A federal judge on Monday blocked the Trump administration from implementing a voter verification system that would combine Social Security information with citizenship records, ruling that the effort unlawfully exposed sensitive personal data and led to eligible voters being wrongly flagged as noncitizens.

U.S. District Judge Sparkle Sooknanan, who is based in Washington, D.C., halted the administration’s modified Systematic Alien Verification for Entitlements, or SAVE, database, concluding that federal officials violated privacy protections and enabled states to improperly remove voters from registration rolls.