U.S. Supreme Court suggested that people have a constitutional right to carry stun guns, unanimously ruling in favor of a Massachusetts woman convicted of carrying a weapon that she said she needed for protection from her ex-boyfriend.

In an unsigned, five-paragraph ruling, the justices set aside a lower court decision that upheld a Massachusetts ban on stun-gun possession. Although the high court didn’t explicitly strike down the ban, the justices said the reasoning used by Massachusetts’s top court was flawed.

The decision marks the first time the four liberal justices have acquiesced in a decision applying the individual Second Amendment rights recognized by the court in 2008.

“Today’s decision suggests the court is not eager to overturn earlier decisions protecting gun rights,” said Adam Winkler, a professor at the University of California at Los Angeles School of Law and the author of a book on the history of the gun-rights battle. The ruling is a “clear affirmation” of the 2008 decision, he said.

The ruling is a victory for Jaime Caetano, who didn’t serve any jail time and now may be able to get the conviction thrown out. The Supreme Court sent the case back to a Massachusetts court without directly saying what should happen with Caetano’s conviction.

Heller Ruling

The Massachusetts Supreme Judicial Court, the state’s highest tribunal, said stun guns aren’t the type of weapons protected by the Second Amendment.

The justices said the state court’s reasoning couldn’t be squared with the landmark 2008 Heller v. District of Columbia decision. The Supreme Court said that, under the Heller ruling, weapons can qualify for Second Amendment protection even if they didn’t have a military use and weren’t in common use when the amendment was enacted.

“The explanation the Massachusetts court offered for upholding the law contradicts this court’s precedent,” the Supreme Court said.

Two justices, Samuel Alito and Clarence Thomas, issued a 10-page concurrence that used far more sweeping language, saying the Massachusetts ruling “poses a grave threat to the fundamental right of self-defense.”

Alito said Caetano obtained the stun gun only after court-issued restraining orders failed to protect her from the ex-boyfriend.

“By arming herself, Caetano was able to protect against a physical threat that restraining orders had proved useless to prevent,” Alito wrote. “And, commendably, she did so by using a weapon that posed little, if any, danger of permanently harming either herself or the father of her children.”

Five states, including New York and New Jersey, and more than a dozen cities and towns ban the possession of stun guns, according to Eugene Volokh, a UCLA law professor who filed a brief urging the high court to review the case. He said he was “pleasantly surprised” by the summary reversal.

“It’s really quite remarkable,” he said. “It does seem that the court is willing, at least in certain kinds of cases, to uphold the right to bear arms.”

The case is Caetano v. Massachusetts, 14-10078.