Wireless Mesh Networks (WMNs) have recently attracted increasing attention and deployment as a promising low-cost approach to provide last-mile high-speed Internet access at metropolitan scale. Security and privacy issues are of most concern in pushing the success of WMNs for their wide deployment and for supporting service-oriented applications. Due to the intrinsically open and distributed nature of WMNs, it is essential to enforce network access control to cope with both free riders and malicious attackers. Dynamic access to WMNs should be subject to successful user authentication based on the properly pre-established trust between users and the network operator; otherwise, network access should be prohibited.