The House Oversight Committee issued the subpoena back in April; GOP lawmakers denounced the move at the time as 'an astonishing abuse' of Congressional authority.
But twice now, the courts have found otherwise.
In a scathing dissent, Judge Naomi Rao argued the only legitimate way for Congress to get access to the President's financial records would be through impeachment.
"The House may not use its legislative power to circumvent the protects and accountability that accompany the impeachment power," Rao wrote.
"Allowing the Committee to issue this subpoena for legislative purposes would turn Congress into a roving inquisition over a co-equal branch of government," added Rao, who was put on the D.C. Circuit Court of Appeals by Mr. Trump.
The two other judges involved in the decision were put on the appeals court by President Clinton (Tatel) and President Obama (Millett).
The President still has the option of appealing this decision - either to the full D.C. Court of Appeals, or directly to the U.S. Supreme Court.