Four Supreme Court cases defining the limits of congressional investigatory authority ultimately will determine whether Treasury Secretary Steven Mnuchin will be required to give President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE’s tax returns to the House of Representatives. These cases also control whether Congress can compel former White House counsel Don McGahn, Attorney General William Barr or other executive department officials to testify or comply with subpoenas. How the current justices respond to these cases and rules, in terms of the scope of congressional investigatory power, will be a defining moment for Chief Justice John Roberts and his court.

The House has issued several requests to the Trump executive branch, including for the president’s federal taxes. In rebuffing this demand, Mnuchin wrote to Congress that its request was a “politically motivated abuse of the law [that] violates our Constitution — and serves no legislative purpose.” Does Mnuchin get to make this call on the motives or purposes of Congress? Supreme Court precedent suggests no.

ADVERTISEMENT

In McGrain v. Daugherty (273 U.S. 135, 1927), the court had its first opportunity to rule on the scope of congressional investigatory power. Acknowledging that no express clause of the Constitution conferred or delineated this power, the court nonetheless affirmed it in this case by declaring: “We are of opinion that the power of inquiry — with process to enforce it — is an essential and appropriate auxiliary to the legislative function.”

The courts consistently have protected congressional investigatory power, permitting Congress to use the judicial power of contempt to enforce it as consistent with separation of powers. This is essentially what the court affirmed in McGrain in 1927. The investigatory power was expressly mentioned in the Legislative Reorganization Act of 1946.

Congress has used the power of investigation during its entire history, beginning with Washington’s presidency. Its use became most prominent with the House Un-American Activities Committee (HUAC) before World War II, and then in the 1950s in a Senate subcommittee, notoriously led by Sen. Joseph McCarthy (R-Wisc.). Congress used its investigatory power to gather information about alleged communist infiltration into the State Department and track down any communist activity in American society.

These hearings, especially those over which McCarthy presided, often subpoenaed witnesses, accusing them of being communists, and then asked them to name other communist sympathizers. The “witch hunts,” as some described them, often included witnesses “taking the Fifth,” or refusing to testify, claiming a right against self-incrimination.

ADVERTISEMENT

Eventually the court was called upon to examine the authority of Congress to conduct such hearings. In Watkins v. United States (354 U.S. 178, 1957), the court narrowed the boundaries for these investigations, indicating that Congress could not engage in hearings simply for the sake of exposing individuals. The hearings must have a purpose, and they are required to respect the First Amendment rights of witnesses. In Watkins, the court seemingly clipped the wings of Congress — but threats by the latter to retaliate against the judiciary, and efforts to overturn the decision, paid off merely two years later.

In Barenblatt v. United States (360 U.S. 109, 1959), the court appeared to back down from Watkins. Here, in looking at the alleged communist activity of a student at the University of Michigan, a divided court affirmed the broad investigatory power it had affirmed in McGrain, and ruled that the investigation struck an appropriate balance between this authority and the First Amendment rights of the witness. It is not clear that Congress was doing anything differently than before — it simply looked like the court blinked.

Barenblatt did not given Congress a blank check to investigate. The court introduced a new concept — that of the “balancing test.” This means that when both individual and governmental interests and rights are at stake, a balance must be struck to give priority to whichever appears to be more necessary. However, this balancing test refers to investigations of private citizens, not executive branch officials.

U.S. v. Nixon, (418 U.S. 683, 1974) addressed this balance in looking at whether Nixon could refuse to hand over the Watergate tapes to a federal prosecutor. Nixon claimed executive privilege as grounds to refuse. Although the Supreme Court ruled that executive privilege existed as a feature of separation of powers, it was not an absolute power or privilege. It had to be balanced against the needs of the judicial branch, criminal justice and due process of law, to secure all the relevant facts and determine whether criminality had occurred within the executive branch. Simply put, for the purposes of compelling executive-department compliance with subpoenas, the separation of powers’ needs of the judicial branch to perform its functions and probe criminal behavior outweighed any claims of privilege the latter had.

Given the above four cases, the law seems clear that the courts should give broad deference to Congress to use its investigatory power to compel testimony for the purposes of oversight and to ascertain possible criminality. Moreover, the courts are unlikely to question the motive or purpose of a congressional investigation.

Current precedent favors Congress and, should the Supreme Court rule on matters regarding President Trump, he should lose. Whether this will happen is a potential true test for Chief Justice Roberts and this Supreme Court. If it were to rule for the Trump executive branch, that would be a clear sign of its partisan political nature and call into question its legitimacy, neutrality and legacy.

David Schultz is a professor of political science at Hamline University in St. Paul, Minn. Follow him on Twitter @ProfDSchultz.