New York City Mayor Bill de Blasio on Thursday asserted that U.S. President Donald Trump would not get away with shooting someone on the city's Fifth Avenue a day after a Trump attorney argued to the contrary at a Manhattan court, citing presidential immunity.

"If anybody shoots someone they get arrested. I don't care if it's the President of the United States or anybody else," De Blassio told a press conference. "If you shoot someone, you should get arrested and we would arrest him," added the mayor who was until recently a candidate for the 2020 Democratic presidential nominee.

De Blasio was responding to the controversy triggered by the argument of Trump's lawyer at the 2nd U.S. Circuit Court of Appeals on Wednesday that a sitting president cannot legally be investigated or prosecuted for a criminal act while still in office, even if it involved a cold-blooded murder.

During the hearing at the federal court over whether the president can shield himself from a state grand jury subpoena seeking his tax returns, Judge Denny Chin asked what local authorities would do if Trump shot someone on Fifth Avenue, referring to a claim Trump made in January 2016 that he could shoot someone and not lose voters.

Attorney William Consovoy argued that New York authorities would have to wait until the president was out of office to arrest and charge him for that crime.

"Once a president is removed from office, any local authority" could prosecute him, the lawyer told the panel of three judges. "This is not a permanent immunity."

"Well, I'm talking about while in office. Nothing could be done? That's your position?" Judge Chin asked Consovoy, to which the attorney responded in affirmative: "That is correct. That is correct. Yes."

Mayor De Blasio retorted saying he disagreed. "Anyone calls themselves a lawyer who could say that should not be a lawyer, let's start with that," he said when asked at a press conference to respond to the controversial claim by Trump's lawyer.

"But if you shoot someone, that's a crime, and no one is above the law. He would be arrested. Period," he added.

The Manhattan District Attorney Cyrus Vance, also a Democrat, has subpoenaed eight years of Trump's tax returns from his accounting firm, Mazars USA, as part of a probe into hush money payments to two women in exchange for their silence about alleged affairs with the U.S. president.

Trump has denied the allegations while dubbing the investigation as "presidential harassment."

After Wednesday's hearing, the three-judge panel appeared inclined to reject the arguments that the president's tax returns can't be given to a New York grand jury due to his immunity from state criminal law.

Chief Judge Robert A. Katzmann told the lawyers at the conclusion of an hour-long arguments that the panel believed the attorneys "may be seeing each other again in Washington," hinting that the U.S. Supreme Court may have the last word on the case.