The ‘National Vision’ of the Bush Administration with regard to homeland security aimed to ‘prevent the entry of terrorists and the instruments of terror while facilitating the legal flow of people, goods, and services’. The unilateral approach taken by the United States and the extraterritorial character of its homeland security measures have resulted in severe conflicts at the transatlantic level. What is puzzling is that despite the societal, political and legal divergences, the EU-US cooperation on homeland security did not slow down, but to the contrary managed to avoid deadlocks and became even more dynamic. The major objective of this research is therefore to understand how to avoid deadlocks in the process of policy-making even despite diverging approaches, ideas, etc. This thesis is an exploratory study of the EU-US homeland security cooperation, with a particular focus on the negotiations of the Passenger Name Records Agreements. The answer offered in this research is twofold. I argue that the shift towards networks and new forms of governance which they stimulate (i.e. soft law instruments) were the reasons why potential deadlocks in transatlantic policy-making were avoided. The basic assumption I make in this research is that the existence of conflict and cooperation in transatlantic homeland security cannot be explained without abandoning the realist assumption that states are unitary actors and the only ones capable of making decisions. Furthermore, I argue that the shift towards networks and the processes within networks were not apolitical. This provides some insights into the instances of conflicts. Following Deborah Stone, the process of policy making in this research is understood as ‘a struggle over ideas’. I argue that in case of transatlantic homeland security this struggle took place within networks which are political bodies in the sense that decisions about their functioning and evolution are politically motivated and impact the overall relationship. Therefore, I introduce the concept of ‘network politics’ with reference to the process whereby members of a network attempt to impact the policy process and outcomes through promoting their own ideas. It is through the prism of the network politics that both deadlocks and enhanced decision making capacities can be better understood. In my exploration of transatlantic governance and network politics I focus on three elements: membership, centrality of actors and the role of bureaucrats.