Allowed Template(s) for Parent

[Soma]

I have a template that only can have a certain template as parent. But if I have pages set up, I still can change the parent pages template to use another template, it doesn't throw an error.

[ryan]

This options are primarily for guiding the direction of newly created pages. They don't affect pages already in the system.  So when you choose "require this parent" that means "require this parent when creating a page that uses this template".