ex post facto can be ignored, and a new law of the land passed voiding pardons during 47s term. Because repealing pardons isn't weaponizing the person pardoned's behavior after the fact, it's against Presidential authority, so isn't ex post facto when it comes to the person who's behavior was legally determined to be criminal. Voiding a commutation for cause would be tougher and potential ex post facto, but not a pardon. We can void those without violating our ex post facto standards.
What are the odds the current Supreme Court majority are going to uphold voiding Trump's pardons? Pretty to close to zero.
The only way you could do this would be if you changed the SCOTUS composition through court packing or impeachment or constitutional amendment.
If you wait for the conservative justices to retire and be replaced through death/resignation – by the time that happens, the issue of voiding pardons will likely be mostly irrelevant, because most of the pardonees will be already dead. And that's assuming the political fortune to be able to replace them with justices of a different persuasion, as opposed to just more of the same.
