Correct, state charges are mostly pardon proof and there is no statute of limitations on murder.
Well, they are entirely Presidential pardon proof, but each state usually has its own pardon provisions. Unlikely to benefit ICE agents as a broad class in any of the places where conflicts over their role are currently prominent, though.
So ... you're saying that this militia as every incentive to overthrow democratie so that they never get prosecuted, right ?
See where this is going ?