What would have to happen

[xajj4791]

for any Trump pardons to be over turned?

I think his ability to pardon should be frozen during any impeachment process but I have no idea what the Constitution says about this nor what if anything SCOTUS has said (or other federal courts).

[drray23]

1. its absolute, not subject to review .

it can not be overturned. The only exception is that the president cant pardon crimes to stop his impeachment.

[MineralMan]

2. There is no mechanism for doing that.

Presidential pardons are absolute and final.

[The Velveteen Ocelot]

3. The power of a president to grant pardons is almost absolute, and pardons can't be revoked.

The Constitution is easily located on the Internet, but here's the relevant clause, Article II, Sec. 2, Clause 1: "...he shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment." The president can't grant a pardon for impeachment or for state crimes, and most legal scholars think he can't pardon himself. But otherwise the courts can't prevent or revoke a pardon.