Heh yet while the king still lived he was still the source and authority for the law...don't forget being a king involved both religion as well as secular authority. Its something that doesn't really exist now in our society, although I suspect that the nearest thing today is marrage
If your a religious person and you get married then there is a religious aspect to it 'joined together in the sight of god' and the secular aspects to it as well. This was the same when someone became king...except in those days the religious aspect was much more prominent...so someone ruled by the will of god and divine law. So just as if you and your spouse were seperated by great distance for a long time you don't just cease to be married so the king and his authority weren't lost or diminished in the same way. This is importent because in those days king actually lead their armies in battle or were at least on the scene, they were not expected to stay at home whilst their armies were fighting. This would not have happened if they lost their kingship everytime they left the country. When John usurped the throne he broke not only secular law he also broke divine law and there was no legal way to fight those who held the reins of power in those days and if you did you were an outlaw as was Robin Hood.I have to say though that in the real world, forgetting all the mythos around Robin Hood who probably never really existed. Prince John was actually the best thing that happend to this country. He was the King who signed the magna carta which was the beginning of democracy in the west and all the bull about taxes etc was just that bull. The problem was that he was a stay at home king and a norman to boot, so he really wasn't popular with the people don't forget that Britian had been invaded and defeated by the normans less then 200 years previously...most of the rulers were of norman blood and most of the people were of saxon blood and they never even spoke the same languages. The language of the rulers was french while most of the people spoke old english which was mainly saxon and danish with a little french thrown in. King Richard though had mainly English blood though and he was a dashing hero type and so was very popular. Of course in reality he couldn't speak english either and spent very little time in this country whilst John lived here. The difference between the two was that Richard was a man of action who cared about fighting and furthing his own fame and glory wereas John actually cared about the country. The legends of Robin Hood though really spring up from the divide between the ruling classes and the people two different 'races' really sharing the same land.