Can a president un-pardon someone for a crime for which they were previously pardoned?

For example, suppose Bush in 2000 had wanted to go after Mark Rich, who had been pardoned by Clinton. If Clinton can use his Article II powers to issue the pardon, can't Bush, once president, use those same Article II powers to revoke the pardon?

Double jeopardy says you can't be tried twice for the same crime, but a new trial would be needed - absent the presidential pardon, they are still guilty and would be required to serve the rest of their sentence (or whatever).

If Obama wins this election, can he reverse last-minute Bush pardons? (Not that I think he would - I just wonder if he could, legally.)

You were probably looking for the opinion of an expert on this, but in lieu of that you can have mine.

Pardons can't be reversed either by the president that granted the pardon or by a subsequent president.

My opinion is based on the idea that the constitution doesn't describe an undo pardon power and as such the president doesn't have one.

In addition, after Ford pardoned Nixon there was a lot of talk about ways to get around the pardon. All the powers that be at the time seemed resigned to the idea that the pardon couldn't be undone or gotten around in some way. If there had been a legal mechanism to get around the pardon I think it would have surfaced then.

It's called vigilante justice. All you need is a noose, a tree, and an angry mob. Let's see a presidential pardon undo THAT.

I do believe once they are pardoned they can not be reversed. Clinton did more than pardon Rich. He also pardoned those Puerto Rico terrorists to get the votes for his wife in NY.