U.S. District Judge Loretta Biggs slammed an ongoing North Carolinian voter purge during a dramatic Wednesday hearing, telling county attorneys that she was “horrified” by the “insane” process by which voters could be removed from the rolls without their knowledge. “It almost looks like a cattle call, the way people are being purged,” Biggs said. “This sounds like something that was put together in 1901,” when the state used Jim Crow laws to prevent black citizens from casting a ballot.

Biggs called a hearing after the NAACP sued several North Carolina counties for purging nearly 6,700 voters—most of them black Democrats—from the rolls. These purges were legal under a state law that permits any person to revoke any other person’s voting rights. The process is simple: An individual gathers mail that was returned as undeliverable, then challenges the voter registration of residents at those addresses. If those voters do not appear at a county board of elections or return a notarized form, their voting rights are nullified.

In several North Carolina counties, Republican activists have used this process to revoke thousands of people’s voting rights at once, a majority of them minorities. But as the Justice Department noted in supporting the NAACP’s lawsuit, this process is illegal under federal law, which trumps state law when the two clash. Biggs indicated that she would halt the purges and restore purged voters’ rights under federal law but did not issue a ruling from the bench. Her decision is likely to come within the next few days.

In recent weeks, the North Carolina voter purges have drawn nationwide outcry as the most explicit example of Republicans suppressing minority voting rights. Even President Barack Obama mentioned the purges while campaigning in the state on Wednesday. Obama told the story of 100-year-old Grace Bell Hardison, a black woman whom Republican activists attempted to purge from the voter rolls. “If you don’t vote,” he told supporters, “then you’ve done the work of those who would suppress your vote without them even having to lift a finger.”