A knowledge base article about CalGroups Recipe for Access Control provided by the UC Berkeley IT Service Hub - Knowledge Portal
Whichever way you handle access requests and approvals (manually or programmatically), you can use CalGroups to centrally store your approved requesters into role groups so that this information may be consumed by your application for access control purposes. In addition, it allows you to automatically de-provision users from your role groups when they leave their employment.
Creating ad hoc groups and manually adding membership
Automating group population and user deprovisioning
The intersection means that a person has to be a member of both groups. Since official groups are programmatically derived and updated, any changes in the official groups you use will be reflected in your access group automatically.