The use of the autopen, a device that reproduces signatures and is ubiquitous in government and business, is ordinarily uncontroversial. There is no power to undo a pardon in the Constitution or case law.

Donald Trump says Joe Biden's last-minutes pardons via autopen are null and void. But what is an autopen? And what does it mean for pardons?

President Trump has said "many" pardons issued by Joe Biden are void because the former president signed them with "autopen" - a device which reproduces a person's signature - rather than by hand.Trump did not provide evidence for his claim - which was posted on Truth Social.