• The Philadelphia District Attorney's Office filed a lawsuit seeking to stop a political action committee controlled by billionaire Elon Musk from awarding $1 million to registered voters in swing states.
• The lawsuit by DA Larry Krasner comes days after the U.S. Department of Justice warned Musk's America PAC that its $1 million sweepstakes might violate federal election law.
• Musk is backing Republican nominee Donald Trump in the presidential election against Democratic nominee Kamala Harris.

The Philadelphia District Attorney's Office on Monday filed a lawsuit seeking to stop Elon Musk and his political action committee from awarding $1 million to registered voters in swing states, accusing them of "running an illegal lottery."

The lawsuit by DA Larry Krasner, which accuses Musk and his America PAC of trying to influence voters in the presidential election, comes days after the U.S. Department of Justice warned America PAC that its $1 million daily sweepstakes might violate federal election law.

Krasner's suit lawsuit names both the Tesla CEO Musk and America PAC as defendants.

Musk is backing Republican nominee Donald Trump in the presidential election against Democratic nominee Kamala Harris. CNBC has requested comment from Musk.

A court hearing on Krasner's application for a preliminary injunction against Musk and the PAC that would block them from continuing the daily award was set for Friday morning in Philadelphia.

"America PAC and Elon Musk are running an illegal lottery in Philadelphia (as well as throughout Pennsylvania)," the suit in the Philadelphia County Court of Common Pleas says.

The suit notes that at an Oct. 19 rally, Musk announced that if a registered voter turned over personal identifying information — address, cellphone and email address — and signed a petition pledging support for the Constitution, they would be eligible to be selected randomly for a $1 million prize.

"In other words, America PAC and Musk are lulling Philadelphia citizens – and others in the Commonwealth (and other swing states in the upcoming election) – to give up their personal identifying information and make a political pledge in exchange for the chance to win $1 million," the suit says.

"That is a lottery," the suit says. "And it is indisputably an unlawful lottery."

The suit says that under Pennsylvania law, all lotteries in that state must be regulated by the state.

Musk's lottery also violates Pennsylvania consumer protection law by "deploying deceptive, vague or misleading statements that create a likelihood of confusion or misunderstanding," the suit alleges.

Krasner in a statement Monday said, "The Philadelphia District Attorney is charged with protecting the public from public nuisances and unfair trade practices, including illegal lotteries."

"The DA is also charged with protecting the public from interference with the integrity of elections," Krasner said.

Later Monday, President Joe Biden was asked about the money giveaway by Musk's PAC.

"Tell him I'm registered, a million dollars," Biden quipped.

The president then said, "I think it's totally inappropriate."

Earlier this year, America PAC was briefly investigated by the North Carolina attorney general's office and the Michigan secretary of state's office after CNBC revealed it was collecting personal contact information of swing-state voters under the false pretense of helping them register to vote.

In response to the inquiries, the PAC told state officials it would fix several dead-end links on its site.

— Additional reporting by CNBC's Kevin Breuninger.