E-government is an exciting area for applying information and communication technologies (ICT). ICT can improve the efficiency and effectiveness in the provision and delivery of citizen services. A critical issue for the e-government implementation is the interoperation problem among heterogeneous legacy government systems. In this aspect, the universal system interoperability supported by the XML-based Web service technologies can be a useful component in a holistic e-government infrastructure. A key requirement of the e-government systems is the establishment and the implementation of the right access policy to the government resources. This in turn requires an appropriate mechanism to specify the access rules. Due to the nature of Web service and the specific requirements in the e-government context, we propose that a more powerful and flexible mechanism is required to express the access policy more effectively in a Web services e-government infrastructure.