Musk gave out an eighth check on Saturday in Pennsylvania.
PHILADELPHIA -- The Philadelphia district attorney sued Elon Musk and his super PAC on Monday over the billionaire's controversial $1 million registered voter giveaway.
The lawsuit from Philadelphia District Attorney Larry Krasner claims Musk and his America PAC are "running an illegal lottery in Philadelphia (as well as throughout Pennsylvania)."
Musk announced the eighth winner of his super PAC's $1 million prize in Lancaster, Pennsylvania, on Saturday and doubled down on his promise to continue offering the money to a registered swing state voter who has signed his petition. He said participants are not required to vote, but the online petition form says one has to be a registered voter to be eligible.
"We're trying to get attention for this very important petition to support the Constitution. And, it's like, if we, you know -- we need the right to free speech; we need the right to bear arms," Musk said at the rally.
"So we're going to be giving out a million dollars every day through Nov. 5," he continued. "And also, all you have to do is sign the petition in support of the First and Second Amendments. That's it. You don't even have to vote. It'd be nice if you voted, but you don't have to. And then just basically sign something you already believe in, and you get a test to win a million dollars every day from now through the election."
Federal law singles out anyone who "pays or offers to pay or accepts payment either for registration to vote or for voting." The penalty is a fine of no more than $10,000 or a prison sentence as long as 5 years.
When asked for comment, a representative for America PAC pointed ABC News to a post on X announcing Monday's $1 million giveaway winner, which was published after news of the lawsuit broke. The winner on Monday was from Michigan, according to the post.
The person added it is fair to "infer" the PAC plans to continue handing out the $1 million checks.
The Department of Justice sent a letter to Musk last week warning him the giveaway may violate federal law, a source familiar with the matter confirmed to ABC News. The letter from the Election Crimes Branch of the DOJ's Public Integrity Section was sent to Musk's PAC, the source said.
Several experts ABC News spoke to in the wake of Musk announcing the giveaway said it occupies a blurry area of law.
"I've gone back and forth on it," Richard Briffault, a professor of legislation at Columbia University Law School, told ABC News. "It clearly violates the spirit of the statute, but it's not 100% clear to me that it violates the letter of the law."
Other experts, like Doug Spencer, a professor of election law at the University of Colorado, said "it seems like it really crosses the line."
ABC News' Max Zahn contributed to this report.