Yesterday, we learned that the Acting Attorney General, Sally Yates, had refused to defend President Trump's immigration ban because she "wasn't sure" if it was constitutional. It is, but let's put that argument aside. Yates had three choices. She could defend the EO as written, quit, or stay in her position and defy her boss. She chose the latter.
...And she was, like most people who thumb their nose at their superiors, fired immediately.