Enterprise Library 3.0 introduced the Policy Injection Application Block (PIAB) to solve the problem of implementation concerns leaking into the services -- a problem not only in service-oriented design, but in object-oriented design as well.
To leverage the PIAB, you must have control over how your objects are instantiated. With service frameworks like WCF that abstract object instantiation away from the developer, this creates a problem when trying to integrate the PIAB. However, WCF provides a variety of extensibility points through behaviors.
In the February issue of MSDN Magazine, Hugh Ang and David San Filippo show you how to leverage custom WCF behaviors in order to apply PIAB at the WCF service point without requiring additional code.