A federal judge in California has ordered the Trump administration to stop threatening state and local election officials with criminal charges over their handling of election ballots.

Judge Trina Thompson ruled that the Department of Justice must cease demanding that state and local election officials set aside or refuse to process certain ballots that the administration alleges may have been cast by non-citizens.

The ruling comes days before the midterm elections on 3 November, which will determine which party controls the US Congress for the remaining two years of Donald Trump's presidency.

Earlier this month, the Justice Department sent letters to California's secretary of state and the Los Angeles County Registrar demanding they sequester the ballots of approximately 20,000 registered voters whom the administration "believe" are "likely" non-citizens, according to court documents.

About a week later, armed officials from the Department of Homeland Security delivered letters to county officials and employees across California, threatening criminal charges if they failed to comply.

Election officials said they could not meet those demands without violating procedures required by state and federal law. A judge rejected the demand, writing that it would "wreak havoc" on the election.

Around the same time, the Justice Department reportedly launched a criminal investigation into county election officials, issuing federal grand jury subpoenas.

Civil rights groups and unions representing election workers filed a legal complaint, accusing the Justice Department of interfering with the administration of the election. Judge Thompson then ordered the administration to halt its actions.

"Although Defendants claim that their actions are designed to halt unlawful voting by noncitizens, their actions are likely to have the effect of interfering with election administration and disenfranchising lawful voters," Judge Thompson wrote.

According to Thompson's order, the administration sent a similar letter to Washington state, demanding that its secretary of state stop processing ballots linked to alleged non-citizen voters.

The moves are part of a years-long campaign by Trump and his allies to combat alleged widespread voter fraud. Trump has alleged "rampant" cheating in postal voting and claimed non-citizens are voting in large numbers. He also offered a $1 million reward to anyone who reports a case of voter fraud that leads to a conviction.

Research, however, indicates that such fraud is extremely rare. According to reports, the Heritage Foundation's database identified 24 cases of non-citizens convicted for voting between 2005 and 2025.

Trump criticised the rulings on Saturday, writing: "Why would they reject fixing Election Fraud?" He vowed to continue fighting for what he called "Election Integrity."