Barr, 68, served as attorney general under the late President George H.W. Bush in the early 1990s. He now Of Counsel at Kirkland & Ellis LLP.
Barr not only said that an investigation of this would be above-board, he claimed it was necessary in the interest of justice.
After leaving the Justice Department, Barr served as the general counsel and executive vice president of Verizon Communications but retired from the role in 2008.
At the Justice Department, Barr's work ranged from combatting violent crime to investigation the Pan Am 103 bombing. In 1977 he received his law degree from George Washington University before working in the Reagan administration as a member of the White House Domestic Policy department.
Be sure to read Allahpundit's analysis on Barr from yesterday, when the Washington Post profiled him as the man most likely to succeed Sessions.More news: Manchester United have time to get back into top four - Jesse Lingard
Barr also at one point took issue with the political affiliations of those on Mueller's team, telling the Washington Post in July of 2017 that "prosecutors who make political contributions are identifying fairly strongly with a political party".
Barr, however, has loyally supported many of Trump's decisions from the sidelines.
Barr wrote that Comey "crossed a line that is fundamental to the allocation of authority in the Justice Department" in announcing the outcome of the investigation into Hillary Clinton's use of a private email server. But depending on how long the confirmation process takes, it is not clear how much of the investigation would remain by the time a new attorney general takes office.
His answer reportedly surprised then-Sen.
Pres. Trump says he will nominate William Barr to serve as attorney general, calling him "a terrific man, a terrific person". Since serving under George HW Bush, he's spent most of his career as a corporate lawyer, so he's more than familiar with Washington's corridors of power.
Later, he advised corporations on regulatory litigation, according to his biography. Mr. Barr, 68, is a former general counsel and executive vice president of Verizon Communications who works now as a lawyer at the firm of Kirkland & Ellis. A graduate of Columbia University, where he graduated in 1973 with degrees in government and Chinese studies, Barr worked in the Central Intelligence Agency from 1973 to 1977.