A Washington, DC, federal judge has ruled against President Donald Trump in his fight to block House Democrats from getting his financial records, giving Democrats the first edge in their battle with the White House over congressional oversight.

On Monday, Judge Amit Mehta of the DC District Court decisively ruled in favor of the House Oversight Committee, whose chair, Elijah Cummings had subpoenaed 10 years’ worth of Trump’s financial records from accounting firm Mazars USA back in April.

“To be sure, there are limits on Congress’s investigative authority. But those limits do not substantially constrain Congress. So long as Congress investigates on a subject matter on which ‘legislation could be had,’ Congress acts as contemplated by Article I of the Constitution,” Mehta wrote. “Applying those principles here compels the conclusion that President Trump cannot block the subpoena to Mazars.”

Cummings moved to get those records following Michael Cohen’s congressional testimony, where Trump’s former personal lawyer claimed that Trump had misrepresented his net worth as a private citizen.

The president immediately tried to quash that subpoena in April, taking House Democrats to court and arguing the committee had overstepped its powers. White House lawyers argued Democrats didn’t have a legitimate legislative reason to pursue the information, and just wanted his financial records for political purposes.

But the judge sided with Democrats, saying that history — from the 1920s Teapot Dome Scandal to 1970s Watergate — has shown that congressional oversight into presidential misconduct can ultimately lead to legislative changes. Furthermore, Mehta wrote that years of past court decisions on Congress’s investigative power show “courts must presume Congress is acting in furtherance of its constitutional responsibility to legislate and must defer to congressional judgments about what Congress needs to carry out that purpose.”

The ruling was a clear-cut win for Democrats, but this is likely just the first round in the escalating fight for Trump’s financial records. And Mehta’s ruling is narrow, it just deals with the Mazars subpoena and doesn’t touch other battles over White House security clearances and Mueller-related testimony.

“Today’s decision is a resounding victory for the rule of law and our Constitutional system of checks and balances,” Cummings said in a statement. “Congress must have access to the information we need to do our job effectively and efficiently, and we urge the President to stop engaging in this unprecedented cover-up and start complying with the law.”

Trump is almost certain to appeal this ruling regarding his financial records, as he and his administration have made clear that he will resist any and all subpoena attempts by House Democrats.

Mehta’s ruling bolsters Democrats’ legal case in their larger subpoena battle with Trump

The Mehta ruling is narrow in that it only deals with the House Oversight Committee’s Mazars subpoena. But it’s a key development in the larger, ongoing subpoena battle between Trump and Congress, because it gives Democrats legal ammunition when they go to court to enforce other outstanding subpoena requests.

The Trump administration recently issued a blanket denial of all Democrats’ subpoena requests, saying the information they seek is politically motivated. Democrats, on the other hand, say the administration’s actions amount to an unprecedented attempt to block Congress from its constitutionally mandated oversight.

The Trump administration is sure to challenge Democrats in court at every turn; they will likely appeal Mehta’s ruling to prolong the case. But the speed with which the judge heard and decided the case is a huge win for congressional Democrats staring down many other subpoena fights with Trump, especially since these cases often wind up being a long, drawn-out process that can go on for years.

Of course, there is also fear from congressional committees that a judge could rule against them and give the executive branch more power to push back against future subpoenas. But the fact that Trump’s subpoena denial has been a blanket one has, if anything, emboldened Democrats. That’s because if Trump has said Democrat-controlled committees can’t get any information, it’s a much broader — and therefore harder to defend — argument than denying requests on certain grounds in specific cases.

“We have a very strong case,” Rep. Ted Lieu (D-CA), a member of the House Judiciary Committee, recently told Vox.

And it’s not just Democrats who think so. At least one former Justice Department official in the George W. Bush administration thinks Trump’s broad refusal could potentially hurt his legal argument.

“The thing that’s unusual is the blanket refusal,” John Yoo, the former deputy assistant US attorney general in the Bush DOJ’s Office of Legal Counsel, told the New York Times. “It would be extraordinary if the president actually were to try to stop all congressional testimony on subpoenaed issues. That would actually be unprecedented if it were a complete ban.”

Democrats have many more subpoena battles to fight with Trump, including one for the president’s tax returns, and another for the unredacted Mueller report. On each one, they have been slow and methodical, laying out a long paper trail before rushing into a court case.

Mehta’s new ruling proves it might have been worth it — they’ve built solid legal ground to stand on for future cases.