Can the president be indicted?

The Supreme Court has never answered that question, either. It heard arguments on the issue in 1974 in a case in which it ordered President Richard M. Nixon to turn over tape recordings, but it did not resolve it.

Reports that President Donald Trump asked James Comey, then the FBI director, to shut down an investigation into his former national security adviser, Michael Flynn, prompted accusations that the president may have obstructed justice. Robert Mueller, the former FBI director who has been appointed special counsel to look into ties between the Trump campaign and Russia, will presumably investigate the matter.

But would the Constitution allow Mueller to indict Trump if he finds evidence of criminal conduct?

The prevailing view among most legal experts is no. They say the president is immune from prosecution so long as he is in office.

“The framers implicitly immunized a sitting president from ordinary criminal prosecution,” said Akhil Reed Amar, a law professor at Yale.

Note the word “implicitly.” Amar acknowledged that the text of the Constitution did not directly answer the question. “It has to be,” he said, “a structural inference about the uniqueness of the president himself.”

The closest the Constitution comes to addressing the issue is in this passage, from Article I, Section 3: “Judgment in cases of impeachment shall not extend further than to removal from office, and disqualification to hold and enjoy any office of honor, trust or profit under the United States: but the party convicted shall nevertheless be liable and subject to indictment, trial, judgment and punishment, according to law.”

This much seems clear: The president and other federal officials may be prosecuted after they leave office, and there is no double jeopardy protection from prosecution if they are removed following impeachment.

However, “whether the Constitution allows indictment of a sitting president is debatable,” Brett M. Kavanaugh, who served on the staff of Ken Starr, the independent counsel who investigated President Bill Clinton, wrote in a 1998 law review article. Kavanaugh, who is now a federal appeals court judge, also concluded that impeachment, not prosecution, was the right way to address a sitting president’s crimes.

The most prominent dissenter from the prevailing view is Eric M. Freedman, a law professor at Hofstra University and the author of a 1999 law review article that made the case for allowing criminal prosecution of incumbent presidents.

Freedman demonstrated that the issue had divided the founding generation and argued that granting sitting presidents immunity from prosecution was “inconsistent with the history, structure and underlying philosophy of our government, at odds with precedent and unjustified by practical considerations.”

He pointed out that other federal officials who are subject to impeachment, including judges, have been indicted while in office. Courts have rejected the argument that impeachment is the sole remedy for such officials.

But Amar said that presidents were different.

“If you’re going to undo a national election, the body that does that should have a national mandate,” he said. “Even a federal prosecution would follow only from an indictment from a grand jury sitting in one locality.”

Vice President Spiro T. Agnew, facing a grand jury investigation that would lead to his resignation in 1973, argued that he was immune from prosecution while in office. Impeachment, he said, was the only remedy.

The Justice Department, in a brief signed by Solicitor General Robert Bork, disagreed. But, though the question was not before the court, Bork added that “structural features of the Constitution” barred prosecutions of sitting presidents.

Since the president has the power to control federal prosecutions and to pardon federal offenses, Bork wrote, it would make no sense to allow the president to be prosecuted until after he is removed from office and forfeits those powers. (Bork would go on to become a federal appeals court judge and an unsuccessful nominee to the Supreme Court.)

A year later, Leon Jaworski, the Watergate special prosecutor, took a less categorical position.

“It is an open and substantial question whether an incumbent president is subject to indictment,” he told the Supreme Court during his successful quest to obtain the White House recordings that contributed to Nixon’s resignation.

In a series of memorandums, the Justice Department’s Office of Legal Counsel concluded that indicting a sitting president would violate the Constitution by undermining his ability to do his job. Those memos, too, though, said the answer was a matter of structure and inference.

“Neither the text nor the history of the Constitution ultimately provided dispositive guidance in determining whether a president is amenable to indictment or criminal prosecution while in office,” a 2000 memo said, summarizing an earlier one. “It therefore based its analysis on more general considerations of constitutional structure.”

The Justice Department’s regulations require Mueller, the special counsel, to follow the department’s “rules, regulations, procedures, practices and policies.” If the memos bind Mueller, it would seem he could not indict Trump, no matter what he uncovered.

But Andrew Manuel Crespo, a law professor at Harvard, has questioned whether the special-counsel regulations should be read that broadly. The regulations, he wrote on Take Care, a law blog, “focus more on administrative protocols and procedures than on legal analyses, arguments or judgments.”

Even if Mueller has a measure of discretion, Amar said, the right process for assessing Trump’s conduct, should it come to that, is the one described in detail in the Constitution: impeachment.

“Much of the recent pontificating about the technical elements of obstruction of justice is quite beside the point,” he said. “Donald Trump is to be judged by the House and the Senate, who are in turn judged on Election Day by the American people more generally.”