Location privacy management is an important requirement for location based services. Here we describe the design and implementation of location privacy enforcement mechanisms based on the IETF Geopriv specifications as part a location-based services platform that we previously developed. Our design involves a new and more efficient session-based access validation mechanism. In addition, we evaluate the expressiveness of Geopriv rules for describing a variety of privacy rules. We find a number of limitations and propose some methods for extending the rule notation for addressing these limitations. We conclude with an overview of our prototype implementation.