The Qpid project has two ACL implementations. An initial version of ACLs was added to the Java Broker for M2.1 that uses XML configuration. For M4 a new format was designed to be implemented by both C++ and Java brokers. M4 release includes the initial C++ implementation and M5 is expected to include the Java implementation.
The specifications for each of the ACL formats are linked here:
v1 XML ACLs (Java Broker Only)
v2 All brokers
To aid users in defining their ACLs we have a user guide for each of the ACL formats.