In recent years, the wireless roaming infrastructure has been deployed in many organizations. The eduroam is one of the wireless roaming infrastructures which realize international roaming by cooperating hierarchically structured user authentication systems. However, the guest user’s IP address assigned is the foreign organizations then the network access of the guest users may be restricted. In this paper, we propose a network access control mechanism which makes users' network access transparently while following the policies of their organizations even when they visit other organizations. We call this feature the policy roaming.