We've recently discovered that the setting in SharePoint Admin that sets "Allowing non-owners to invite new users" to "disallowed" for a site collection means only users that have never had access to the SharePoint Site. We thought it meant new users to the site\library. Existing users with read and contribute rights (non-owners) can still share anything they want and break inheritance on the libraries.

Please give us a way to stop sharing entirely for ALL users or at least for users that are not site owners.