That letter, which has been scrutinized repeatedly, offers very little by way of direct input from Mueller himself. The bulk of it is devoted to Barr’s self-described “[summary of] the principal conclusions” that Mueller reached in that investigation. Those are primarily twofold: that Mueller “did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities” (in Mueller’s words) and that while Mueller “does not exonerate” Trump on questions of obstruction of justice (again, quoting Mueller via Barr), that Barr and Deputy Attorney General Rod J. Rosenstein determined that the evidence obtained by Mueller “is not sufficient to establish that the President committed an obstruction-of-justice offense.”

And so, Trump's various celebrations of Mueller's work, as on Monday morning.

Americans have been skeptical of this presentation of what Mueller found, in part because so little of Mueller’s work has been shown. There’s been a broad call for the report written by Mueller’s team to be released to the public, to allow Americans to assess for themselves what the special counsel found. Barr has expressed willingness to release the document — but only once he and the Department of Justice have redacted material that fits into a few broad categories, including some information related to grand-jury proceedings.

Barr’s stated position is that the redactions will be as narrow as they can be to ensure transparency. But once the redacted report is released, it’s safe to assume that some skepticism about what was withheld will continue.

Particularly given Barr’s track record, as New York University professor of law Ryan Goodman wrote on Monday at the site Just Security, where he’s a co-editor-in-chief.

Goodman, who is a former Defense Department special counsel, details a remarkably similar fight from 1989 in which Barr, then head of the Justice Department’s Office of Legal Counsel, was involved. The OLC had determined that the FBI was allowed to take people into custody in foreign countries without the consent of those countries' governments — a ruling that seemed to pave the way, Goodman notes, for the eventual arrest of former Panamanian leader Manuel Antonio Noriega.

This was a contentious position to take, and Barr was asked to provide the memo offering the detailed legal rationale for allowing such detentions. He declined, instead offering a 13-page document that “summarizes the principal conclusions.” When Congress, and then The Washington Post, obtained the full opinion in 1991, it was quickly noted that several conclusions from the full document hadn’t been included in Barr’s summary. Foremost among them was that the opinion authorized the president of the United States to ignore the United Nations Charter.

Goodman quotes Boston University's Jeanne Woods, writing in 1996: “Barr’s congressional testimony attempted to gloss over the broad legal and policy changes that his written opinion advocated.”

Goodman spoke with The Post by phone on Monday.

"What happened in 1989 is that Barr, in a sense, actually provided a redacted version of the underlying OLC opinion,” he said. “That's the problem, because the redactions of what he omitted are very significant for legal practice — yet he told the Congress that he was including all of the, quote unquote, 'principal conclusions' that time around as well.”

"I think that for me it's significant in that breeds a lot of distrust of relying on Barr's assurances that he's handling this process in a way that's faithful to the principles that he's announced,” he added, “and will let the public know what the public should know at this time.”

While Barr suggested in testimony last week that he would indicate the broad principles under which various parts were redacted, Goodman noted that he can choose to interpret his redaction authority in broad terms — something that would be hard even for members of Congress to evaluate as appropriate.

Asked if he felt Barr was acting in good faith in 1989, Goodman hesitated.

"I think it's difficult to imagine that Barr didn't know what he was doing in failing to inform the Congress that he had concluded that the president of the United States could violate the U.N. Charter,” he said. “In fact, that proposition has proved to be highly controversial ever since the OLC opinion was publicly released and significant executive branch practice turns on that proposition.”

He later added that the OLC opinion has come to be seen as “a notorious opinion or a infamous, highly controversial opinion.”

There was one specific reason to think that Barr might be more willing to hew to a narrow set of redactions this time, Goodman said: a muscular Congress.

“In 1989, the Congress appeared somewhat shy to actually subpoena the full opinion,” he said, noting that it took nearly two years for them to do so, by which point Barr had left his position at the OLC. “Here you have the House Judiciary Committee already authorizing to subpoena the full Mueller report. That may change Barr’s calculation because he might think, this time around, the full document will be revealed at the same period of time that he’s still in office.”

Unless, he added, the administration fights the subpoena. In which case we may be left with another extended period in which it’s unclear how accurately Barr’s conveying what Mueller said — a period overshadowed by knowing that he’s underplayed or obscured significant information in the past.