A judge ordered all parties, including Elon Musk, to attend a court hearing in Philadelphia on Thursday in a lawsuit seeking to stop a political action committee controlled by the billionaire from awarding $1 million to registered U.S. voters in battleground states ahead of the Nov. 5 U.S. election.

The Philadelphia District Attorney's Office filed the lawsuit on Monday. It called the giveaway by Musk's America PAC, which backs Republican former President Donald Trump, an "illegal lottery" that enticed Pennsylvania residents to share personal data.

"It is further ordered that all parties must be present at the time of the hearing," a judge wrote on Wednesday in an order with the Philadelphia County Court of Common Pleas. The hearing in the case was moved up to Thursday morning from Friday.

Trump faces Democratic Vice President Kamala Harris in what polls show to be a tight race for the White House.

A representative for America PAC did not immediately respond to a request for comment. Musk's representatives have not responded to requests for comment.

Musk promised to give $1 million each day to someone who signed his online free-speech and gun-rights petition. Legal experts consulted by Reuters last week were divided on whether the giveaway violates federal laws that make it a crime to pay or offer to pay a person to register to vote.

The Justice Department sent a letter to America PAC warning that the billionaire's giveaways for registered voters who sign his petition may violate federal law, CNN reported last week.

The Trump campaign is broadly reliant on outside groups for canvassing voters, meaning the super PAC founded by Musk - the world's richest man - plays an outsized role in what is expected to be a razor-thin election.