In a ruling Monday morning, the U.S. Court of Appeals for the Second Circuit denied President Donald Trump's request for a preliminary injunction protecting him from a grand jury subpoena for his tax returns.

The court in an opinion written by Chief Judge Robert Katzmann rejected the notion that the president is immune from all state criminal processes.

"After reviewing historical and legal precedent, we conclude only that presidential immunity does not bar the enforcement of a state grand jury subpoena directing a third party to produce non‐privileged material, even when the subject matter under investigation pertains to the president," Katzmann wrote.

He also said that there is no claim of executive privilege in the tax documents sought from Mazars USA. Nor do they bear any relationship to the president's official functions.

Katzmann was joined in the opinion by Circuit Judges Denny Chin and Christopher Droney.

The panel was careful to avoid making a statement on whether presidents can be prosecuted while in office, but they wrote that prohibiting states from "even investigating potential crimes committed by him for potential later prosecution" would "exact a heavy toll on our criminal justice system."

The court vacated a ruling from U.S. District Judge Victor Marrero of the Southern District of New York that dismissed Trump's complaint on federal jurisdictional ground. That decision was based on the abstention doctrine articulated in the 1971 U.S. Supreme Court case Younger v. Harris. That doctrine says federal court should stand down from ruling on civil matters related to an ongoing criminal matter.

The Second Circuit however agreed with the district court's finding that presidential immunity does not extend to grand jury subpoenas aimed at third parties.

Trump sued Manhattan District Attorney Cyrus Vance Jr. in September over a subpoena delivered to Trump's accounting firm, Mazars, for eight years of his tax returns.

The Second Circuit judges stressed that their ruling is not a blanket determination of the extent of presidential immunity.

"We have no occasion to decide today the precise contours and limitations of presidential immunity from prosecution, and we express no opinion on the applicability of any such immunity under circumstances not presented here," the judges wrote.

Vance and Trump's legal teams previously agreed that the DA's office will not enforce the subpoena until 10 calendar days after the Second Circuit issues its opinion. The Second Circuit judges acknowledged during oral arguments that their ruling is sure to be appealed to the U.S. Supreme Court.

Any petition for certiorari must be filed during the 10-day time period, the lawyers agreed before arguments, and Trump must request that the Supreme Court hear the case in the current term.

The case was remanded to the U.S. District Court for the Southern District of New York.

Marrero, in his decision on Trump's motion for an injunction, criticized the president's legal team's heavy reliance on memos from the U.S. Department of Justice's Office of Legal Counsel, noting that the memos do not carry the same legal weight as court opinions.

The Second Circuit judges found it unnecessary to consider whether the memos are persuasive, they wrote, because they dealt "almost exclusively" with whether presidents can be indicted—not whether they can be investigated.

A subpoena is a "perfectly ordinary way of gathering evidence," Katzmann wrote, adding that in contrast to some cases cited by the Justice Department in its amicus brief for this case, Trump's tax returns are not protected by executive privilege.

The panel made reference to the 1974 U.S. Supreme Court case United States v. Nixon, in which the president asked for protection of tapes of executive discussions. Katzmann wrote that case demonstrated that investigators must demonstrate specific need to overcome executive privilege claims. But the doctrine, he concluded, has no application when it is personal and not official documents that are the subject of law enforcement interest.

"Surely the exposure of potentially sensitive communications related to the functioning of the government is of greater constitutional concern than information relating solely to the president in his private capacity and disconnected from the discharge of his constitutional obligations," Katzmann wrote.

A spokesman for Vance's office declined to comment.

READ the Second Circuit's ruling here:

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