U.S. President Donald Trump sued California on Tuesday over a new law requiring presidential candidates to release their tax returns to run in the state's primary elections.
The lawsuit argues federal law does not allow states to impose their own qualifications for federal office.
It requires candidates running for USA president to release five years of their tax returns, which the state would publish for public viewing.
They say the law disenfranchises voters by denying them an opportunity to vote for their chosen candidate.
Both Trump and the RNC are filing suit against the law. They've filed a handful of lawsuits in federal courts across the country, mainly to stop House Democrats from seeking the tax returns through the Trump family and company's banks, an accounting firm or under a NY state law.
Trump refused to release his tax returns during the 2016 campaign, defying a practice followed by every presidential nominee for decades.
Citizens have had to pay federal income taxes since 1913, but it wasn't until 1973 when a USA president made his personal tax returns public. He said voters had already spoken about whether Trump should release his tax returns.
California is the first state to succeed in passing such a law, though others under Democratic control have tried.
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The Republican Party also filed a similar case on Tuesday.
The lawsuit specifically names California Secretary of State Alex Padilla and California Attorney General Xavier Becerra as defendants.
"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 signing the bill approved by the Legislature earlier this month. The other was filed last week by Roque "Rocky" De La Fuente, a California businessman who has run several low-profile campaigns for president.
A second lawsuit by the Trump campaign argues that states do not have the power to supplement qualifications for president set out by the US Constitution.
The Justice Department may reportedly take a position on whether Democrats can subpoena Trump's tax returns from when he was a private citizen.
The organization also argues that by limiting the law to primary elections, it does not apply to independent candidates.
"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". "The disclosure required by this bill will shed light on conflicts of interest, self-dealing, or influence from domestic and foreign business interest".