President Biden’s pardon for his son not only allowed him to escape consequences from his current convictions, but likely for any crimes he might have committed in the past 11 years.

That sweeping amnesty is raising awkward historical comparisons and sharp questions about the use of presidential clemency.

It also has inflamed a debate about who deserves mercy and for what, while underscoring the Biden family’s concerns about Hunter Biden’s vulnerability to prosecution related to his foreign business activities. Experts searched for an apt comparison, finding some similarities to the pardons granted by Gerald R. Ford to Richard M. Nixon; Andrew Johnson to former Confederate soldiers; George H.W. Bush to Iran-contra figures; and to those issued to more distant family members by President Bill Clinton and by Donald J. Trump during his first term.

Yet, none of those pardons seemed to hit as close to home for the presidents who issued them, nor did they cover as broad a range of activity over as long a period of time, experts said.

“It is extraordinarily hazardous to use the pardon power in a case where the person is an intimate of the president,” said Aziz Z. Huq, a professor at the University of Chicago Law School.

Mr. Huq, who warned against Mr. Trump pardoning himself at the end of his first term, said President Biden’s pardon of his son “really does strike at the rule of law.”

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