The personal information of a sitting president of the United States cannot be secured through a state grand jury subpoena, lawyers for President Donald Trump told a panel of judges in an argument before the U.S. Court of Appeals for the Second Circuit Tuesday.

Pressing his argument, William Consovoy of Consovoy McCarthy took the position that Trump has immunity from all local criminal proceedings while in office.

All sides in the matter have voiced their understanding that the U.S. Supreme Court would have the final say on Trump's bid to block Manhattan District Attorney Cyrus Vance Jr. from enforcing a subpoena on the president's personal accountants seeking, among other things, eight years of tax returns.

Chief Judge Robert Katzmann said from the bench that he knows the case will go to the U.S. Supreme Court. And Vance agreed last week to stay enforcement of the subpoena if Trump seeks certiorari at the Supreme Court, as long as he asks the court to hear the appeal in its current term.

Members of the panel—composed of Katzmann, Senior Judge Christopher Droney and Judge Denny Chin—said they would proceed "deliberately" in considering the case.

At one point, Chin asked Consovoy the "Fifth Avenue question," based on Trump's campaign rally quip that he could shoot someone in midtown Manhattan and he wouldn't lose any voters.

Consovoy said if such an event actually happened, the New York City Police Department could not arrest the president. He added, however, that police could act once the president has left office.

Carey Dunne, general counsel to the DA's office, told the judges that tax returns are not specially privileged in the context of a criminal investigation, even though both tax authorities and grand juries are obligated to keep them secret.

"They're making this up, Your Honor, that's all I can say," he said.

Consovoy reiterated that the case is not about tax returns but about immunity.

He has also pressed concerns about the secrecy of grand jury proceedings against Trump, often questioning whether a Manhattan grand jury might disclose Trump's tax returns.

At the argument, panel members asked Dunne to address that issue. 

The DA's office is committed to ensuring confidentiality, Dunne said. Even if Congress asks to see the grand jury materials, he said, the DA's office would not be at liberty to reveal them.

Consovoy again noted his concern Wednesday about similarities between the subpoena at issue in this case and a subpoena sent to Trump's accounting firm, Mazars USA, from the U.S. House of Representatives. Dunne said the DA's office chose to use a similar subpoena as a matter of convenience for Mazars.

The subpoena mentioned subjects outside Manhattan, including the Trump International Hotel in Washington, D.C., Dunne acknowledged, but he said Manhattan investigators routinely examine the "tentacles" of financial matters based in the city and extending outside it.

Trump appealed the case to the Second Circuit after U.S. Senior District Judge Victor Marrero dismissed the case in the Southern District of New York.

Marrero ruled that federal courts lack jurisdiction in this situation, but writing in the alternative, he found that Trump would not be harmed by the grand jury subpoena.

Droney asked Dunne what would happen logistically if the DA's office is allowed to enforce its subpoena while the president is still in office, if a sitting president cannot be indicted.

Dunne said that's when the DA's office believes Trump's immunity claims would be ripe for consideration. They would have time to claim immunity because the DA's office routinely notifies potential defendants when grand jury proceedings are coming to an end, to give them a chance to testify, Dunne said.

Katzmann asked whether federal courts should still abstain, in Dunne's view, in the event of a dispute over Trump's immunity from indictment. Dunne said they should abstain, but Katzmann appeared skeptical.

"Comity washes away when there is inherent state-federal conflict," Katzmann said.

A sitting president's vulnerability to criminal indictment after a shooting is a different question than the one facing the Second Circuit, constitutional law professor David Rudenstine of the Cardozo School of Law said. 

Trump's argument is actually more extreme, in Rudenstine's view, because he's seeking to block an investigation that may include people or businesses other than himself.

Along similar lines, Rudenstine said, Trump goes farther in his argument than then-President Richard Nixon did when he was trying to avoid a subpoena for audiotapes recorded in the Oval Office. Nixon was eventually labeled an unindicted co-conspirator; Rudenstine said Trump is trying to shut down a fairly broad investigation long before it could reach any outcome like that.

"The president [is saying] 'No criminal investigation that could touch on the president is permitted,'" Rudenstine characterized Trump's argument.

Vance had no comment on the matter after the argument.

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