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 Muellers ongoing Russia investigation.

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

Its not the first time that Barr, who would oversee Muellers investigation as attorney general, has been critical of the probe. He told The Hill last year that leaks from the special counsels team raise questions as to whether there is an agenda. Hes also suggested that Muellers 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.

Its been reported that Mueller is probing whether Trumps interactions with Comey amounted to obstruction.

Per the Journal:

Mr. Barrs memo is peppered with strongly worded phrases about the peril he sees in Mr. Muellers reading of the law, as he understood it. He described Mr. Muellers 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.