The U.S. Justice Department filed a lawsuit against California on October 15, seeking to block the state from counting mail-in ballots in the upcoming November 3 midterm elections from more than 20,000 voters whom the federal government identifies as likely noncitizens. The Trump administration argued that these ballots should not be tabulated until the immigration status of these individuals is verified.

The lawsuit, filed in federal court in Los Angeles, represents an intensification of the federal government’s efforts to address alleged voting by noncitizens, a practice which is illegal but has been widely debated. The Department of Homeland Security reportedly identified the group of 20,000 based on a comparison of California’s voter rolls with federal databases. The DOJ provided a password-protected thumb drive containing the list to Los Angeles County Registrar Dean Logan, but California officials expressed concerns about the security and legitimacy of the data and the process used to deliver it.

California Secretary of State Shirley Weber, who is named as a defendant along with Logan, pushed back against the government’s claims, stating that the federal government has not provided evidence to substantiate its allegations. Weber cited a previous instance in Nevada where a similar federal claim was disproven after state officials verified that those flagged as possible noncitizens were indeed U.S. citizens. She also noted that voting is already underway in California and criticized the Justice Department’s demands as unprecedented and lacking transparency.

California Attorney General Rob Bonta confirmed that state officials would not comply with the government’s request to withhold ballots from the alleged noncitizen voters. He highlighted the decline from an earlier DHS estimate of 190,000 noncitizens on the voter rolls to the 20,000 figure currently cited, questioning the accuracy of the initial numbers.

Experts on election law have expressed skepticism about the federal government’s authority over state-run elections, emphasizing that election administration is principally a state responsibility. Rick Hasen, a law professor at the University of California, Los Angeles, noted that the DOJ’s request could run afoul of federal law prohibiting mass voter roll purges within 90 days of an election. The Trump administration, however, contends that noncitizen removal should be exempt from such restrictions because those individuals were allegedly not legally eligible to register in the first place.

Voting rights advocates have also raised concerns that outdated federal data may wrongly flag naturalized citizens as noncitizens, risking disenfranchisement. The Justice Department has increased prosecutions related to noncitizen voting in recent months, yet studies indicate that such cases remain rare.

California elections officials pointed out the challenges and potential security risks in handling the thumb drive provided by the DOJ, with Logan stressing that election offices generally do not insert external drives into their systems due to cybersecurity protocols.

This legal conflict is the latest in a series of actions by the Justice Department seeking access to voter data and heightened scrutiny of voter rolls in multiple states. Although the department has pursued similar lawsuits against 30 states and the District of Columbia, it has largely faced defeats, losing most cases without securing court victories thus far.

The lawsuit underscores ongoing tensions between federal and state authorities over election oversight and the handling of voter eligibility ahead of a critical midterm election cycle, during which control of Congress remains closely contested.