Seems that’s the answer to the question. It can be challenged and reversed.
yes but on what grounds?
it might depend on what is said in the pardon Nixon had stepped down from the highest office..hillary not so much..obama? depends on if there are charges and what they are
we are at the point that either the rule of law is upheld or not and if Trump gets one or 2 SC justices the pendulum might swing back to law and order