President Trump on Friday declared all orders and documents signed by his predecessor with an autopen to be “terminated, and of no further force or effect,” setting in motion an unprecedented legal debate with potentially far-reaching consequences.

Among the orders that would be abrogated if Mr. Trump’s declaration survives the inevitable legal challenges are numerous pardons, as well as high-profile executive actions involving reproductive rights, climate policy, and tech regulation.

Individuals reported to have received pardons signed with the autopen include Mr. Biden’s son Hunter Biden; the former director of the National Institute of Allergy and Infectious Diseases, Anthony Fauci; and the former chairman of the Joint Chiefs of Staff, General Mark Milley.

In his Truth Social posting announcing the move, Mr. Trump claimed that 92 percent of all documents bearing President Biden’s signature were in fact signed with the autopen.

“The Autopen is not allowed to be used if approval is not specifically given by the President of the United States,” Mr. Trump wrote, claiming that “Radical Left Lunatics” around Mr. Biden operated the device “illegally” and without his knowledge.

“Joe Biden was not involved in the Autopen process and, if he says he was, he will be brought up on charges of perjury,” Mr. Trump wrote.

The claim that 92 percent of documents were signed by autopen comes from a House Oversight Committee report issued this year. The figure was based on an examination of thousands of documents by House staffers, who compared the signatures to known samples from the autopen and Mr. Biden.

However, the study was not reviewed in an independent audit or by outside forensic experts, leading Democrats to dismiss the report as a “political diversion.” They also pointed out that the courts have never invalidated autopen signatures, including those of Presidents Bush and Obama.

While it is generally acknowledged that Mr. Biden used the autopen more than his predecessors, he and his former staff have also maintained that the device was never used without his direct authorization, usually when he was traveling or otherwise unavailable.

The House report produced no direct evidence that White House staffers used the autopen without that authority.

While Mr. Trump has the authority to reverse most of Mr. Biden’s executive orders with his own orders — and has frequently done so — any attempt to invalidate Mr. Biden’s pardons would likely end up before the Supreme Court.

Under Article II of the Constitution, presidential pardons are considered to be final and courts have consistently held that a president cannot cancel or undo a predecessor’s pardon.