In a 5-4 decision handed down today, the Supreme Court decided the existence of the Arizona Independent Redistricting Commission—a panel created by Arizona voters in 2000 to reduce partisan interference in the state’s drawing of congressional districts—is in fact constitutional.

Members of the Arizona State Legislature sued A.I.R.C. in 2012 after the commission submitted redrawn congressional maps that some legislators believed were unfairly advantageous to Democrats. The legislators asserted that the A.I.R.C. violated the U.S. Constitution’s elections clause, Article 1 of Section 4, which empowers “the legislature” of individual states to draw congressional boundaries.

The author of the court’s majority opinion, Justice Ruth Bader Ginsberg, wrote that “lawmaking power in Arizona includes the [ballot] initiative process” and that “we see no constitutional barrier to a State’s empowerment of its people by embracing that form of lawmaking.”

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