A federal judge has sided with the Trump campaign's request to halt a California law that's aimed at forcing the president to release his tax returns.

U.S. District Judge Morrison England Jr. said Thursday that he'll issue a formal ruling by Oct. 1.

The ruling marks a major victory for President Donald Trump, who is fighting multiple Democratic-led efforts to force him to reveal the returns. California is expected to appeal.

The Trump campaign and Republican parties have sued over the law requiring candidates to release their tax returns to appear on the March 2020 primary ballot.

Democratic Gov. Gavin Newsom signed the law in July.

Lawyers for Trump and Republicans argue that it violates the U.S. Constitution by adding an additional requirement to run for president. They also said a federal law requiring presidents to disclose financial information supersedes state law.

"We are encouraged that the federal court tentatively concluded that a preliminary injunction should be granted," Trump's lawyer Jay Sekulow said in a statement. "We look forward to the court’s written order. It remains our position that the law is unconstitutional because states are not permitted to add additional requirements for candidates for president, and that the law violates the Constitution."