Trump claimed that Biden's pardon was invalid because Biden used an automated signature machine

On March 17, U.S. President Trump said that former President Joe Biden pardoned members of Congress who investigated the “January 6 insurrection” at the last minute, which was “invalid, vacant, and has no further effect or impact”, suggesting that Trump may be trying to subvert the law and practice of presidential pardons for more than a century. The power of pardon has long been considered one of the most absolute powers possessed by a U.S. president, and courts have been reluctant to impose any restrictions on how pardons can be granted. While Trump acknowledged that the court should ultimately decide on the validity of the pardon, his remarks opened up the possibility that the Justice Department might try to prosecute some of the president’s key political opponents.