Improved access control techniques for distributed messaging systems such as content-based publish/subscribe systems are disclosed. For example, a method for providing access control in a content-based publish/subscribe system, wherein messages are delivered from publishing clients to subscribing clients via a plurality of brokers, includes the following steps/operations. One or more changes to an access control policy are specified. An access control version identifier is associated to the one or more changes. The one or more changes are sent to one or more brokers of the plurality of brokers that have a publishing client or a subscribing client associated therewith that is affected by the one or more changes. The access control version identifier associated with the one or more changes is sent to each of the plurality of brokers.