When a user is disabled in Active Directory, it is not disabled in Rally.
Release: ACNUNL99000-2.0-Agile Central-Unlimited Edition-Perpetual
Currently there is no synchronization for support for when a user is ‘disabled’ in Active Directory to disable the the user in Rally. Users which are disabled in Active Directory will no longer be able to access Rally, however the user will still consume one seat count until the user is manually disabled from the Rally side. Please note this does not impact other WAD functionality where a user is ‘deleted’ in Active Directory will result in the Rally user being ‘Disabled’ NOT Deleted.
When a user is ‘deleted’ from Active Directory if the user attempts to login they will be presented with a white screen. This will be addressed in a future release.