WASHINGTON, United States (AFP) — Donald Trump declared Monday he has annulled preventative pardons issued by former president Joe Biden to members of Congress who angered Trump by investigating the attempt to overturn the 2020 US election.

It was unclear what, if any authority Trump has to void presidential pardons issued by his predecessor.

The Republican claimed that Biden’s signature on the documents had been carried out with a commonly used device known as an autopen and therefore was not valid — without providing evidence either for the autopen or his contention that it would invalidate the signature.

The pardons “are hereby declared void, vacant, and of no further force or effect, because of the fact they were done by Autopen,” Trump posted on his social media account Truth Social.

Biden issued pardons to former senior Republican lawmaker Liz Cheney and other members of the congressional committee that had investigated the January 6, 2021 attack on the Capitol by Trump’s supporters and multiple attempts by Trump to overturn the election in which he lost.

The Biden pardons, issued at the end of his presidency, were effectively a blanket immunity to shield the lawmakers from Trump’s repeated promises that he would take revenge against them if he won the 2024 election.

Trump appeared to acknowledge that his action entered disputed legal territory.

Asked by reporters early Monday whether everything Biden signed with an autopen should be voided, Trump said “I think so. It’s not my decision, that’ll be up to a court.”

But he said the committee members “should fully understand that they are subject to investigation at the highest level.”

Biden also issued preemptive pardons to former Covid pandemic advisor Anthony Fauci, retired general Mark Milley, and — perhaps most controversially — to close family members including his son Hunter. All of them had become public targets of the incoming Republican president.

Trump has repeatedly promised “retribution” against his political opponents and threatened some with criminal prosecution, and Biden said at the time that he could not “in good conscience do nothing.”

On taking office this January, Trump immediately issued multiple pardons to supporters, including to about 1,500 people convicted in the storming of the Capitol building in an attempt to block certification of Biden’s election victory on January 6, 2021.