Should-Read: The opposing argument, of course, is that a president who misuses his pardon power should be sanctioned by impeachment. Of course, that would mean that a president who can maintain the confidence of half the House or one third of the Senate could become a dictator. Thus I think Zunger's side has the best of this argument:
Yonatan Zunger: What can be Pardoned?: "This [Arpaio] pardon is now being challenged in court as being unconstitutional... https://medium.com/@yonatanzunger/what-can-be-pardoned-bd113749898a
...The argument is clearly outlined in a letter sent by a group of lawyers to the Criminal Division....
For due process and judicial review to function, courts must be able to restrain government officials. Due process requires that, when a government official is found by a court to be violating individuals’ constitutional rights, the court can issue effective relief… ordering the official to cease this unconstitutional conduct. And for an injunction to be effective, there must be a penalty for violation of the injunction—principally, contempt of court....
Contempt of court is not like an ordinary criminal charge: it is the mechanism by which court orders are actually enforced. This is the same issue raised by the “Trial Balloon” case, where Customs and Border Patrol (acting on Trump’s orders) refused to obey court orders: if the courts have no method to enforce their orders that doesn’t rely on the Executive Branch’s assistance and cooperation, then the Executive Branch is above the law, and neither the President nor anyone acting on his behalf can be stopped by any law. If Trump can legally pardon Arpaio, then he has the power not just to pardon criminal offenses, but to render any court order null and void—civil orders, discovery orders, restraining orders—simply by removing any penalty for violating them. He would have a completely unrestrained power over the courts...
