(CNN) Former Attorney General William "Bill" Barr, President Donald Trump's pick to lead the Justice Department, reached a decisive and controversial conclusion that Trump's interactions with ex-FBI Director James Comey would not constitute obstruction of justice, according to a copy of a newly released June 2018 memo to senior Justice officials.

The fact that Barr weighed in on such a sensitive issue and would be poised to oversee special counsel Robert Mueller's work, if confirmed as attorney general, will undoubtedly now thrust his nomination into greater controversy. Barr discussed the memo with Trump and told him it would likely come up during his Senate confirmation, a source familiar with the discussions told CNN.

Barr has not shied away from defending Trump's firing of Comey , but the June 8 memo -- first reported by The Wall Street Journal and provided to lawmakers late Wednesday -- offers a detailed analysis of one of the most consequential episodes of Trump's presidency, concluding that while he's "in the dark about many facts," Mueller's obstruction inquiry was "fatally misconceived." Barr adds that Trump asking Comey to let go of the investigation into former national security adviser Michael Flynn and later firing Comey were within his powers as head of the executive branch.

"Mueller should not be able to demand that the President submit to an interrogation about alleged obstruction," Barr wrote. "If embraced by the Department, this theory would have potentially disastrous implications, not just for the Presidency, but for the Executive branch as a whole and the Department in particular."

The full repercussions of the President's behavior toward Comey are yet to be resolved, as the matter is still under investigation by Mueller.

Read More