From the Washington Post:
The redacted Mueller report released Thursday makes clear that he and his prosecutors viewed the OLC opinion to mean they also could not come to a conclusion about whether the president had committed a crime because it would violate Justice Department standards of fairness to make such an accusation — even secretly — without giving the person a chance to fight the accusation. Barr disagreed.
Mueller’s approach to the question of whether the president tried to obstruct justice has created tension inside the Justice Department, according to current and former officials. Privately, some senior officials at the Justice Department have been unhappy that Mueller did not reach a conclusion about whether Trump’s conduct rose to the level of a crime, said the officials, who like others spoke on the condition of anonymity because of ongoing sensitivity surrounding the probe.
...
But Ray said he suspected another reason for Mueller’s punt: He did not want to put Barr in a position of having to overrule him.
“I do think it’s a component of the special counsel’s thinking that if he had gone that direction, he was well aware of the fact that the Department of Justice’s view would be and the attorney general’s decision would be to overrule it, and that is not a desirable place for the country to be,” Ray said. “I’m sure the attorney general didn’t appreciate the fact that he was put in the position of having to resolve the matter either, but given those two choices, I think it was better to have left it unresolved and have the attorney general take it from there.”
https://www.washingtonpost.com/world/national-security/how-a-legal-dispute-between-mueller-and-barr-drove-the-end-of-the-trump-probe/2019/04/19/1781807e-623e-11e9-9ff2-abc984dc9eec_story.html
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So looks like Mueller punted to Congress on the obstruction question so that he would not be overruled by Barr. But Barr ended up overruling him anyway by concluding on his own there was no obstruction.
Still, Mueller gave us a detailed roadmap to impeachment on obstruction, citing overwhelming evidence. The House must now move to impeach Trump. We must get everyone on record as stating that a President WHO WELCOMES A FOREIGN ADVERSARY'S ATTACK IN ORDER TO WIN ELECTION, THEN FLAGRANTLY OBSTRUCTS THE INVESTIGATION INTO THAT ATTACK must not sit in the White House.
This isn't a political game. This is about our country.
If we let this stand, it means future presidential candidates can collude with foreign adversaries to win election, and can obstruct justice WITH IMPUNITY. The right has demonstrated they will not punish their candidates for such conduct. We cannot follow the example of the deplorables. We must stand for the rule of law.
The 2020 election is only 18 months away. There is no time for months-long tedious investigations or fighting the administration in court for more documents. Mueller knew this, which is why he abruptly ended his investigation and handed obstruction charges off to Congress. Mueller has given us everything we need to impeach, and just barely the time to do it. We must start impeachment hearings now. This is what the House members swept in by the Blue Wave were elected to do.
If House Democrats fail to do their job, it will depress the Democratic turnout in 2020 and Trump will get reelected, and we will lose our democracy.