The Supreme Court on Monday turned down an opportunity to weigh in on whether the government may restrict 18- to 20-year-olds from buying or carrying guns, a question that has divided the lower courts. The case concerned a Minnesota law that makes it a crime for people under 21 to carry guns in public. Last year, the Eighth Circuit struck down the law, ruling that the Second Amendment required letting those as young as 18 be armed. “The Second Amendment’s plain text does not have an age limit,” wrote Judge Duane Benton, who was appointed by President George W. Bush. He relied on the 26th Amendment, which lowered the voting age to 18 in 1971. The amendment, Judge Benton wrote, “unambiguously places 18- to 20-year-olds within the national political community.”