During court arguments in October, the President's legal team said Mr. Trump cannot be investigated - even if he committed a murder on Fifth Avenue in Manhattan.
"I'm talking about while in office," Judge Denny Chin said during court arguments. "Nothing could be done - that is your position?"
"That is correct," the President's lawyer responded.
In this case, Manhattan prosecutors want documents from the Mazars accounting firm used by President Trump, as investigators want eight years of financial documents.
"The subpoena at issue is directed not to the President, but to his accountants," the judges wrote in their decision, as they said "compliance does not require the President to do anything at all."
But Mr. Trump's lawyers say a subpoena to his accounting firm is just the same as a subpoena to the President.
This case is part of a growing series of judicial fights involving the President over evidence about his tax returns, testimony by White House aides, and materials from the Mueller investigation into Russian interference in the 2016 elections.