An intense public feud erupted on Thursday between President Donald Trump and his one-time ally, billionaire Elon Musk, with an argument about Trump’s massive tax and domestic policy bill raging across social media and in the Oval Office.

Musk’s used his social network X to attack President Donald Trump Thursday by tapping the same tactics he previously used to bash Trump’s political adversaries.

The Justice Department under Democratic and Republican administrations has recognized the use of an autopen to sign legislation and issue pardons for decades. Trump presented no evidence that Biden was unaware of the actions taken in his name, and the president’s absolute pardon power is enshrined in the U.S. Constitution.

The Justice Department is examining pardons issued by Joe Biden in the final days of his presidency amid an investigation into his cognitive health.

President Donald Trump has ordered his administration to investigate former President Joe Biden’s use of an autopen to sign pardons and other documents