In this chapter, I present current debates in IR and legal scholarship on legitimation of the use of force and the application of violence in the war on terror. This chapter serves two functions. For one, reflecting the case selection of this research project as announced in the introduction, I want to place the research interest and envisaged aims in a wider debate on legitimate violence and norm conflicts in the war on terror to argue for the explanatory value of a practice-oriented appraoch on norm transformation.