Speaker Nancy Pelosi Nancy PelosiDemocratic senator to party: 'A little message discipline wouldn't kill us' Overnight Health Care: New wave of COVID-19 cases builds in US | Florida to lift all coronavirus restrictions on restaurants, bars | Trump stirs questions with 0 drug coupon plan Overnight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds MORE (D-Calif.) on Friday praised an appeals court ruling that could pave the way for House Democrats to obtain some of President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE's financial records, saying it shows “increased outside validation of our efforts to hold the President accountable.”

A panel of judges for the federal appeals court for the D.C. Circuit ruled Friday that a House Oversight and Reform Committee subpoena issued in April to Trump's accounting firm, Mazars USA, is "valid and enforceable." Trump had attempted to quash the subpoena.

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“This morning, we won a major victory in the D.C. Circuit in the Mazars case," Pelosi wrote in a Dear Colleague letter to members of her caucus. "The Court rejected the Administration’s defiance of Congress’s oversight authority, writing in the majority opinion that ‘Contrary to the President’s arguments, the Committee possesses authority under both the House Rules and the Constitution to issue the subpoena, and Mazars must comply.’”

Jay Sekulow Jay Alan SekulowNow, we need the election monitors Judge denies Trump's request for a stay on subpoena for tax records Judge throws out Trump effort to block subpoena for tax returns MORE, a personal lawyer for Trump, said in a statement that the president's team is "reviewing the opinion and evaluating all options including appeals."

Democrats' subpoena in the Mazars case does not explicitly seek Trump's tax returns. They are seeking those documents in a separate lawsuit.

Pelosi has been one of the biggest proponents of using the courts to bolster congressional oversight of Trump, his administration and his businesses. Democrats now hope their impeachment inquiry will provide them greater leverage in the courts.

In Friday's letter, Pelosi blasted the White House’s announcement earlier this week that it would not cooperate with the House inquiry.

“'The president’s refusal to cooperate in confirming (or disputing) the facts already on the public record should not delay or frustrate the House’s performance of its constitutional duty,'” she wrote, quoting a letter from 17 former Watergate prosecutors.

“This week, we have seen increased outside validation of our efforts to hold the President accountable and these statements speak to the heart of the Constitutional challenge that we face," she added.

--Updated at 2:06 p.m.