The problem in the story is that the Sheriff of Nottingham hates Robin and he tries to kill him examples: 1- the sheriff asks the village people to tell him where Robin hood is, to come and kill him. 2- the prince wants Robin dead too and he told the sheriff to kill him. 3- the sheriff does a arrows contest because he knows that Robin will come to the contest.
The main problem is that the sheriff and the prince wants to kill Robin Hood and the king is not in England, Robin needs that the king Richard will come back just than he can go back to his house. So for now Robin is fighting the sheriffs men with his men.