Nearly two years after then-California Gov. Jerry Brown quashed a bill to force presidential candidates to release their tax returns, Golden State lawmakers have returned a nearly identical measure to the desk of Brown's successor.

Now California Gov. Gavin Newsom has less than two weeks to decide the fate of the proposed law, which has provoked fierce criticism from Republicans across the country.

"It was disappointing for a lot of people not to be able to have confidence that a major presidential candidate, and ultimately the president, didn't have financial conflicts of interest," California State Sen. Scott Wiener told CBS News. Wiener authored the bill with fellow state Sen. Mike McGuire.

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"I think it's time to require what everyone already thought was required," Wiener added.

Billed as the "Presidential Tax Transparency and Accountability Act," the law would demand that presidential candidates disclose five years of federal tax returns, in order to be listed on the state's primary election ballot.

As a candidate in 2017, Gavin Newsom supported the bill, prior to Brown's veto. The current measure on Newsom's desk today differs little from its predecessor, except that it expands the disclosure requirement to gubernatorial candidates.

"I was solicitous of amending it to include the governor. So, that's maybe suggestive of an inclination. But I haven't made the determination," the governor told reporters Friday.

The bill has revived a flood of Republican denunciations, condemning McGuire's and Wiener's measure as an unconstitutional gambit to extract the president's closely held tax returns.

"I urge Gov. Gavin Newsom to veto this unconstitutional bill, and I encourage Democrats in the Legislature to drop the political posturing and focus on addressing the myriad of problems truly impacting Californians," California Republican Party Chairwoman Jessica Patterson said in a statement.

"The Constitution is clear on the qualifications for someone to serve as president and states cannot add additional requirements on their own," Trump campaign communications director Tim Murtaugh told CBS News in a statement.

"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," Murtaugh added.

In the years since candidate Donald Trump first refused to disclose his tax returns, claiming they were "under audit," a flurry of efforts by states to force the release of the filings have sparked heated debate over such a measure's constitutionality.

McGuire dismissed arguments that his bill was unconstitutional as "hogwash."

"It's an easy soundbite to say it's unconstitutional. But this is bill is based off of data and fact, not soundbites. We believe that we will withstand any constitutional tests. And, candidly, I say bring it on," McGuire tells CBS News.

In 1994, the Supreme Court ruled that states — in that case, Arkansas — could not add on their own qualifications for congressional candidates.

Interpreting the high court's ruling six years later, the 9th U.S. Circuit Court of Appeals declared a California law unconstitutional for "creating an absolute bar to candidates, who otherwise meet the requirements of the Qualifications Clause."

Many expect judges would apply the same logic for the presidency. But courts have also upheld several so-called "ballot access" rules in primary elections, finding that states have a "right to regulate elections by imposing reasonable requirements on candidates."

"The Constitution prohibits states from adding additional 'qualifications' for ballot access, but no court has analyzed whether requiring tax return disclosure is a 'qualification,'" Abby Wood, an associate professor at the USC Gould School of Law, told CBS News in an email.

"The courts have upheld generally applicable, 'procedural' ballot access requirements, while striking down 'substantive' ones. It's easy to argue that this is a procedural requirement," wrote Wood.

Her conclusions in 2017 about the bill were among those cited in an analysis this year, by the California state senate's judiciary committee.

"Anyone who meets the other constitutional requirements to be president can also meet SB 27's requirements," the committee wrote in April.

Their analysis ultimately concluded there were "strong arguments" for the measure's constitutionality, but acknowledged "legitimate counterarguments."

"Perhaps the only thing that can be said with near certainty is that, if enacted, determining the constitutionality of SB 27 will wind up in the hands of the courts," the committee ultimately concluded.

"This is a very simple requirement," insists Wiener.

"Just like you have to fill out paperwork to get on the ballot, and collect signatures, or pay a fee. You need to disclose tax returns, and this isn't out of left field," the state senator explained.

Asked if they would challenge the proposed law in court, if signed by Newsom, both the Trump campaign and California's Republican party declined to comment. The Republican National Committee did not respond to a request for comment.

The bill comes amid House Democrats' court battle with the Trump administration, seeking to pry loose the president's unseen returns from the IRS. A bill signed into law by New York Gov. Andrew Cuomo this month could also open Trump's state tax filings there to Congress. That measure requires the state to cooperate with investigations by some U.S. congressional committees, under "certain circumstances."

State tax authorities can now share filings with congressional tax committees, including those of longtime New Yorker Donald Trump. But unlike the bill on Newsom's desk, such documents could remain unseen by the public. Those who have never filed taxes in the state would be unaffected.

It is unclear if President Trump would even need to appear on California's primary ballot. Even lacking the state's almost 200 delegates to the Republican convention, the president faces scant competition in securing his party's 2020 nomination.

Data from the National Conference of State Legislatures counts at least seven other states with similar pending bills. Only one — California's — is awaiting a governor's sign-off.

Across the aisle, the bill is unlikely to hinder many Democrats looking to compete in the Super Tuesday state. A number of them, most recently former Vice President Joe Biden, have already released some of their tax returns.

But beyond the bill's constitutional implications, Brown in his veto message also cited fears of the "slippery slope" such a law could unleash.

"Today we require tax returns, but what could be next? Five years of health records? A certified birth certificate? High school report cards? And will these requirements vary depending on which political party is in power? A qualified candidate's ability to appear on the ballot is fundamental to our democratic system," wrote Brown.

McGuire dismissed the former governor's "slippery slope" concerns as far-fetched.

"I believe Gov. Brown will go down as one of the most successful governors in California history. And Gov. Brown also did not have a history of releasing his tax returns," said McGuire.

"The current governor, Gov. Gavin Newsom, released his tax returns during the campaign. He did so because he put the interests of the state first," he added.