William Barr, tapped by President Donald Trump to take on the mantle of attorney general, reportedly sent an “unsolicited memo” to the Justice Department earlier this year in which he lambasted part of special counsel Robert Mueller’s ongoing Russia investigation.

Barr said Mueller’s probe into potential obstruction of justice by President Trump was based on a “fatally misconceived” theory, The Wall Street Journal reported Wednesday.

It’s not the first time that Barr, who would oversee Mueller’s investigation as attorney general, has been critical of the probe. He told The Hill last year that “leaks” from the special counsel’s team “raise questions as to whether there is an agenda.” He’s also suggested that Mueller’s team was not politically “balanced” because some members had donated to Democratic candidates.

According to the Journal, Barr sent the 20-page memo — which the outlet said it had reviewed — to Deputy Attorney General Rod Rosenstein in June. In it, Barr argued that, based on his understanding of the facts, Trump had been acting well within his authority as president when he allegedly suggested to then-FBI director James Comey that an investigation into former national security advisor Michael Flynn should be dropped.

It’s been reported that Mueller is probing whether Trump’s interactions with Comey amounted to obstruction.

Per the Journal:

Mr. Barr’s memo is peppered with strongly worded phrases about the peril he sees in Mr. Mueller’s reading of the law, as he understood it. He described Mr. Mueller’s approach as “grossly irresponsible” with “potentially disastrous implications” for the executive branch. He also wrote: “Mueller should not be permitted to demand that the President submit to interrogation about alleged obstruction.”

The Justice Department told the Journal that Barr had written the memo “on his own initiative.” Rosenstein, who had been overseeing the probe when Barr sent him the memo, said the document “had no impact on the investigation.”

President Trump announced his intention earlier this month to nominate Barr as attorney general. Barr, who supported Trump during his presidential campaign, previously served as attorney general under President George H.W. Bush.

If confirmed, he will replace acting Attorney General Matthew Whitaker, who has filled the role since Jeff Sessions’ resignation last month.