RUTHFULLY YOURS

Franklin v. Massachusetts (1992) dealt with the question of when statutes enacted by Congress apply to the president. The ruling noted that “the President is not explicitly excluded” from the Administrative Procedure Act, “but he is not explicitly included, either.” Under such circumstances, “out of respect for the separation of powers and the unique constitutional position of the President . . . textual silence is not enough to subject the President to the provisions.”

More fundamentally, in Nixon v. Fitzgerald (1982), the court held that separation of powers demands absolute immunity from civil lawsuits for acts falling within the “outer perimeter” of the president’s official responsibilities. Absolute immunity is necessary because the president “occupies a unique position in the constitutional scheme,” and the specter of litigation “could distract a President from his public duties.” That applies with even greater force to the threat of criminal prosecution.

Special counsel Jack Smith argues that “no President need be chilled in fulfilling his responsibilities” because there are “strong institutional checks to ensure evenhanded and impartial enforcement of the law,” including grand jury indictment, due process and the government’s burden of proving guilt beyond a reasonable doubt. But even if the prospect of conviction is remote, the threat of prosecution impairs the presidency.

Further, the most important institutional check, the norm against politicized prosecutions, has so broken down that not only Mr. Smith but district attorneys in New York and Atlanta have rushed to bring Mr. Trump to court. Imagine how other presidents might have fared if they had to worry about prosecution for official acts:

• Abraham Lincoln suspended habeas corpus without congressional authorization. In Ex Parte Merryman (1861), Chief Justice Roger Taney, acting as a circuit judge, held that the power to suspend habeas lies solely with Congress. Lincoln ignored Taney’s ruling and continued his suspension of habeas until the end of the Civil War. No one suggested that Lincoln be prosecuted for false imprisonment, false arrest or kidnapping.

• Harry S. Truman seized domestic steel plants during the Korean War, violating statutes that authorized the president to seize private property only in narrow circumstances. The Supreme Court declared his actions unconstitutional in Youngstown Sheet & Tube Co. v. Sawyer (1952). But no federal prosecutors suggested they could prosecute him for “conspiracy against rights,” or “conspiracy to commit an offense against the United States,” the charges Mr. Smith has brought against Mr. Trump.

• Bill Clinton, George W. Bush, Barack Obama and Joe Biden all unilaterally ordered military actions as commander in chief. Critics accused them of usurping Congress’s power to declare war, but nobody seriously suggested that they be prosecuted for murder, torture, war crimes or misappropriation of government resources.

The president isn’t the only official to enjoy immunity for official acts. In Yaselli v. Goff (1927), the Supreme Court affirmed a lower court’s conclusion that federal prosecutors have absolute immunity from civil liability because the “public interest requires that persons occupying such important positions . . . should speak and act freely and fearlessly in the discharge of their important official functions.” In Kalina v. Fletcher (1997), the justices held that even under Section 1983—a civil-rights law authorizing lawsuits against state officials who violate federal constitutional rights—prosecutors enjoy absolute immunity for acts undertaken in their “role as an advocate.” This is because that role is unique to prosecutors, and the public’s interest “in protecting the proper functioning of the office, rather than the interest in protecting its occupant, . . . is of primary importance.”

The court reached the same conclusion about judges in Pierson v. Ray (1967), which held that Section 1983 didn’t abrogate judges’ absolute immunity for “acts committed within their judicial jurisdiction,” because such immunity is “for the benefit of the public, whose interest it is that the judges should be at liberty to exercise their functions with independence and without fear of consequences.”

In Gravel v. U.S. (1972), the justices held that the Speech and Debate Clause extends absolute immunity to members of Congress and their aides for official actions. This is to protect a member of “a co-equal branch of the government” from “executive and judicial oversight that realistically threatens to control his conduct as a legislator.”

Like prosecutors, judges and congressmen, a president threatened with prosecutions for official acts couldn’t exercise his duties with full vigor. Unlike those other officials, the president is the singular head of a branch of government, making his ability to exercise his powers all the more essential.

That leaves the question of whether the actions for which Mr. Trump was charged were official or, as Mr. Smith asserts, private. In McDonnell v. U.S. (2016) the court held that an “official act” is an action on any matter that is “pending . . . before a public official,” and includes the president’s “using his official position to exert pressure on another official, knowing or intending that such advice will form the basis for an ‘official act’ of another official.”

Mr. Trump acknowledges that “no court has yet addressed the application of immunity to the alleged facts of the case.” The justices should draw a line and extend absolute criminal immunity to actions within the outer perimeter of the president’s duties. Then it would be for the lower courts to decide on which side of the line these actions fall.

Mr. Rivkin served at the Justice Department and the White House Counsel’s Office during the Reagan and George H.W. Bush Administrations. Ms. Foley is a professor of constitutional law at Florida International University College of Law. Both practice appellate and constitutional law in Washington.