President Donald Trump could be left off the primary ballot in California next year if he does not release five years of his tax returns, because of a new law that Gov. Gavin Newsom signed Tuesday.

California is the first state to require presidential candidates to release their tax information, though lawmakers in at least 25 states have introduced similar legislation since Trump won the presidency. Although not required to do so, Trump was the first presidential candidate in more than 40 years not to release his taxes, and he has continued to refuse to reveal them as president.

The law is likely to face legal challenges. Newsom said his state is "well within its constitutional right," but critics of the tax-return disclosure effort say the Constitution sets out requirements to be president and states cannot add new ones.

Despite a flurry of bill introductions, few states are likely to follow California. Former California Gov. Jerry Brown vetoed similar legislation last year. He questioned whether the law was constitutional and expressed concern it could instigate a "slippery slope" for what states could require candidates to reveal.

Trump campaign spokesman Tim Murtaugh said there were "good reasons" Brown vetoed the measure.

"It's unconstitutional and it opens up the possibility for states to load up more requirements on candidates in future elections," Murtaugh said in an emailed statement. "What's next, five years of health records?"