From DeveloperWorks, Establish a policy-driven SOA using WebSphere Service Registry and Repository and WebSphere ESB

The WS-Policy specification provides a simple language for expressing
policies supported by Web services. IBM WebSphere Service Registry and Repository
supports loading, changing, and retrieving policy documents, and also supports
using policy attachments to link a given policy with a service. This can then be
used by a run time component, like an Enterprise Service Bus, to retrieve
defined policies for a particular service or operation and act accordingly.
This article shows how you can utilize standard WS-Policy documents stored in a
registry to impact run time behavior in an ESB — and then change that behavior
on the fly with no code changes or redeployment. (IBM WebSphere Developer Technical Journal)

An example of invoking WSRR API from a WebSphere Enterprise Service Bus medation module to use WS-Policy.