Social Networks, as the main axis of Web 2.0, are creating a number of interesting challenges to the research and standardisation communities. In this paper, we analyse the current and future use of access control policies in Social Networks. Subsequently, two main issues are addressed: the interoperability amongst systems using different policy languages and the lack of elements in the existing policy languages when trying to express Social Networks’ access control. In particular, our approach is based on the use of the XACML standard.