ALSO SEE: Supreme Court Lets Trump Administration Use Revamped Federal Voter Eligibility Database for Now

Critics of the Trump administration system to monitor the citizenship status of voters had raised alarms about privacy and improper voter purges.

The Supreme Court ruled on Friday that the Trump administration can deploy an expansive online system that combines citizenship information, Social Security numbers and other sensitive data about millions of Americans, including to allow states to use it to hunt for ineligible voters.

Critics fear that using the system could result in the purging of large numbers of valid voters from state rolls, if states choose to use it ahead of the midterm elections.

The majority concluded that a lower-court ruling that had blocked the Trump administration from rolling out the system was improper because it inhibited “the federal government’s efforts to assist state and local agencies in the proper administration of the midterm elections.”

The emergency ruling was unsigned and gave no vote count, but the court’s three liberal justices joined in dissent. The ruling was a victory for the Trump administration as it tries to marshal the resources of the federal government to shape who can vote, and how. The effort has prompted legal challenges ahead of November’s midterm elections.

In a 12-page dissent, Justice Ketanji Brown Jackson emphasized that the majority’s decision created the conditions for some states to cancel the voter registrations of at least some recently naturalized citizens or to force them to provide proof of citizenship before voting.

“The harm caused by burdening or disenfranchising even a few lawful voters outweighs the nonexistent harm that the government experiences when it is prevented from taking an action that it likely lacks the authority to take,” she wrote, joined by Justices Sonia Sotomayor and Elena Kagan.

The decision came after the justices had dealt the administration a major setback this month, when the court’s majority blocked the government’s plan to require the Postal Service to screen mail-in ballots.

That loss frustrated President Trump, who assailed the court in a social media post, accusing it of “shockingly bad rulings that are of such magnitude that it won’t be easily possible for our Country to recover or heal.”

In March 2025, Mr. Trump signed an executive order directing several federal agencies, including the Department of Homeland Security and the Social Security Administration, to pool their records into an online tool that state and local officials could use to verify the citizenship and immigration status of registered voters.

It is illegal for noncitizens to vote in federal elections. Mr. Trump has long claimed, without evidence, that large numbers of noncitizens have managed to register and then illegally vote.

Mr. Trump’s directive prompted the Department of Homeland Security to overhaul the Systematic Alien Verification for Entitlements system, which had long been used by local, state and tribal agencies to check the citizenship and immigration status of people seeking some types of benefits and licenses. The expanded system pulled in Social Security data and other records.

Several legal challenges followed, including a lawsuit by voting rights groups.

In June, a federal judge in Washington blocked the Trump administration from allowing states to use the online system to screen their voter rolls.

Judge Sparkle L. Sooknanan, who was appointed by President Joseph R. Biden Jr., found that in “scrambling to comply with an executive order aimed at reshaping federal elections,” federal agencies “haphazardly combined and repurposed the private information of millions of Americans, including citizenship data that they knew to be unreliable.”