Daru allows the prisoner to choose between fleeing the law and joining some nomads, or selecting the road to the prison. He gives the man this choice because, although the man's "stupid crime revolted him," handing him over to the authorities "is contrary to honor."
Albert Camus's short story "The Guest" exemplifies Absurdism. Like Camus, Daru is a Frenchman who was born in Algeria, a North African colony of France, but his parents are French and have lived on the continent. This story exemplifies Camus's belief in Absurdism.
[Camus] thought that life had no meaning, that nothing exists that could ever be a source of meaning, and hence there is something deeply absurd about the human quest to find meaning. [https://plato.stanford.edu/entries/camus/]
The individual conflicts with this absurdity, but there is no resolution to the conflict. Because he is not really part of the police, Daru does not feel it is his responsibility to turn the prisoner over to the authorities. If he does turn the prisoner over, he risks attack by the relatives and/or friends of this prisoner, a dangerous position to be in because he is some distance from Balducci and the police. Besides, the area is his home; it is where he was born: "Everywhere else, he felt exiled." When Daru returns to his schoolhouse, he finds written on the blackboard a message threatening him for having turned over their brother. Daru realizes that "[I]n this vast landscape he had loved so much, he was alone." He feels the alienation that comes from acting in an absurd world.