President Trump would be barred from appearing on California’s primary ballot next year if he declines to disclose his tax returns under a measure signed into law Tuesday by Gov. Gavin Newsom (D) that could prompt other Democratic-led states to follow suit.

The new law is expected to draw a high-profile court challenge, but its implications for Trump remain unclear. Absent the emergence of a credible Republican primary challenger, he could opt not to appear on California’s ballot and still win the GOP nomination.

Trump broke with decades of tradition during the 2016 election by not voluntarily releasing his tax returns. His administration has rebuffed efforts by the Democratic-led House to obtain the documents from the Internal Revenue Service.

In a statement, Newsom said that given its size, California has “a special responsibility to require this information of presidential and gubernatorial candidates.”

Rep. Bill Pascrell Jr. (D-N.J.) on May 17 slammed Treasury Secretary Steven Mnuchin for refusing to give President Trump's tax returns to Congress. (JM Rieger/The Washington Post)

“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 said.

Jay Sekulow, Trump’s personal attorney, said in a statement that California’s “attempt to circumvent the Constitution will be answered in court.”

Tim Murtaugh, a Trump campaign spokesman, said that California had run afoul of the Constitution by passing the measure, which was approved by the legislature along party lines.

“The Constitution is clear on the qualifications for someone to serve as president and states cannot add additional requirements on their own,” Murtaugh said 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.”

Though inspired by Trump, the law applies to any candidate seeking the presidency or the governorship of California.

Candidates are required to file copies with the California secretary of state of every tax return filed with the IRS in the five most recent taxable years. Filings are required at least 98 days ahead of the primary election.

California’s primaries are scheduled for March 3, the day known as Super Tuesday because of the large number of delegates at stake.

House Ways and Means Committee Chairman Richard E. Neal (D-Mass.) has requested six years of Trump’s personal and business tax returns, from 2013 to 2018, a period that includes several years before Trump became president.

Neal recently sued the Trump administration in federal court to obtain the records, after Treasury Secretary Steven Mnuchin argued in a May letter that Neal’s “unprecedented request” should be denied.

Neal cited a 1924 law that gives his committee the power to request tax returns from the Treasury Department for review in closed session.

Carol D. Leonnig contributed to this report.