Government agencies need to transform the way in which they are organized in order to be able to provide better services to their constituents and adapt to changes in legislation. Whereas much e-government research has a technology focus, our goal is to investigate whether business architectures can help governments to recreate agencies to make them robust in dealing with political preferences, and further, whether their adoption can guide the realization of IT-oriented enterprise architectures. In this article the concept of business architecture and its implications are analyzed by investigating the case study of the Dutch Immigration and Naturalization Services. The case demonstrates the mediating role business architectures can play between policy and strategy on the one hand, and enterprise IT architecture on the other. Business architectures help: (1) to define business domains and the events connecting them, and (2) to use principles to integrate the domains and ensure synergies. Business domains can be designed and operated independently, which enable higher levels of adaptability. Our case analyses show that the pluriformity of the political visions, public values, and actors involved and the division of responsibilities complicate the creation of a business architecture.