Last year the Active Directory team announced that The future of Azure ACS is Azure Active Directory. In following with this direction ACS is not being deployed to all new Azure regions. As a result Service Bus users who use Azure Access Control Service with their Service Bus namespace will not be able to create namespaces in these regions.
Customers are encouraged to use Shared Access Signatures, the default for Service Bus namespaces, going forward. Any customer attempting to create an ACS enabled namespace in a region where ACS is not deployed will receive an error at runtime.