Barr can't without going to jail. Trump can't without being impeached for obstruction of justice.

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As Barr noted in his letter to Congress, he can't send Muller's report because it contains Grand Jury testimony. That can't be released. There is also large chucks of stuff that is unreleasable because of ongoing investigations in various jurisdictions. The clowns calling for immediate release understand this just because they want him to get in trouble for releasing it.

Total lie.

There are congressmen, on the intelligence and perhaps judiciary committees, that have the necessary security clearances to not only read the documents, but can also make redactions.