“The amendment resulted from an arduous, decadeslong campaign in which reformers across the country worked hard to garner approval from Congress and three-quarters of the states,” the chief justice wrote. “What chumps! Didn’t they realize that all they had to do was interpret the constitutional term ‘the legislature’ to mean ‘the people’?”

Chief Justice Roberts said it was not clear that the independent commission in Arizona was above partisanship. In any event, he said, the Constitution settled the question presented in the case.

“Like most provisions of the Constitution, the elections clause reflected a compromise — a pragmatic recognition that the grand project of forging a union required everyone to accept some things they did not like,” he wrote. “This court has no power to upset such a compromise simply because we now think that it should have been struck differently.”

Justices Antonin Scalia, Clarence Thomas and Samuel A. Alito Jr. joined the chief justice’s dissenting opinion.

In a joint statement, the speaker of the Arizona House, David Gowan, and the Senate president, Andy Biggs, both Republicans, said: “We are disappointed that the Supreme Court has decided to depart from clear language of the Constitution. The Framers selected the elected representatives of the people to conduct congressional redistricting. It’s unfortunate that the clear constitutional design has been demolished in Arizona by five lawyers at the high court.”

Paul F. Eckstein, a lawyer with Perkins Coie in Phoenix who in 2002 represented a group of Latinos seeking to make the districts created by the commission at the time more competitive, called the opinion “a ringing endorsement for the use and power of voter initiatives, which not every state has.”

In a second dissent on Monday, Justice Scalia, joined by Justice Thomas, said he would have dismissed the case because the State Legislature lacked standing to sue.

“Normally, having arrived at that conclusion, I would express no opinion on the merits,” Justice Scalia wrote. “In the present case, however, the majority’s resolution of the merits question (‘legislature’ means ‘the people’) is so outrageously wrong, so utterly devoid of textual or historic support, so flatly in contradiction of prior Supreme Court cases, so obviously the willful product of hostility to districting by state legislatures, that I cannot avoid adding my vote to the devastating dissent of the chief justice.”