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 $1m to registered US voters in battleground states before the 5 November election.

The Philadelphia district attorney’s office filed the lawsuit on Monday. It called the giveaway by Musk’s America Pac, which backs Donald Trump, an “illegal lottery” that entices 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 county court of common pleas. The hearing in the case was moved up to Thursday morning from Friday.

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 has promised to give $1m each day to someone who signs 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.

Before an extremely tight presidential race between Trump and Kamala Harris, Pennsylvania is seen as a crucial swing state that could determine the outcome of the election. “Pennsylvania will be a decisive Republican victory,” Musk tweeted on Wednesday.

Josh Shapiro, Pennsylvania’s Democratic governor, said earlier this month that he thought law enforcement should look into the legality of the giveaway.

“I think there are real questions with how he is spending money in this race, how the dark money is flowing, not just into Pennsylvania, but apparently now into the pockets of Pennsylvanians,” Shapiro told NBC’s Meet the Press on 20 October. “That is deeply concerning.”

At a Musk town hall in Pittsburgh on 20 October, at which the Tesla CEO praised Trump and gave a giant $1m check to a woman in a red Trump T-shirt, audience members appeared unfazed by the criticism of the scheme, and said they admired Musk’s success as a businessman, and what they saw as his championing of free speech.

“I fear if Trump does not win, we are going to have a single-party state that is going to be like California, but actually worse,” Musk told the audience.

Musk has shared photographs of voters with $1m checks on X, the social media platform he owns. On Wednesday, the America Pac account announced that “Joshua from North Carolina earned $1M after signing our petition in support of the Constitution”.

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.