“A federal judge in Arizona will soon consider whether to overturn President Trump’s pardon of former Arizona sheriff Joe Arpaio. The answer to this question has consequences not just for Arpaio and the people he hurt but also for the entire country. And although the conventional legal wisdom has been that a presidential decision to grant a pardon is unreviewable, that is wrong. In this circumstance, Trump’s decision to pardon Arpaio was unconstitutional and should be overturned.”