The law of his tribe says that nobody is allowed to visit the Dead Place except to search for metal. However, John, the son of the priest, gets permission to go to the Place of the Gods, even though it is forbidden, simply to look around.
Near the end of the story, John returns and tells his father that he has discovered that the Place of the Gods was actually built by men. He says that his father can "slay" him for breaking the law by entering the Place of the Gods. However, his father replies,
The law is not always the same shape.
The father's statement leads back to the question of whether what John has done is the same as robbery or murder. The law looks at context and intentions. A robber or murder has intentions that mean harm to others. John, however, enters the forbidden city with a pure heart. He does not have any intent to harm. He is simply seeking knowledge, knowledge he now knows can help his people.
John's breaking of the law is similar to someone who ignores a "no trespassing" sign to save a child from a burning building. That person is unlikely to be charged with the crime of trespassing, because the context of his acts show he has done it for a good reason, to help another person live. John's great desire is to help his tribe, so his transgression is forgivable.