In that case, the pardon's legitimacy might never be tested in court, said Kalt. For a court to rule on the pardon's validity, a federal prosecutor would have to charge Trump with a crime and then Trump would have to raise the pardon as a defense, he said.
COULD THE VICE PRESIDENT TAKE OVER AND PARDON TRUMP?
In a 1974 memorandum, a Justice Department lawyer said President Richard Nixon could not pardon himself but that another option was constitutional: that he temporarily step down, receive a pardon from his vice president and then regain power.
In order to do that, Nixon would have had to invoke the 25th Amendment of the U. S. Constitution, which allows an incapacitated president to temporarily step down.
Nixon ultimately resigned in the face of the Watergate scandal and almost certain impeachment and removal from office. His successor, Gerald Ford, later pardoned Nixon for any federal crimes he committed or might have committed while in office.
It is not clear what Vice President Mike Pence would have to gain from agreeing to pardon Trump, said Corey Brettschneider, a professor of political science at Brown University.