Block namespace creation for users inside project

For security reasons we don’t want our users to be able to create namespaces inside their project.
Unfortunatly we can’t find a way to block this feature…

Namespace creation is a clusterRole called create-ns bound to users by clusterRoleBindings of the same name. Deleting thoses ressources makes no difference as Rancher auto-recreates them immediately.

Any help would be greatly appreciated
Thx in advance