President Donald Trump speaks to reporters in the Oval Office of the White House in Washington, September 16, 2019.

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 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.