Stupid question, but could this guy end up in some sort of legal trouble? He's obviously a hero and saved the lives of everyone on board, but it's still illegal to fly a plane while unqualified, right?
But seriously most likely there are laws that allow you do things in emergency and not be prosecuted. In the UK it is called the doctrine of necessity. The example given was that only a doctor is allowed to give an order to use “prescription only” medicine. But in emergency situations where there is no doctor and you need to save a life, then it would be ok to do by anybody else as long as he has at least some idea what he is doing.