California enacted a law this week that requires presidential candidates to submit five years of income-tax filings to be eligible for the state's primary ballot, the Los Angeles Times reported.

The law's passage comes amid President Donald Trump's years-long refusal to release his own tax returns because he claims they're under audit.

The law will likely be hotly-contested in the courts as Trump's defenders say the law violates his First Amendment right of association.

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A new California law that took effect Tuesday requires presidential candidates to submit five years of income-tax filings in order to be eligible for the primary ballot in the state, the Los Angeles Times reported.

According to the law, presidential candidates must release their tax returns by late November if they want a spot on the primary ballot in March.

The law's passage comes amid President Donald Trump's years-long refusal to release his own tax returns because he claims they're under audit. (The Internal Revenue Service has no rule barring an individual from releasing their returns if they're under audit.) Trump has given no indication that he will release his taxes ahead of next year's election.

California's law does not bar a candidate who refuses to release their taxes from being eligible for the statewide ballot in the November 2020 presidential election, according to the Times.

California Gov. Gavin Newsom signed the bill into law after it passed the state's Democratic-controlled legislature in a party-line vote.

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"As one of the largest economies in the world and home to one in nine Americans eligible to vote, California has a special responsibility to require this information of presidential and gubernatorial candidates," Newsom said in a statement after he signed the bill earlier this month.

"These are extraordinary times and states have a legal and moral duty to do everything in their power to ensure leaders seeking the highest offices meet minimal standards, and to restore public confidence," he added. "The disclosure required by this bill will shed light on conflicts of interest, self-dealing, or influence from domestic and foreign business interest."

Meanwhile, the president's defenders say the law violates his First Amendment right of association.

"The Constitution is clear on the qualifications for someone to serve as president and states cannot add additional requirements on their own," said Tim Murtaugh, the Trump reelection campaign's communications director, told the Times. "The bill also violates the 1st Amendment right of association, since California can't tell political parties which candidates their members can or cannot vote for in a primary election."

The passage of California's new law comes as the president weathers a flurry of investigations led by congressional Democrats.

In addition to suing to obtain Trump's federal tax returns, Democratic lawmakers are also seeking information related to Trump's business dealings, accounting statements, grand-jury information contained in the former special counsel Robert Mueller's final report in the Russia investigation, and more.