Reddit reviews Constitutional Cliffhangers: A Legal Guide for Presidents and Their Enemies

One of the chapters of Constitutional Cliffhangers by Brian Kalt covers this scenario and discusses what might lead a president to try self-pardon and what the likely outcomes would be. I recommend it. Tl;dr Kalt suggests that a self-pardon is legal.

I heard a thing on the radio today from a constitutional law professor who said that the president's power to pardon is actually pretty broad, the person being pardoned doesn't have to admit guilt or be convicted, and no explanation has to be given for the pardon.

Also as amazingly stupid as it seems, the president can in fact pardon himself. There could be political repercussions and he could be impeached but he could probably just pardon himself and resign, or resign and let his successor pardon him.

This doesn't put him outside of the purview of state laws though.

https://www.amazon.com/Constitutional-Cliffhangers-Legal-Presidents-Enemies/dp/0300123515/ref=sr_1_1?ie=UTF8&qid=1500669490&sr=8-1

Constitutional Cliffhangars discusses it. Federal level, nearly impossible before impeachment. State level, possible but politically unlikely.