California governor Gavin Newsom has signed a law into immediate effect that would require President Trump to disclose his tax returns in order to appear on the California Republican primary ballot.

The law, which was approved by the legislature along party lines earlier this month, requires all presidential and gubernatorial candidates to disclose the past five years’ worth of tax returns in order to appear on a primary ballot.

“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. “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.”

The law is likely to be challenged in the courts. The communications director for the president’s reelection campaign released a statement to the Los Angeles Times asserting that the new law violates the first amendment right of association and infringes on the Constitution’s power to delineate the requirements for presidential candidates.

According to the Times, the new law does not appear to prevent any candidate that does not disclose their tax returns from appearing on the 2020 general election ballot in California.