The Supreme Court has adopted a new interpretation of Americans’ right to vote: use it or lose it.

Ohio law allows state officials to strike voters from the rolls if they haven’t cast a ballot in three consecutive federal elections and fail to return a single piece of mail. In a 5-4 ruling on Monday, the court’s five conservative justices upheld the law. “We have no authority to second-guess Congress or to decide whether Ohio’s [law] is the ideal method for keeping its voting rolls up to date,” Justice Samuel Alito, concluded for the majority in Husted v. A. Philip Randolph Institute. “The only question before us is whether it violates federal law. It does not.”

Voting-rights groups said the ruling would keep lower-income and disadvantaged residents away from the polls. “Voters should not be purged from the rolls simply because they have exercised their right not to vote,” Dale Ho, the director of the ACLU’s Voting Rights Project, said in a statement. “This ruling is a setback for voting rights, but it is not a green light to engage in wholesale purges of eligible voters without notice.”

The ruling is a major victory for Republicans nationwide and could open the door to similar laws in other states. It also reifies efforts by GOP-controlled state legislatures to enact laws that make it harder for Americans to vote. Republicans typically defend these measures as necessary to combat voter fraud, but experts widely agree that fraud is rare. Many argue that the laws serve an altogether different purpose: preserving Republican electoral power by keeping disadvantaged and lower-income Americans away from the polls.

At issue in Monday’s case was how Ohio maintains its voter rolls. Every state takes steps to maintain its list of eligible voters. Americans can lose their eligibility to vote by dying, moving to a new jurisdiction, receiving a felony conviction, or some combination thereof. Ohio uses two methods to keep track of any changes. The first is to double-check voter addresses against the U.S. Postal Service’s change-of-address database. If there’s a match, the state then mails a notice to the original residence and strikes the voter from the rolls if they don’t reply or cast a ballot within four years.

Federal election laws are designed to allow this method, and most states use some form of it. But Ohio takes it a step further. To find ineligible voters who didn’t tell the Postal Service that they moved, the state also uses what it calls the “Supplemental Process”: Election officials mail notices to voters who have gone two years without casting a ballot, changing their voter registration, or otherwise engaging in what the state calls “voter activity.” If the voter doesn’t mail back the notice and doesn’t cast a ballot for the next four years, he or she is stricken from the rolls.

Ohio officials first adopted the Supplemental Process in 1994 and carried it out every two years until 2014, when a lawsuit by the conservative legal organization Judicial Watch compelled the state to conduct it on an annual basis. In 2015, Ohio resident Larry Harmon, who hadn’t voted since the 2008 presidential election, discovered he had been stricken from the voter rolls when he tried to cast a ballot in a state race. (State records say Harmon was sent a notice in July 2011, but he told the court that he doesn’t remember receiving one.) Harmon, the A. Philip Randolph Institute, and the Northeast Ohio Coalition for the Homeless filed a lawsuit in 2016 arguing that the state’s Supplemental Process violated federal election law.

Under the National Voter Registration Act of 1993, states can’t use inactivity as the sole reason to remove a voter from the rolls. Ohio officials argued that this prohibition doesn’t apply to the Supplemental Process because the state mails notices to voters before striking them from the rolls. The Sixth Circuit Court of Appeals disagreed, finding that the process “constitutes perhaps the plainest possible example of a process that ‘result[s] in’ removal of a voter from the rolls by reason of his or her failure to vote.”

The Supreme Court sided with Ohio’s interpretation of the law, overturning the Sixth Circuit’s ruling. The Supplemental Process “does not strike any registrant solely by reason of the failure to vote,” Alito wrote. “Instead, as expressly permitted by federal law, it removes registrants only when they have failed to vote and have failed to respond to a change-of-residence notice.”

That reasoning did not persuade the court’s four liberal justices. “Ohio, of course, says that it has a ground for believing that those persons they remove from the rolls have, in fact, changed their address, but the ground is the fact that the person did not vote—the very thing that the Failure-to-Vote Clause forbids Ohio to use as a basis for removing a registered voter from the registration roll,” Justice Stephen Breyer wrote in their dissent.

In a separate solo dissent, Justice Sonia Sotomayor addressed the disparate impact that Ohio’s law would have on the state’s electorate. Multiple organizations filed briefs with the court, she observed, to note that “that the Supplemental Process has disproportionately affected minority, low-income, disabled, and veteran voters.” One brief contended that 10 percent of voters in majority-black neighborhoods in Cincinnati had been removed for inactivity under the process.

The impact can be substantial for those affected. “At best, purged voters are forced to ‘needlessly reregister’ if they decide to vote in a subsequent election; at worst, they are prevented from voting at all because they never receive information about when and where elections are taking place,” Sotomayor wrote.

Other Republican-backed voter measures impose similar burdens. More stringent voter ID laws suppress black and Hispanic voter turnout, academic studies have consistently shown. Since voters from those groups tend to support Democratic candidates, Republican nominees typically reap the benefits.

Brad Schimel, Wisconsin’s attorney general, defended his state’s voter-ID law last month as a means to ensure Republican candidates would prevail. “How many of your listeners really honestly are sure that Senator [Ron] Johnson was going to win re-election or President Trump was going to win Wisconsin if we didn’t have voter ID to keep Wisconsin’s elections clean and honest and have integrity?” he asked a radio-show host during an interview last month. Trump won the state in 2016 by 22,000 votes.

Sotomayor was careful not to single out any state laws that might come under future scrutiny from the court. But the breadth of her call to arms was unmistakable. “Communities that are disproportionately affected by unnecessarily harsh registration laws should not tolerate efforts to marginalize their influence in the political process,” she wrote, “nor should allies who recognize blatant unfairness stand idly by.”