One of the big challenges for the European Union today lies in finding a common foreign policy for its 27 sovereign member states with their divided interests, experiences and traditions. New objectives set requirements on the Union to develop and intensify its military ability. The European Union´s view on when military force can be utilized sets concepts like sovereignty and intervention in focus. Can sovereignty be limited and if so can an intervention be justified? How did the Union argue regarding its participation in the intervention in Afghanistan, 2001? The Just War Theory gives the essay a normative framework against which to assess the Union´s view and guidelines for the use of military capabilities. An idea and ideology analysis examines the relevant documents and materials, and furthermore places them in their social context with the help of a critical discourse. The involvement in Afghanistan 2001 serves as a practical example of the Union´s foreign policy in matters of military force and its use. The European Union is shown to follow the Just War Theory and its criteria regarding sovereignty and just interventions. The practical definition adopted in Afghanistan also seems consistent with the theory´s framework.