The main reason the strict religious code was able to survive is that anyone who did not follow it was expelled.

The church controls everything in Waknuk.  They determine what is “God’s image” and impose their will on others.  Whenever there is any challenge to their beliefs, they can dismiss it.  People believe them because they have been taught to do so since they were young, and very few people disagree.

Uncle Axel is one of the few people that seems to disagree with the church, but he is not vocal about it.  He does advise David that things are different in some places, and not everything the church says is necessarily right.

Such study as has been possible at a distance, however, does not confirm the view of the Right Wing Church Party that they are the result of unchecked deviation. (ch 6)

There is evidence to suggest that anyone who the church does not like can be easily gotten rid of.  An example of this is David’s real uncle’s story.  He was expelled for a very strange reason.

' The eldest son. The heir. Waknuk should be mine. It would be -- except for this.' He stretched out his long arm, and regarded it for a moment. Then he dropped it and looked at me again. (ch 14)

Gordon was the heir to Waknuk, so it makes sense that someone would want to get rid of him.  His arm was suddenly not the right length?  Might suspicious!  It suggests that power is carefully held by those who have it.