President Donald Trump questioned former President Joe Biden’s autopen-signed pardons, calling them “void," as experts weigh whether courts could rule on the validity of presidential clemency.

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.

President Donald Trump says he believes some pardons issued by President Joe Biden are not valid. On social media, Trump claimed Biden’s use of an autopen voids the pardons, despite legal precedent otherwise.