ARGUS is an authorization framework based on a flexible policy engine. It renders consistent authorization decisions for distributed services (e.g., user interfaces, portals, computing elements, storage elements). The service is based on the XACML standard, and uses authorization policies to determine if a user is allowed or denied to perform a certain action on a particular service. It can be interfaced with different authentication methods, including X509. This is in particular the authentication service of the grid EMI/UMD middleware.
More information can be found at https://twiki.cern.ch/twiki/bin/view/EGEE/AuthorizationFramework#Summary.