The White House last month lodged a formal complaint with the Justice Department over the findings of special counsel Robert S. Mueller III — and made clear that President Trump believes he retains the right to assert executive privilege over material contained in the report, despite its public release.

The five-page letter was authored by Emmet Flood, who has handled the Mueller investigation for the White House counsel’s office, and submitted to Attorney General William P. Barr on April 19, the day after Barr released a redacted version of the report.

The letter was provided to The Washington Post by a White House official one day after Barr criticized Mueller during a contentious appearance in front of the Senate Judiciary Committee. The attorney general described a letter from the special counsel asking him to release summaries of his report as “snitty” and said he was confused by Mueller’s decision that he could not come to a conclusion at the end of his obstruction-of-justice inquiry.

A redacted version of special counsel Robert S. Mueller III's report was released to the public on April 18. Here's what's in it. (Brian Monroe, Monica Akhtar/The Washington Post)

In his report, Mueller wrote that he believed that because a Justice Department policy holds that the president cannot be indicted while in office, the special counsel’s office could not make an assessment on whether the president had broken the law.

“While this report does not conclude that the President committed a crime, it also does not exonerate him,” Mueller wrote in his 448-page report, which laid out evidence gathered about potential acts of obstruction by Trump.

In his April 19 letter, Flood accused Mueller of exceeding his authority by spilling into public view a recitation of facts far more detailed than what is typically included in criminal indictments. He described the report as “prosecutorial curiosity — part ‘truth commission’ report and part law school exam paper.”

Both the Justice Department and the special counsel’s office declined to comment.

In the letter, Flood offered a scathing critique of Mueller’s report, writing that the special counsel team abandoned the normal burden of proof that requires prosecutors to establish crimes beyond a reasonable doubt.

The refusal to “exonerate” the president, he wrote, turned the presumption of innocence on its head.

“Because they do not belong to our criminal justice vocabulary, the SCO’s inverted-proof-standard and ‘exoneration’ statements can be understood only as political statements, issuing from persons (federal prosecutors) who in our system of government are rightly expected never to be political in the performance of their duties,” Flood wrote in the letter, which was first reported by CNN.

He said that Mueller’s lengthy report showed his team had “failed in their duty to act as prosecutors and only as prosecutors.

Before the release of Mueller’s report, the White House did not assert executive privilege over the document or request redactions.

In his letter, Flood wrote that the White House declined to assert the privilege with a “measure of reluctance born of concern for future Presidents and their advisors.”

But he made clear that the White House did not believe this choice meant they have closed the door on asserting executive privilege over the same material in the future.

In particular, he wrote that the release of the report does not affect the president’s ability to instruct advisers to refuse to appear before congressional committees.

“It is one thing for a President to encourage complete cooperation and transparency in a criminal investigation conducted largely within the Executive Branch,” he wrote. “It is something else entirely to allow his advisors to appear before Congress, a coordinate branch of government, and answer questions relating to their communications with the President and with each other.”

The House Judiciary Committee has issued a subpoena to former White House counsel Donald McGahn, who was a key witness to several episodes Mueller explored as he looked at whether Trump obstructed justice.

The White House has objected to McGahn’s appearance. In an interview with Fox News on Thursday, Trump said he’d already had McGahn testify for more than 30 hours, referring to the time the former White House lawyer spent with Mueller’s investigators. “Congress shouldn’t be looking anymore. This is all. It’s done,” Trump said.

If McGahn chooses to defer to guidance from White House lawyers, the issue will likely result in a lengthy court battle that will test the limits of the president’s executive powers.