Biden’s first wife and daughter were killed in a car crash in 1972, a personal tragedy the president has spoken of often in his political life.
Johnson told the BBC that “there is only so much the executive can do with the legal, with the judiciary and the legal system.”
The White House did not immediately respond to a request for comment. Johnson’s comments were reported as Biden, Johnson and other world leaders were scheduled to meet for the G-7 summit on Friday.
Harry Dunn, 19, was killed after Sacoolas drove on the wrong side of the road in August 2019 and hit him with his car. Under former President Donald Trump in January 2020, the United States rejected calls by the United Kingdom to extradite Sacoolas to face charges of death by dangerous driving.
Johnson had called on Trump to change the US government’s stance on Sacoolas. Dunn’s parents accused Trump of trying to force them to meet Sacoolas in the White House.
Interpol issued a red notice for Sacoolas in May 2020, a notice issued “for fugitives wanted either for prosecution or to serve a sentence”.