Elon Musk says he will give away $US1 million ($1.4 million) a day from now until next month's US election, with the cash to go to people who sign his online petition in support of the first and second amendments in the US Constitution.
Those amendments protect American citizens' right to freedom of speech and to bear arms legally.
The Tesla and SpaceX co-founder gave away the first million-dollar cheque on Saturday to an attendee of his America PAC event in Pennsylvania, aimed at rallying supporters behind presidential candidate Donald Trump, in a move that has raised questions over the legality of the payments.
Attendees of an event hosted by Mr Musk on Saturday had to sign the petition, allowing America PAC to gather their contact details for more potential voters that it can work to get to the polls for Trump.
The man announced as the first winner was John Dreher, who Mr Musk says was unaware he was going to be given the payout.
Mr Musk's America PAC organisation uses participants' details to try and influence Americans to register to vote. (Reuters: Rachel Wisniewski)
The billionaire created America PAC as a political action organisation in support of Trump's presidential campaign to help mobilise and register voters in battleground states.
Election law experts have now voiced concerns that Mr Musk could be breaching federal laws that ban the payment of cash to people with the intention of getting them to register to vote or to vote in a particular way.
The laws cover not only cash payments, but also anything of monetary value like liquor or lottery chances, according to a US Justice Department election-crimes manual.
Mr Musk has become a vocal supporter of former US president Donald Trump in his bid to be re-elected. (Reuters: Carlos Barria)
Rick Hasen, a political science professor with UCLA's Law School, says Mr Musk would not be breaking any laws if he were only offering money for people to sign his petition.
"The problem is that the only people eligible to participate in this giveaway are the people who are registered to vote. And that makes it illegal," Professor Hasen said.
Mr Musk has been ranked by Forbes as the world's richest person and has already contributed at least $US75 million to America PAC, according to federal disclosures, making the group a crucial part of Trump's bid to regain the White House.
ABC/wires