Trump lawyers contended in a 20-page letter to Mueller in January, before Giuliani joined the president's legal team, that he cannot be compelled to testify through a subpoena and argued he could not have obstructed justice by firing FBI director James Comey when he was leading the Russian Federation investigation because as president he has unlimited power to terminate the investigation.
The letter is dated January 29 and addressed to Mueller from John Dowd, a Trump lawyer who has since resigned from the legal team. "So bad for our country".
This latter theory was something touched on in the newly leaked letter. "Should be looking at Dems corruption instead?"
"I don't believe that would be a legal question", McCarthy responded.
Citing the powers given to him by the Constitution, it says the president can "terminate the inquiry, or even exercise his power to pardon".
Trump in recent days has contended that the Federal Bureau of Investigation planted a "spy" in his campaign, although there is no evidence that the investigative agency embedded anyone in the Trump operations ahead of the November 2016 vote.
Mueller took over an existing FBI counterintelligence investigation a year ago. The president expressed dismay that, when still a candidate, he wasn't told that authorities were probing Paul Manafort, who was hired as Trump's campaign chairman.
Trump's lawyers argued in a letter to the special counsel that the president could not have obstructed the probe given the powers granted to him by the Constitution, the New York Times reported on Saturday.
Pedro Sánchez, new Spanish prime minister, as no-confidence motion triumphs
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The only time the privilege concept has been tested in court about a sitting president also involved materials rather than testimony. "Thus, full cooperation was in order, and was in fact provided by all relevant parties".
If Trump does not consent to an interview, Mueller will have to decide whether to go forward with a historic grand jury subpoena.
Both Mr Trump and Russian Federation have continued to deny any collusion in the run-up to his shock election triumph, with the U.S. leader previously labelling the investigation a "witch hunt".
It is unclear, too, whether and to what extent Mueller might be able to compel Trump to testify, if the president will not agree to a voluntary interview.
Critics accused Mr Trump of subverting the rule of law. Dowd has since left Trump's legal team, replaced by Giuliani.
On NBC, the former mayor of NY said.
"Trump's lawyers' sweepingly Nixonian claim of unbounded presidential power is inconsistent with the core American principle that no-one is above the law", Tribe wrote on Twitter.
Trump has stated that Comey was sacked for his incompetence in handling the Clinton email investigation.
The principle laid out in the letter is "a ludicrous legal theory", said Neal Katyal, a former acting solicitor general who now works in private practice at Hogan Lovells. "Pardoning other people is one thing, pardoning yourself would be tough". "[Comey is] the wrong man for that position".
"We are prepared to meet to discuss a final list of questions that you need to be answered so that the Nation may move forward, and so that we may preserve the dignity of the Office of the President of the United States", the letter states.