(Reuters) - Elon Musk's $1 million giveaway for voters who sign his free-speech and gun-rights petition falls into a gray area of election law, and legal experts are divided about whether the billionaire supporter of Donald Trump could be running afoul of prohibitions on paying people to register to vote.

The Tesla CEO is promising to give $1 million each day to a randomly selected person who signs his online petition pledging to support the First and Second amendments of the U.S. Constitution, which protect the rights to free speech and gun ownership. The petition is only open to signatories who are registered voters in seven swing states likely to decide the presidential election.

"There is certainly an argument that this falls within the scope of a federal prohibition on paying a person to vote or register to vote," said Daniel Weiner of the left-leaning Brennan Center for Justice. "This is part of a pattern of him skating up to the edge of election laws that we've seen in the past several weeks." 

Musk's representatives did not immediately respond to requests for comment. 

Four legal experts 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.

Brad Smith, a Capital University Law School professor and former Federal Election Commission chairman, said Musk is likely in the clear because signing the petition is sufficiently far removed from registering to vote.

"The mere fact that there might be an incentive doesn't arise to a payment for a particular activity," Smith said.

The giveaway could be interpreted as Musk using his wealth to attempt to influence the tightly contested presidential race between Trump and his Democratic opponent, Vice President Kamala Harris. 

Musk's America PAC seeks to play a major role in helping mobilize and register voters in battleground states that could decide the election. 

Terms of the petition state that signers must be registered voters in Arizona, Georgia, Michigan, Nevada, North Carolina, Pennsylvania or Wisconsin - all states that are likely to decide the election.  

Pennsylvania's Democratic governor, Josh Shapiro, said on Sunday that the giveaway was "deeply concerning" and called on law enforcement to investigate. 

While Musk's promotion does not directly induce people to register, its timing and focus on battleground states indicate the petition component is merely a pretext, according to Richard Hasen, a law professor at the University of California, Los Angeles, who said the sweepstakes is therefore illegal. 

"I think signing the petition is irrelevant to the legal question because you must be a registered voter. It doesn't matter if you add other conditions," Hasen said, adding that the U.S. Department of Justice election crimes manual specifically cites lottery chances as potentially illegal payments. 

Adav Noti of the nonpartisan Campaign Legal Center agreed, saying it is illegal to give out money on the condition that people are registered to vote.

Weiner of the Brennan Center said the promotion is legally "fishy" but falls into a gray area. The question boils down to whether signing the petition is merely a pretext for getting people to register to vote, he said.

But Smith of Capital University said Musk has other plausible reasons for wanting people to sign the petition, including gathering names of likely voters who support his causes.

Musk, ranked by Forbes as the world's richest person, has so far given at least $75 million to America PAC, according to federal disclosures, making the group a crucial part of Trump's bid to regain the White House.

The entrepreneur has increasingly supported Republican causes and this year became an outspoken Trump supporter.

Trump in turn has said that if elected, he would appoint Musk to head a government efficiency commission.

Asked by reporters about Musk's giveaway on Sunday, Trump said, "I haven't followed that."