A U.S. judge strongly rebuked the Trump administration on Wednesday by rejecting a request by the Justice Department to temporarily block California from counting mail ballots for the midterm elections from more than 20,000 registered voters the department alleges are likely noncitizens.

The decision marks the latest setback for President Donald Trump's effort to boost the federal government's role in elections ahead of the November 3 midterms, with his Republican Party locked in a tight battle to retain control of both houses of Congress.

US District Judge David Carter issued the decision after a hearing on Tuesday in Los Angeles federal court over the Justice Department's request for a temporary restraining order barring officials from counting any ballots from the individuals it flagged.

The Justice Department's lawsuit, filed on October 15, was a rare intervention in the voting process weeks before an election and signaled the Trump administration's willingness to contest the midterm results in court.

"Never before in American history has the federal government, on the eve of an election, sought to coerce a state and local government to abandon their own Constitutional elections procedures and bend to the will of the Executive Branch," Carter wrote on Wednesday.

The judge, an appointee of Democratic President Bill Clinton, said the Justice Department's last-minute request to exclude over 20,000 ballots ran afoul of "longstanding constitutional principles mandating that states have control over their elections."

Carter warned that a ruling in the Trump administration's favor would "wreak havoc" and cause thousands of registered voters to "potentially lose the right that generations of Americans have fought to preserve."

"Eroded trust in our democracy is irreparable," Carter wrote. "Once a vote is segregated, lasting harm has occurred. If the Executive can discount votes and threaten an ongoing election due to unproven allegations, then our democracy is in danger." The Justice Department swiftly appealed the decision to the 9th US Circuit Court of Appeals.

"Every day, more ballots are processed by election officials," Justice Department lawyer Bill Essayli said in a statement. "This ongoing emergency disenfranchises American citizens through dilution." California has said the state's safeguards against noncitizen voting are robust. It said the Justice Department's assertions relied on "suspect data" and that complying with its demands would risk disenfranchising eligible voters.

California is the most populous US state and a Democratic stronghold. It has more seats in the House of Representatives — 52 — than any other state.

Trump has made California a focal point of his sweeping immigration crackdown since returning to the White House, accusing it of undermining public safety through its "sanctuary state" policies that limit cooperation with federal immigration enforcement.

Trump has repeatedly insisted that states are not doing enough to stop voting by noncitizens, which he says is widespread despite multiple studies and state audits showing it is rare.

Appeals court rejected emergency request Carter ruled two days after a federal appeals court on Monday rejected an unusual emergency request by the Justice Department asking the appeals court to temporarily block California from counting the ballots before Carter had the chance to rule.

The Justice Department did not indicate how many of the more than 20,000 people it flagged in California had actually submitted a mail ballot.

It had argued that a restraining order was necessary to ensure that California did not impede prosecutors' ability to enforce a federal law that makes it illegal for noncitizens to vote in federal elections.

But Carter said the Justice Department never explained why counting ballots would impair any prosecutions under the law, as states are not required to help the federal government investigate and prosecute crimes.

Apart from California, the Trump administration has sought to intervene in elections in two states that are home to competitive races.

In Alaska, the Justice Department last week asked a judge to prevent certification of election results if the Republican incumbent senator loses by a slim margin, alleging that the presence of another candidate with a similar name on the ballot could confuse voters. Alaska has urged that the case be dismissed, arguing it has taken steps to distinguish the two candidates on the ballot.

In Washington state, the Justice Department on Monday sent a letter asking officials not to count any ballots received from 400 voters it said may not be citizens. Washington's top elections official said the timing of the request indicated it was intended to cast unfounded suspicion on election results.

California had 23 million registered voters as of December 2025, while Washington had 5 million registered voters as of 2024, state records show.

Voting rights activists have expressed concern that the federal government's methods for scrutinizing state voter lists to identify noncitizen voters risk wrongly flagging naturalized citizens for removal from the rolls.