District Attorney Larry Krasner had filed suit last month to try to have the sweepstakes shut down under Pennsylvania law.
"Although (Krasner) alleges that America PAC and Elon Musk 'scammed' people," Common Pleas Court Judge Angelo Foglietta wrote in the opinion Tuesday, "DA Krasner failed to provide any evidence of misuse beyond mere speculation."
The prize was open only to swing state voters who signed a petition endorsing the constitutional right to free speech and to bear arms. Lawyers for the PAC revealed in court on Nov. 4 that the recipients did not win a game of chance, but were instead chosen to be paid spokespeople for the group.
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Musk, who committed more than $70 million to the political action committee to help Donald Trump return to the White House and other Republicans win, has now been tapped to help lead a government efficiency effort.
Krasner argued that the more than 1 million people who registered were "scammed for their information." Musk's lawyers, defending the effort, called it "core political speech."
Foglietta had denied Krasner's petition after last week's hearing, but only explained his reasoning in the opinion. He said he did not want to issue a "superfluous" order, given that there was only one sweepstakes remaining by then - and Musk's lawyers had said the last person chosen would not be from Pennsylvania.
"We respectfully disagree with the judge's opinion," Krasner said Wednesday in a statement.
Musk is the CEO and largest shareholder of Tesla. He also owns the social media platform X and the rocket ship maker SpaceX.