The U.S. Supreme Court vacated a ruling that criminalized stun guns by excluding them from Second Amendment protections. In 2011, a Massachusetts woman, Jaime Caetano, was arrested for carrying a stun gun in her purse to protect herself from her abusive ex-boyfriend. A judge at the time ruled that Caetano’s decision to carry a stun gun was illegal because the Second Amendment right to bear arms only applies to the types of weapons commonly used at the time the amendment was ratified. Last year, the Supreme Judicial Court of Massachusetts upheld Caetano’s criminal conviction, saying that a stun gun “is...