On Friday President Donald Trump warned California election officials that they will go to prison if they count mail-in ballots from about 20,000 people who have been identified as possible noncitizens by the federal government, intensifying the legal dispute with the state mere weeks before the midterm elections.

California's voter registration system relies on applicants attesting to their own citizenship, and county officials argued that the system obligates them to count ballots from registered voters. The Trump administration disagrees.

"They will all go to jail for a long period of time!!!" Trump wrote on Truth Social on Oct. 16. He attached a copy of a Justice Department letter to Los Angeles County that promised "significant" consequences for "facilitating or ignoring" noncitizens voting in a federal election.

"The legal consequences for either facilitating or ignoring a federal crime are significant," the letter reads. "Noncitizen voting in a federal election is a federal crime-and knowingly facilitating such conduct is equally unlawful. Under 18 U.S.C. § 611(a), noncitizens are prohibited from voting in any election involving federal offices."

The letter continued:

Under 18 U.S.C. § 2, anyone who aids, abets, counsels, induces, or procures the commission of a federal offense is equally liable. If persons knowingly tabulate ballots cast by individuals identified by federal agencies as noncitizens, they risk becoming aiders and abettors to a federal crime. Your assertion that ballots must be counted simply because California's registration system relies on self-attestation does not relieve election officials of their obligations under federal law when they are on actual notice of noncitizen voting. Nor can state procedures supersede federal criminal statutes.

Trump's post followed a week of escalating federal action. Earlier in the week, the DOJ mailed California election officials a USB drive containing voter roll citizenship data, then sent a separate letter with the password needed to open it. According to a report from The Hill, the state had 48 hours to compare 20,000 names that the Department of Homeland Security (DHS) identified as non-U.S. citizens against its own voter rolls.

On Thursday, the DOJ sued California. "If California was unable to independently confirm the citizenship of people on that list, the Federal Government asked that California set aside ballots received from them until the person's citizenship was confirmed," the lawsuit reads.

Under this approach, the state would hold the ballots in question until officials verified the voters' citizenship. The lawsuit does not ask California to discard the ballots outright.