In a 39-page ruling, a panel of the U.S. Court of Appeals for the Ninth Circuit ruled 2-1 that it declines the administration's "invitation to contravene the Elections Clause by undermining the Constitution's plain text."

"If the United States believes different procedures are necessary for vote-by-mail ballots, we believe it should take that suggestion to Congress, not the courts," the majority stated.

A district court judge already denied that request and said that the Department of Justice's (DOJ) demands could disenfranchise citizens.

Referring to that ruling, the appeals court wrote, "As the district court found - and we discern no clear error - there is no feasible way to identify and segregate the ballots of specific individuals without potentially catastrophic effects on the entire system."

The panel rejected the government's emergency request for an injunction that would have barred the 20,000 ballots from being tallied until the voters' citizenship was verified. The midterm elections are set to be held on Tuesday, Nov. 3.

The Trump administration said it believes that the suspected noncitizens have already received mail-in ballots for the midterms and that if California officials receive those ballots, mix them with legitimate ones, and process them, illegal votes will be counted.

California officials have described the list as highly unreliable, saying it likely includes many people who are U.S. citizens.

State and county officials confirmed they lacked the mechanisms and authority to prevent non-U.S. citizens from voting in the elections, the DOJ wrote in its lawsuit earlier this month, meaning those individuals could potentially illegally vote in the election.

"As defendants continue processing ballots that cannot later be segregated or verified for eligibility, the dilution of lawful votes accelerates in real time," the DOJ said on Oct. 21 in an emergency filing to the appeals court.

Los Angeles County filed a motion asking the district judge to dismiss the lawsuit and argued that the DOJ lacked the legal standing to bring it.