President Donald Trump has claimed that pardons signed by his predecessor Joe Biden are invalid. His reasoning: They were allegedly signed with an autopen, a signing machine used by the U.S government for decades.

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.

O n Monday, President Donald Trump signaled that he intends to nullify the presidential pardons—issued to those on the House Jan. 6 committee that investigated Trump—executed by President Joe Biden because, he said, they were signed via autopen.