Barr himself said that he asked Mueller three times if he failed to indict based upon the silly notion that a sitting President cannot be indicted. Mueller replied no, three times.
You have only the word of proven liar Barr on that.
And as far as that "silly notion" read and learn something for the first time in your pathetic worthless life;
WHAT IS THE JUSTICE DEPARTMENT POLICY?
In 1973, in the midst of the Watergate scandal engulfing President Richard Nixon,
the Justice Department’s Office of Legal Counsel adopted in an internal memo the position that a sitting president cannot be indicted. Nixon resigned in 1974, with the House of Representatives moving toward impeaching him.
“The spectacle of an indicted president still trying to serve as Chief Executive boggles the imagination,” the memo stated.
The department reaffirmed the policy in a 2000 memo, saying court decisions in the intervening years had not changed its conclusion that a sitting president is “constitutionally immune” from indictment and criminal prosecution. It concluded that criminal charges against a president would “violate the constitutional separation of powers” delineating the authority of the executive, legislative and judicial branches of the U.S. government.
“The indictment or criminal prosecution of a sitting President would unconstitutionally undermine the capacity of the executive branch to perform its constitutionally assigned functions,” the memo stated.
The 1973 and 2000 memos are binding on Justice Department employees, including Mueller