“The Supreme Court has made clear that, subject to the exception for impeachment, the president’s power to grant pardons is “unlimited,” with virtually no oversight or limiting role for Congress.

The president can issue a pardon at any point after a crime is committed and before, during or after criminal proceedings have taken place. The president cannot, however, pardon someone for future crimes. A pardon covers both the offender’s conviction for the crime and the sentence for that crime.”

https://www.scotusblog.com/2021/01/the-supreme-court-and-the-presidents-pardon-power/