Alex Brandon / AP

Special Counsel Robert Mueller’s report contains numerous factual revelations and, even with the redactions, rounds out what was so far known about the president’s openness to a political alliance with Russia and his dedication to obstructing any inquiry into “collusion.” Weeks will pass before the full significance of these investigative findings can be assessed. In the meantime, the report is itself evidence: a clear indication that almost 50 years after Watergate, major barriers have now settled into place against presidential accountability for serious misconduct.

First, note the impact of the two Office of Legal Counsel (OLC) opinions immunizing the president from prosecution while in office. In a striking passage, Mueller suggests a reluctance to reach a final judgment about the president’s criminal liability if he cannot be indicted and tried—and therefore cannot defend himself.

These OLC opinions, each written in administrations of presidents who faced impeachment, have virtually no credibility. They do not purport to reflect anything like established or even clear law. It is perhaps somewhat unfair and overly simplistic to say that the premise of the opinions is that the president is too important to face accountability under the criminal-justice system. But it is neither entirely unfair nor wildly oversimplistic.

The notion that the presidency itself is a shield against liability shows up again in Mueller’s treatment of the Trump team’s claims that the president has the constitutional authority to fire subordinates at will, dismissing the likes of former FBI Director James Comey (and had Donald Trump had his druthers, Mueller), and that his motive, however corrupt, is irrelevant. This is a position that Attorney General William Barr shares. He holds it so intensely that he expressed himself pro bono on the subject in a written memorandum provided to the administration in the middle of the special counsel’s investigation.

Mueller does attempt to refute this expansive line of argument about presidential immunities. He writes that while the president “has broad discretion to direct criminal investigations,” authority “coexists with Congress’… power to enact laws” to protect against interference with the criminal-justice system. He disputes any suggestions that prosecuting the president for obstruction of justice would in some way disrupt the balance of power between the two branches. He also challenges the suggestion that the application of criminal laws in this context would undermine the president’s ability to perform his core constitutional responsibilities. He sensibly concludes that a “general ban on corrupt action does not unduly intrude on the president’s responsibility” to faithfully execute the law.

But for all of this, Mueller displays considerable hesitation about applying his reading of the constitutional law too aggressively. He feels he must acknowledge that because the conduct in question “involved actions by the president,” his analysis remained complicated by constitutional considerations. And, somewhat ambiguously, he notes that it should not matter that the president conducted some of the obstructive conduct in full public view, but also that it is “more difficult to establish that public-facing acts were motivated by a corrupt intent.” All in all, he concludes, the questions presented by the obstruction phase of the case, some of them not definitively resolved by the Department of Justice or the courts, weigh against an affirmative finding that the president violated the law.

Did Mueller split the difference? Did he leave the report as a solid rejoinder to Trump and his lawyers’ claims of vast presidential immunity while declining to force a test of this position with a clear statement of presidential criminal misconduct in this particular case? It is, of course, impossible to know his intentions. There is, however, a marked difference between the strong constitutional stakes that Mueller plants in the ground and the more reticent position that he takes on the evidence.

In other words, the report is strong in theory, but perplexing in application.

Of course, a criminal prosecution of a president cannot proceed without recognition that it is no small matter for a prosecutor to put at risk a democratically elected government. At the same time, the report contains a wealth of evidence that the president disregarded the law whenever it suited him, and especially whenever it was in his personal and political interest.

In any normal case like this, the amount of detail of bad or shady character would have swung the case very much against the president. He routinely lies and urges other people to lie; he directed his White House counsel to fabricate evidence that he had not ordered the counsel, as he indeed had, to arrange for Mueller’s dismissal. While it is true that prosecutors should prosecute crimes and not people, they rarely fail to be affected by evidence that the person under investigation routinely hatches criminally questionable schemes. The Mueller report certainly seems to support the proposition that a president can expect the benefit of the doubt in this respect.

Here, after all, is a report in which the prosecutor concludes that the “President’s efforts to influence investigation were mostly unsuccessful, but that is largely because the persons who surrounded the president declined to carry out orders or accede to his requests.” This is a remarkable statement. If he were still the chief executive of the Trump Organization, it would not have worked well for Trump to defend against multiple criminal accusations by noting that his staff sometimes intervened to stop him. For the chief executive of the United States, this peculiar argument seems to have some bite.

In fairness to Mueller, his report is a product of the cycle of adjustments made to the mechanism for investigating presidential misconduct. The Watergate episode suggested the need for an independent process, free of conflict of interest. This ushered in the period of the “independent counsel,” which later came to be seen as fraught with dangers of partisan overreach, and a presidency hobbled beyond reason by sustained, expensive, and at times ill- motivated investigations. Once that statute was allowed to die, the special-counsel regulations under which Mueller operated were meant to provide some measure of independent enforcement, while restricting the avenues for partisan misuse.

Now a special counsel reports to the attorney general, making him an employee bound to follow his superior’s orders and to comply with Justice Department policies and standards, including the OLC immunity opinions. He reports his conclusions on a confidential basis: Only the attorney general can authorize a public release. The special counsel must refrain from expressing a judgment about potential impeachable offenses. Just as the independent-counsel law after the Watergate period was an answer to the lawlessness of the Nixon administration, so the special-counsel rules respond to the excesses of Ken Starr and the Clinton impeachment. Mueller was operating within a network of built-in limitations.

It may then be counted as a major part of Mueller’s public service that he wrote an extensive report with massive detail and took specific issue with expansive claims of executive immunity. Especially in the conclusion of the report, in the refusal to “exonerate” the president of the obstruction charges, Mueller seems to have something to say. He just declines to go further.

Mueller’s restraint reveals the continued imperfection of the system for containing presidential misconduct. Trying yet one more time to fix that system is an urgent task. Only days ago, Robert Caro, Lyndon B. Johnson’s biographer, said memorably that “you don’t know if this is an aberration or not, if Trump is something outside, and he’s going to lose, and we’ll forget.” Then he asked: “Or is he the first of the mad Roman emperors?”

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