Impeachment != criminal conviction. Impeachment is the Senate removing him from office for high crimes and misdemeanors. Criminal conviction is a jury in a federal or state court finding him guilty of specific offences after a criminal trial.
It may well be the case that a president can't pardon himself for all offences he has committed or may have committed while in office (as Ford pardoned Nixon) and has to ask his successor to do that, but since there's no statute or constitutional provision that specifically bars self-pardons, I don't see how anyone other than the US Supreme Court can say for certain they are or aren't possible.
That's nice.
You are now being needlessly pedantic over a hypothetical that was
clearly stated while rather missing the entire point of said hypothetical.
And no, the Supreme Court isn't the only one that can say for certain - it's pretty much right in what has been quoted and mentioned in this very thread: Where Impeachment is concerned, the President cannot self-pardon. Once impeached, whomever was in office at the time has no more personal say in the matter.
Could the incoming President turn around and then issue a pardon before a proper criminal trial can occur? That has also been answered and that answer is more than a bit unfortunate, despite doing so in a case such as this being ill-advised at best.
Now, going with the stipulation of the original hypothetical: President is Impeached, then convicted (which already fucking alludes to a proper trial) of the same charges that got him Impeached - and likely additional ones - yet for whatever reason refuses to vacate the office ....
He's already been Impeached - he is no longer the President, no matter how much he protests. No one prevented the subsequent trial and he was then convicted of the same crimes that got him Impeached. Since the Impeachment process has stripped him of the office, he cannot pardon himself. The Secret Service now has a choice to make: Allow/help his removal from an office he no longer holds or side with someone with no legitimate claim to the office and resist his removal.
The above is the hypothetical outlined before and now cleaned up and presented as a whole.
The
only way a sitting President could self-pardon is if the charges were unrelated to an impending or in progress Impeachment hearing.
Any other outcome shows that we do not have - and never truly have had - any form of Democracy whatsoever.
Why that had to be spelled out is rather beyond me .... It was right there in the original hypothetical situation .....