The justices voted 5-4 to reject a constitutional challenge from Arizona's Republican lawmakers to the commission that the state's voters created in 2000. Among the other states affected is California, which uses an independent commission to draw electoral boundaries for its largest-in-the-nation congressional delegation.
"Arizona voters sought to restore the core principle that the voters should choose their representatives, not the other way around," Justice Ruth Bader Ginsburg said in her opinion for the court.
Ginsburg said that there is "no constitutional barrier to a state's empowerment of its people by embracing that form of lawmaking." Justice Anthony Kennedy and Ginsburg's three liberal colleagues joined her opinion.
In dissent, Chief Justice John Roberts accused the majority of approving a "deliberate constitutional evasion."
"The court's position has no basis in the text, structure, or history of the Constitution, and it contradicts precedents from both Congress and this court," Roberts said. Justices Samuel Alito, Antonin Scalia and Clarence Thomas signed onto Roberts' opinion.
The Arizona case stemmed from voters' action in 2000. The legislature's Republican leaders filed their lawsuit after the commission's U.S. House map in 2012 produced four safe districts for Republicans, two for Democrats and made the other three seats competitive. Democrats won all three in 2012, but the Republicans recaptured one last year.
The argument against independent commissions rests in the Constitution's Election Clause, which gives state legislatures the power to set "the times, places and manners of holding elections for senators and representatives."
States are required to re-draw maps for congressional and state legislative districts to account for population changes after the once-a-decade census.
Some states have sought to rein in lawmakers' power over drawing political boundaries because the justices have been unwilling to limit excessive partisanship in redistricting, known as gerrymandering. A gerrymander is a district that is intentionally drawn, and sometimes oddly shaped, to favor one political party.
Analysts said Monday's decision could open the door to efforts in other states to create independent commissions to redraw congressional lines.
That would be likeliest in the 24 states that already use ballot initiatives, which let citizens bypass legislatures and directly put questions to voters, usually by collecting signatures on a petition.
"It leaves open the freedom for voters in states to experiment with ways to make their democracy better," said Michael Li, counsel at the New York University Law School's Brennan Center for Justice, which filed a brief supporting Arizona's commission.
Republicans employed an enormously successful strategy to take advantage of the 2010 census, first by winning state legislatures and then using that control to draw House districts to maximize their power. One measure of their success: In 2012, Republicans achieved a 33-seat majority in the House, even though GOP candidates as a group got 1.4 million fewer votes than their Democratic opponents.
Independent commissions such as Arizona's "may be the only meaningful check" left to states that want to foster more competitive elections, the Obama administration said.
Only Arizona and California essentially remove the legislature from the process, the National Conference of State Legislatures said in a brief supporting the Arizona GOP lawmakers' challenge.
Lawmakers' only contribution in those two states is picking commission members from a list devised by others. In the other states - Connecticut, Hawaii, Idaho, Indiana, Iowa, Maine, Montana, New Jersey, New York, Ohio and Washington state - lawmakers either get first crack at drawing districts, approve plans drawn by commissions or appoint commission members of their choosing, the conference said.
Supporters of the commissions point to more competitive races in both Arizona and California since these entities were created.
The case is Arizona State Legislature v. Arizona Independent Redistricting Commission, 13-1314.
Associated Press writer Alan Fram contributed to this report.
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