Fox News senior judicial analyst Judge Andrew Napolitano reacted Monday on Fox Nation to the conclusion of the 674-day investigation by Special Counsel Robert Mueller.

Attorney General William Barr released the "principal conclusions" of Mueller's probe in a four-page letter to lawmakers Sunday, which stated definitively that Mueller did not establish evidence that Trump's team or any associates of the campaign conspired with Russia to sway the 2016 election.

According to Barr's letter, however, Mueller's report did not reach a conclusion on whether the president obstructed justice, and left that decision to Barr and officials at the DOJ -- who determined there was insufficient evidence of obstruction.

But Barr also wrote, "The Special Counsel states that 'while this report does not conclude that the President committed a crime, it also does not exonerate him.'" 

Napolitano said it was a "head-scratcher" for Barr to reveal that difference of opinion with Mueller on the obstruction issue. 

The judge said it's not uncommon for prosecutors to have different opinions on the same evidence and statutes, but it's "unheard-of for the existence of these differences to be revealed publicly."

Napolitano said that by doing so, Barr "is opening a can of worms for the president and throwing a lifeline to House Democrats" for more investigations of obstruction. 

"The Democrats will reason, quite properly in my view, that there must be something there or Mueller would have exonerated the president on obstruction, just as he did on conspiracy. So is our long national nightmare over or is it just beginning?" he asked.

Watch the monologue above and sign up for a free trial on Fox Nation to see the full episode of "Liberty File" with special guest Ken Starr. 

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