One issue to consider is that we are using realms to integrate with existing user stores so may not be able to update the remote store: -

• Consider an option to update the remote store if possible.
• If not cache a backlisted user until an admin unlocks that account

Before being implemented this feature will require further discussion, in additional to locking mechanisms for unlocking should also be considered and also the potentional for denail of service type attacks based on locking out the administrators.