WASHINGTON (Reuters) - The U.S. Supreme Court on Monday revived Ohio’s contentious policy of purging infrequent voters from registration rolls in a ruling powered by the five conservative justices and denounced by liberal Justice Sonia Sotomayor as an endorsement of the disenfranchisement of minority and low-income Americans.

In a 5-4 decision in the closely watched voting-rights case, the high court overturned a lower court’s ruling that Ohio’s policy violated a 1993 federal law enacted to make it easier to register to vote. All four liberal justices dissented, and top Democrats said the decision will boost what they called Republican voter-suppression efforts. But other states may now follow Ohio’s lead.

Voters purged from registration rolls who challenged the policy in the Republican-governed state argued that the practice illegally erased thousands of voters from registration rolls and disproportionately impacted racial minorities and poor people who tend to back Democratic candidates.

The state said the policy was needed to keep voting rolls current, removing people who have moved away or died.

Under Ohio’s policy, if registered voters miss voting for two years, they are sent registration confirmation notices. If they do not respond and do not vote over the following four years, they are purged.

“This decision is validation of Ohio’s efforts to clean up the voter rolls and now with the blessing (of the) nation’s highest court, it can serve as a model for other states to use,” Republican Ohio Secretary of State Jon Husted said.

Five other states also remove voters from their registration lists for failure to vote. The challengers called Ohio’s policy the most aggressive.

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Writing for the majority, Justice Samuel Alito said the court was not deciding whether Ohio’s policy “is the ideal method for keeping its voting rolls up to date. The only question before us is whether it violates federal law. It does not.”

Many states over the decades had erected barriers to voting, sometimes targeting black voters. The National Voter Registration Act (NVRA) among other provisions had forbade removing voters from registration lists for failing to vote.

In a dissenting opinion, Sotomayor said the ruling “ignores the history of voter suppression against which the NVRA was enacted and upholds a program that appears to further the very disenfranchisement of minority and low-income voters that Congress set out to eradicate.”

A 2016 Reuters analysis found roughly twice the rate of voter purging in Democratic-leaning neighborhoods in Ohio’s three largest counties as in Republican-leaning neighborhoods.

‘BLATANT UNFAIRNESS’

“Communities that are disproportionately affected by unnecessarily harsh registration laws should not tolerate efforts to marginalize their influence in the political process, nor should allies who recognize blatant unfairness stand idly by,” added Sotomayor, the first Hispanic Supreme Court justice.

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The challengers criticized what they called Ohio’s “use it or lose it” policy that they said violated registered voters’ right to choose when to vote, noting that some voters do not cast a ballot when they do not support any of the candidates running.

Republican President Donald Trump’s administration backed Ohio, reversing the stance taken by Democratic former President Barack Obama’s administration against the policy, and welcomed the ruling. Democrats disagreed.

“Democracy suffers when laws make it harder for U.S. citizens to vote,” top Senate Democrat Chuck Schumer said.

“This wrongly decided decision paves the way to mass disenfranchisement in Ohio and around the country,” top House of Representatives Democrat Nancy Pelosi added.

The challengers, represented by liberal advocacy group Demos and the American Civil Liberties Union, sued Husted in 2016 to end the policy. One of the lead plaintiffs was U.S. Navy veteran Larry Harmon, who was blocked from voting in a 2015 marijuana-legalization initiative.

“If states take today’s decision as a sign that they can be even more reckless and kick eligible voters off the rolls, we will fight back in the courts, the legislatures and with our community partners across the country,” Demos attorney Stuart Naifeh said.

The ACLU’s Dale Ho said the ruling “is not a green light to engage in wholesale purges of eligible voters without notice.”

Conservative advocacy groups praised the ruling.

“Leftists opposed to election integrity suffered a big defeat today. Frankly, this and their other assaults on clean election measures suggest the organized left and their politician allies want to be able to steal elections if necessary,” Judicial Watch President Tom Fitton said.

Liberal Justice Stephen Breyer, in a dissent joined by the other liberal justices, said, “Using a registrant’s failure to vote is not a reasonable method for identifying voters whose registrations are likely invalid.” Since people tend not to send confirmation notices back to the government, it is not a reliable way to determine whether someone has moved away, Breyer added.

Ohio’s policy would have barred more than 7,500 people from voting in the 2016 presidential election had the lower court not blocked it, according to court papers.

For graphic on major cases before the U.S. Supreme Court, click: tmsnrt.rs/2Mjahov