Before the Senate debates a bill to protect Special Counsel Robert Mueller from being fired by President Trump, it should consider this: Mueller’s use of a subpoena to require testimony by the president would violate the separation of powers in the Constitution and is an abuse of the grand jury process.

In addition, Mueller’s proposed questions for President Trump in the special counsel’s wide-ranging investigation of Russian interference in the 2016 presidential election would violate Article II of the Constitution and executive privilege.

Here’s a simple fact that Mueller chooses to ignore: A sitting president cannot be indicted. This fact cuts the legs out from under Mueller’s efforts to require testimony by President Trump.

In the wake of Watergate, a Republican Justice Department Office of Legal Counsel (OLC) in 1973 thoroughly discussed whether a president could be subject to criminal prosecution. Because the president is “selected in a highly complex nationwide effort,” the OLC found it would be “incongruous” to “bring him down … by a jury of twelve, selected by chance ‘off the street.’”

Action by the House and Senate, via impeachment, is the appropriate process for “such a crucial task, made unavoidably political by the nature of the ‘defendant,’” the OLC said.

The OLC observed that the “modern Presidency” has had to “assume a leadership role undreamed of” in earlier years. It added: “The spectacle of an indicted President still trying to serve as Chief Executive boggles the imagination.”

In 2000, because of three U.S. Supreme Court cases, a Democratic Justice Department OLC revisited the issue of presidential immunity from criminal prosecution.

Two cases concerned President Richard Nixon, the most well-known involving the “Nixon tapes.” After indicting Nixon aides, the special prosecutor in the case subpoenaed the Nixon tapes (recordings of the president’s conversations with his aides) for evidence at trial. The Supreme Court upheld the subpoena with specific limitations requiring in camera review (a legal term meaning privately, not in open court) and said only relevant and material information needed to be produced.

The other Nixon case held that the president was immune from civil liability for “official acts.”

In the third case, involving Paula Jones (who claimed Bill Clinton sexually harassed her), the Supreme Court held that Clinton was not immune from civil liability involving matters occurring before he took office, since such matters were not official presidential acts. (Independent Counsel Ken Starr withdrew his subpoena when President Clinton agreed to testify, so that case was not discussed.)

The OLC determined that none of the Supreme Court’s rulings altered the 1973 opinion finding the president “uniquely immune” from criminal process.

In dealing with the Nixon tapes, the high court balanced the president’s “generalized interest in confidentiality” with the requirement of “the fair administration” of a criminal trial. Thus, the ruling had no bearing on whether a president could be indicted. The other two cases were civil.

The OLC noted that criminal prosecutions are different from civil litigation, requiring personal attention and imposing “physical disabilities.” Therefore, “criminal proceedings against a President in office should not go beyond a point where they could result in so serious a physical interference with the President’s performance of his official duties that it would amount to an incapacitation.”

If Mueller cannot indict President Trump, what possible use can he make of any presidential testimony? The only option is that he will provide it to Congress for consideration of articles of impeachment.

But referring President Trump’s testimony to Congress would abuse the grand jury process, which is only to be used for a criminal proceeding. According to the U.S. Attorneys’ Manual, which Special Counsel Mueller is obligated to follow: “A grand jury has but two functions – to indict or, in the alternative, to return a no bill.”

Providing the legislature with testimony obtained from an executive branch grand jury subpoena also violates the Constitution’s separation of powers.

Mueller reports to Deputy Attorney General Rod Rosenstein, an executive branch official. Impeachment is purely a legislative function. The executive cannot utilize its awesome power to compel grand jury testimony for the purpose of providing it to another governmental branch.

If Congress finds the president’s refusal to testify an impeachable offense, it can allege so in articles of impeachment.

The substance of the recently leaked list of questions that Special Counsel Mueller outlined for President Trump’s counsel is also in violation of the Constitution and executive privilege. Not one of the questions passes requirements mandated by the Constitution and case law defining executive privilege.

Any question about firing FBI Director James Comey or obtaining National Security Adviser Michael Flynn’s resignation violates the president’s Article II authority to have vested in him “all executive power.”

The president had unfettered authority to fire both officials for any reason, for multiple reasons, or for no reason. Incidentally, if the firing of Comey can be construed as obstruction of justice, then Rosenstein – who discussed such a firing with the president and wrote a scathing memo recommending that Comey be fired – is a co-conspirator. Yet, he is supervising the Mueller investigation.

Numerous questions deal with the deliberative process, such as how were the decisions made to request the resignation of Flynn and to fire Comey. Some request information about the president’s discussions with White House Counsel Don McGahn.

The answers to these questions all involve the decision-making process and, as such, are clearly covered by executive privilege.

The president is not readily available to be interviewed under established case law. There must be a “demonstrated, specific need for evidence in a pending criminal trial,” which courts have defined as evidence that is material to the matter at issue and not available elsewhere with due diligence.

Ignoring the obvious – that there is no criminal trial pending as in the Nixon tapes case – not one Mueller question can meet the standard that would require executive privilege to be waived.

Unless, of course, you count the numerous questions asking what the president “thought” in response to various situations. These include Comey’s Jan. 6, 2017 briefing to President-elect Trump; Comey’s March 20, 2017 testimony before the House Intelligence Committee; the appointment of a special counsel and other issues.

It is correct that only the president can state what he “thought” of the listed occasions. Yet, I recall the Catholic confessional as the only place where I have been penalized three Hail Marys after admitting to sinful thoughts. A president’s thoughts are not – and cannot be – the basis for any governmental inquiry.

Mueller has over a dozen experienced lawyers on his team. They are all veterans of the federal criminal justice system. They know very well that as executive branch personnel they must follow OLC’s opinions that a president cannot be indicted.

And these lawyers know very well that no court has ever ruled that a president may be subpoenaed to testify in a criminal proceeding involving his own conduct.

The lawyers on Mueller’s team also know that the grand jury cannot be used to obtain evidence except for the criminal process. And yet, Special Counsel Mueller has threatened the president with a grand jury subpoena.

The Senate needs to pass a bill to protect the constitutional authority of the presidency, not the bad faith conduct of the special counsel.