A federal judge in Manhattan had denied Trump's effort to block the subpoena.
A US appeals court on Friday backed a House of Representatives request for President Donald Trump's financial records including tax documents, rejecting an appeal by the president to block his accounting firm from handing over any information.
"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", Judge David Tatel wrote.
The House Oversight Committee had subpoenaed Trump's accounting firm, Mazars USA, for the documents, but the president's legal team argued that their investigation served no legislative objective.
Trump could appeal to the supreme court. The president's lawyers will undoubtedly fight the ruling, either before the full appeals court or by going directly to the Supreme Court.
A lower court rejected Team Trump's argument.
Dissenting was Judge Neomi Rao, a Trump appointee, who said the court was expanding Congress's powers to a new point they'd never been before. He was joined by Judge Patricia Millett, an appointee of former President Barack Obama.
In this case, let's start with the dissent. Trump's legal team has said that the investigation served no legitimate goal.
The committee, for its part, has said it is seeking the Trump financial statements, accounting records and other documents as part of its investigation into whether the president has undisclosed conflicts of interests, whether he has accurately reported his finances and whether he may have engaged in illegal conduct before and during his time in office.
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The White House, which has characterized congressional investigations into the president as "harassment", argued that Congress did not need the information to fulfill its role as legislator.
Perhaps anticipating future battles, Judge Rao pointed out that in the 1998 pursuit of impeachment against President Clinton, the full House had a floor vote to authorize an inquiry. Throughout our history, Congress, the President, and the courts have insisted upon maintaining the separation between the legislative and impeachment powers of the House and recognized the gravity and accountability that follow impeachment.
"What we have shown here is obviously a legitimate legislative goal", House general counsel, Douglas Letter, asserted during the same oral arguments.
Tatel also wrote that "we detect no inherent constitutional flaw in laws requiring Presidents to publicly disclose certain financial information". And that is enough.
"The Constitution and our historical practice draw a consistent line between the legislative and judicial powers of Congress". Eastland, 421 U.S.at 508. The House has made that point increasingly explicit even as it attempts to avoid making it formal.
Calls for Trump to release his tax returns began to surface long before he became president, with his Republican contenders calling on him to release the returns, as per a recent tradition which started under President Richard Nixon. "It does not seek to determine the President's fitness for office".
Of course, this is far from over. He could appeal to the Supreme Court.
On Thursday, Deutsche Bank told a United States appeals court that they did not have copies of Trump's tax returns.
Prediction: For Christmas, John Roberts will ask Santa a six-month supply of Pepcid and Excedrin.