Some people simply have too much time on their hands.
Interesting issue: the Democrat judge issues a decision that Trump’s pardon is invalid, and orders that Arpaio be incarcerated. Trump’s Justice Department (I know, with Sessions it’s unlikely but let’s say he actually grows a pair for the sake of this hypothetical) issues an opinion that the Judge’s order is invalid and in violation of the separation of powers in the Constitution. What will law enforcement do?