Justice Elena Kagan and Amy Coney Barrett raised the hypothetical of a potential presidential coup with Trump's attorney, who said that under their theory of immunity, ordering a coup could be considered an official act.

John Sauer maintained that impeachment and conviction are needed before a criminal prosecution in the hypothetical case of a coup raised by the justices.

And even then, Sauer said there would have to be a criminal statute expressly referencing the president, prompting an incredulous response from Barrett, who appeared to express a concern that Suer's argument was paradoxical.

"There would have to be a statute that made a clear statement that Congress purported to regulate the president's conduct," he said.

Justice Ketanji Brown Jackson said she was worried that granting Trump's position for presidential immunity would "embolden" a president to act criminally "with abandon."

"If someone with those kinds of powers, the most powerful person in the world, with the greatest amount of authority, could go into office knowing that there would be no potential penalty for committing crimes, I'm trying to understand what the disincentive is from turning the Oval Office into, you know, the seat of criminal activity in this country. ... I worry that we would have a worse problem than the problem of the president feeling constrained to following the law while he's in office," she said.

John Sauer responded by suggesting that history has shown that this hasn't happened so far. “I respectfully disagree with that because the regime you described is the regime we operated under for 234 years," he said.

As the questioning of Trump's attorney continues, Justice Elena Kagan noted that the framers of the Constitution consciously did not put in an explicit presidential immunity clause.

"They didn't provide immunity to the president," she told lawyer John Sauer. "And you know, not so surprising, they were reacting to a monarch who claimed to be against the law. Wasn't the whole point that the president was not a monarch and the president was not supposed to be above the law?"

In response, Sauer argued that the framers did put in an immunity clause "in a sense" with the executive vesting clause and that they adopted impeachment as a "structural check," which is a major part of Trump's defense against his federal charges.

"They did discuss and consider what would be the checks on the presidency and they did not say we would have criminal prosecution," Sauer said. "Everybody cried out against that as unconstitutional."

A notable response came from Chief Justice John Roberts when Trump's attorney pushed for the justices to remand the case back down to the lower courts to sort through which allegations in the indictment amount to an "official act" under the presidency versus those that were private and outside the office's authority -- and potentially criminally liable.

"The official stuff has to be expunged completely from the indictment before the case can go forward," John Sauer said.

"That's like a one-legged stool, right?" Roberts responded. "I mean, giving somebody money isn't bribery unless you get something in exchange. If what you get in exchange is to become the ambassador to a particular country, that is official, the appointment, it's within the president's prerogatives. The unofficial part is 'I'm going to get a million dollars for it.'"

In an unusual moment after this exchange, Justice Clarence Thomas raised unprompted whether Trump's legal team was challenging the legality of the appointment of special counsel Jack Smith -- a questionable theory previously pushed by right-wing lawyers like former Attorney General Ed Meese.

Sauer said Trump's legal team was making that argument in his separate Florida federal case, in which Trump is accused of mishandling classified information while out of office, but they weren't doing so directly in this case, to which Thomas did not follow up.

Justice Samuel Alito then asked Sauer if all official acts alleged in the indictment should be excluded from trial, to which Sauer answered they should.

But Justice Sonia Sotomayor pressed back on the notion of remanding the case, which outside observers see as one potential outcome that would likely draw out the lower court proceedings for many months, past the November election.

Sotomayor argued that even in the instances of acts that could be considered official, they came in the context of Trump pushing forward in his "private" intent of remaining in office despite losing to Joe Biden.

"I don't think the indictment is charging that the obstruction occurred solely because of conversations with the Justice Department," she said. "They're saying you look at all of the private acts and you look in the context of some of the public acts, and you can infer the intent, the private intent, from them."

Oral arguments have begun in Donald J. Trump v. United States.

Arguing for Trump is attorney D. John Sauer. Presenting for Smith is Michael R. Dreeben, who has argued more than 100 cases before the nation's high court.