Special counsel Robert S. Mueller III departs St. John's Episcopal Church, across from the White House, on March 24, 2019. (Cliff Owen/Associated Press)

David E. Kendall, a lawyer at Williams & Connolly, represented President Clinton during the independent counsel investigation led by Kenneth Starr. He currently represents both the former president and 2016 Democratic presidential nominee Hillary Clinton.

Special counsel Robert S. Mueller III conducted a highly professional and comprehensive investigation of whether the campaign of Donald Trump conspired with Russians to undermine the 2016 election and whether, as president, he obstructed that investigation. Mueller’s conclusions on conspiracy are debatable, but they should be respected as a traditional prosecutorial judgment.

But the failure to draw any conclusion on whether the president obstructed justice was a massive dereliction of the special counsel’s duty, and the report’s explanation of this failure is both incoherent and illogical.

The second volume of the report lays out the Mueller’s analysis of 10 instances of possible obstruction of the Russia probe by Trump. On four of these, Mueller concludes that there is “substantial” evidence to support a prosecution. But it draws no final conclusion, declaring instead that “difficult issues . . . prevent us from conclusively determining that no criminal conduct occurred. Accordingly, while this report does not conclude that the President committed a crime, it also does not exonerate him.”

It did not take long for Attorney General William P. Barr and Deputy Attorney General Rod J. Rosenstein to resolve those “difficult issues” and decree that the president did not obstruct justice.

This exoneration was made possible by a massive flinch: Mueller failed to follow Justice Department regulations, which say a special counsel “shall provide” the attorney general a confidential report “explaining the prosecution or declination decisions reached by the Special Counsel.” The special counsel is not authorized to bypass the required binary decision; he must decide to prosecute or not.

Mueller’s explanation for this flinch does not withstand scrutiny. He notes that the Justice Department’s Office of Legal Counsel (OLC) has held that a sitting president may not be criminally charged, but this was well known when he was appointed. Besides, the OLC ruling does not preclude alternative action when evidence of criminal conduct by the president is discovered, and there is clear precedent for such action: In 1973, the Watergate special prosecutor transmitted to Congress a “road map” of evidence developed in its investigation of President Richard M. Nixon, with the approval of the chief judge of the district court. It is no excuse to declare that a criminal charge would “potentially preempt constitutional processes for addressing presidential misconduct,” since Mueller could have submitted a similar “road map” without filing criminal charges.

The report’s contention that “fairness” would be violated by a prosecutorial accusation in circumstances where the president would have no “adversarial opportunity for public name-clearing before an impartial adjudicator” also rings hollow. The report proceeds to lay out nearly 150 pages of evidence of possible obstruction, concluding that much of it is “substantial.” Even with then-FBI director James B. Comey’s smear of Democratic presidential nominee Hillary Clinton in 2016, there was at least a clear determination that “no prosecutor” would have brought criminal charges under the circumstances.

Likewise, the fact that “difficult issues” are presented when determining whether criminal conduct occurred is no justification, since prosecutors frequently must resolve complex questions when determining whether to indict. Mueller was uniquely situated to make an informed judgment, since he had conducted a massive investigation, heard the witnesses and analyzed the evidence.

In fact, some of the four instances where Mueller found “substantial” evidence of obstruction do not actually appear “difficult” at all. For example, the report asserts that in June 2017, Trump met one-on-one with former aide Corey Lewandowski and instructed him to tell then-Attorney General Jeff Sessions that he would have to “unrecuse” himself to take charge of the Russia investigation and mandate that it would be limited to future election interference only. Trump allegedly directed Lewandowski to instruct Sessions to declare that Sessions knew “for a fact” that “there were no Russians involved with the campaign” because he “was there.” And Trump ordered Lewandowski to direct Sessions to explain that Trump should not be subjected to an investigation “because he hasn’t done anything wrong.” Lewandowski declined to make these requests, instead passing them to a current White House aide, who also declined. This is not a hard case. The conduct is more aggravated than that recorded on the “smoking gun” tape: Nixon’s 1972 direction that the CIA director tell the FBI that the Watergate investigation involved important national security matters and should not be pursued.

Mueller’s failure to come to a conclusion about obstruction is even more bizarre, since it analyzes at length the contention (espoused by Barr in a June 2018 memo, before he became attorney general) that a president cannot be guilty of obstruction when what is at issue is “facially lawful” presidential conduct, such as firing prosecutors or ordering criminal investigations terminated. Mueller demolishes this contention, concluding that overwhelming precedent supports the theory that “the obstruction-of-justice statutes can validly prohibit a President’s corrupt efforts to use his official powers to curtail, end, or interfere with an investigation.” Though the Mueller report said it was not exonerating the president, it left the coast clear for Barr to do just that.

In leaving Barr — who lacks the independence that the special counsel role was designed to preserve — to render judgment on the evidence and the law, Mueller abdicated his duty. Congress should now interview Mueller and his senior staff. Each of the 10 instances of possible obstruction should be reviewed and the following question asked and answered: Allowing for the differences between the president and a private citizen, had analogous conduct been engaged in by the citizen, would a grand jury indictment have been sought for obstruction of justice?

This would provide, albeit belatedly and bootlessly, a knowledgeable and neutral judgment on the president’s conduct during the Russia investigation.