Opponents of gerrymandering are breathing a sigh of relief today — the Supreme Court has upheld Arizona voters' decision to let an independent commission, rather than their legislature, draw their state's congressional districts.

The 5-4 decision, in Arizona State Legislature v. Arizona Independent Redistricting Commission, found that even though the US Constitution says the "Legislature" of each state should determine the time and manner of elections, the people of a state are allowed to vote via ballot initiative to take the powers of redistricting away from their legislature, and hand it over to an independent commission.

"The people of Arizona turned to the initiative to curb the practice of gerrymandering," Justice Ruth Bader Ginsburg wrote in her majority opinion, which was joined by the Court's other three liberals and Justice Anthony Kennedy. "In so acting, Arizona voters sought to restore 'the core principle of republican government,' namely, 'that the voters should choose their representatives, not the other way around.'"

But in a strongly-worded dissent, Chief Justice John Roberts and three of the court's conservatives said, essentially, that "Legislature" means "Legislature," and that the other justices were performing "a magic trick" to pretend otherwise. "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 wrote. "No matter how concerned we may be about partisanship in redistricting, this Court has no power to gerrymander the Constitution."

The decision upholds the status quo — both for Arizona, and, by implication, for other states that use outside commissions to draw their districts. If it had gone the other way, it could have had huge implications for how Congressional districts are drawn across the country.

The case hinged on what the US Constitution means by "legislature"

In 2000, Arizonans voted to amend their state constitution to take the redistricting process away from their state legislature, and hand it over to an independent redistricting commission. The change was made for state and congressional races. Then, over a decade later, the Republican-controlled legislature, frustrated with the commission's handling of the post-2010 congressional redistricting process, sued to try and get its control back.

Their argument was simple: Article I, Section 4 of the US Constitution says that state legislatures determine how House elections are held — so, the legislature says, it would be unconstitutional for that power to be stripped away from them through a statewide vote, without giving the legislature a say. Here's what the US Constitution says:



The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof...

However, the defendants argued that "Legislature" doesn't refer only to the legislature, but rather the broader lawmaking power of the state's people — and could therefore encompass statewide initiatives or referenda, like the one that was used to amend Arizona's constitution in this case. During oral arguments, Justice Elena Kagan also pointed out that other states have changed their "manner of holding elections" through a statewide vote with no legislative input — for instance, Mississippi enacted voter ID requirements, and Oregon moved to a vote-by-mail system.

Arizona's legislature wasn't completely powerless in the new process. In fact, four of the commission's five members are chosen by state legislative leaders (one each by the House and Senate leader of each party). But they did have to choose each member from a preexisting list of candidates compiled by the state's Commission on Appellate Court Appointments. And the fifth member — the chair — is chosen by the four other commissioners from that list.

The legislature was powerless, however, in deciding whether the new system should have been adopted at all. It was the state's voters who made that decision, not them. That's why GOP legislative leaders — unhappy with how the 2012 redistricting process went for their party — filed suit to try to regain their lost authority.

The case could have taken away one of states' best tools for fighting gerrymandering

The implications of the Arizona legislature's argument were radical, and a big threat to opponents of gerrymandering. The main reason districts are so often designed for partisan purposes in the US is because partisan state legislatures do the designing. So putting outside commissions in charge is the most common proposal to reform all this.

But Arizona's legislature argued that voters can't take redistricting away from the legislature, through a statewide vote. The US Constitution says state legislatures set the terms of elections, and that there's nothing the people of any state can do to change that, their argument went.

California's many, many House seats could also have been impacted

Though Arizona only has nine House seats, the case also had the potential to have a huge short-term impact because any ruling overturning Arizona's commission could have had implications for a similar one in California.

There are five other states — California, Idaho, Washington, Hawaii, and New Jersey — that use commissions to draw their congressional districts, according to Professor Justin Levitt of Loyola Law School. Some of these systems have been in place for decades. Other states give an advisory commission some role in a process where the legislature is still the primary actor.

But the impact on California would have been most consequential because of its sheer size — its 53 congressional districts make up 12 percent of the House of Representatives. The state had only just adopted a redistricting commission recently, and the outcome of its first go at a commission-controlled process was generally viewed as a success.