So, pardons can very much apply before conviction or even prosecution. They may not pardon someone for something that hasn’t happened, but as long as there in office when the crime is committed that’s more a technical issue.
https://en.wikipedia.org/wiki/Burdick_v._United_States
After President Gerald Ford left the White House in 1977, close friends said that the President privately justified his pardon of Richard Nixon by carrying in his wallet a portion of the text of the Burdick decision, which stated that a pardon carries an imputation of guilt and that acceptance carries a confession of guilt.[6] Ford made reference to the Burdick decision in his post-pardon written statement furnished to the Judiciary Committee of the United States House of Representatives on October 17, 1974.[7] However, the reference related only to the portion of Burdick that supported the proposition that the Constitution does not limit the pardon power to cases of convicted offenders or even indicted offenders.[7][8]
Is this really the case? Has this specific situation ever been ruled on by the Supreme Court? Burdick v. U.S. doesn't address "pre-pardons" or blanket pardons. Nixon was never prosecuted or tried.
The court ruled they could reject a pardon given before prosecution thus avoiding the need to testify about someone else. It would be a moot point if the pardon was invalid.
https://en.m.wikipedia.org/wiki/Burdick_v._United_States
But that's not the relevant part of Burdock for this thread.
The relevant part is that an (accepted!) pardon does apply before indictment.
no, the president can pardon individuals convicted of a criminal law, which is not at all what you describe here