The federal Motor Voter Act bars states from canceling registrations for inactivity.
But Alito maintained that OH does not base its decision to remove voters "solely" on their failure to vote but also on the failure to respond to the notice from elections officials. His case was backed by 12 generally Democratic-leaning states (pdf, p.33-35), and was opposed by the Trump administration and 17 typically Republican states (pdf, p.21-22).
"Literally every other state uses a different, and more voter-protective, practice", the group added.
After the last presidential election, the department switched sides in the case, Husted v. A. Philip Randolph Institute, No. 16-980. But other states may now follow Ohio's lead.
The subtext of Monday's ruling decision was a continuing battle between Republicans and Democrats over laws that regulate who gets to vote and when, including voter-ID requirements and restrictions on early voting.
While much of the nation's attention is on how Donald Trump is sabotaging America overseas, his Supreme Court nominee Neil Gorsuch used his stolen seat to cast the deciding vote in a 5-4 decision damaging our democracy here at home.
Twelve states, generally led by Democrats, filed a brief supporting Mr. Harmon.
At least 846,391 OH voter registrations were canceled between 2010 and 2014, according to the U.S. Election Assistance Commission.
But in recent years, some purges have been viewed through a more partisan lens.
ACLU voting rights attorney Dale Ho pointed out on Monday's teleconference call that there was already another anti-voter purge lawsuit underway that includes an issue not addressed in the OH case. Alabama put 340,000 voters on its inactive list the same year. And there was no doubt that OH - which has purged 2 million voters since 2011 on various pretexts - would aggressively pursue whatever avenues the courts allowed for restricting the franchise, which happens to benefit the party that has run Ohio's electoral machinery during this period.
The US Supreme Court sided with the OH in a case over whether or not the state has the right to cull voters from registers if they go too long without casting a ballot.
Thus, the process of removing a voter takes about six years. "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". "Thirty-eight other states (and the District of Columbia) have established practices that, unlike Ohio's supplemental process, use independent information that an individual has moved - not an individual's failure to vote - as a trigger to send a Section 8 (d)(2) notice". But she said she anxious that advocates of more restrictive voting policies might see the decision as an opening to further crack down on inactive voters. The challengers called Ohio's policy the most aggressive.
In any event, today's ruling empowers local officials to ensure the most accurate and reliable voter rolls possible.
The Crosscheck program, which involves 26 states around the country, has come under increasing scrutiny in recent years as some states accuse it of improperly flagging eligible voters. If they do nothing, their names eventually fall off the list of registered voters.
Tennessee has eliminated the practice of purging voters based on a lapse in voting history. An appellate court sided with the purged voters, but now the Supreme Court has overturned that ruling.