ABSTRACT
This chapter gives an understanding on how Defence subjects are addressed in public law and what methodology is best suited to investigate such research topics. From an international perspective on the one hand, most studies focus mainly on institutional aspects. Each institution related to the Defence area is considered independently. Comparison is often made between different organizations. As an example, the history and development of NATO is analysed among its contribution to European Defence. The most relevant part of the complexity lies on interactions between NATO and the European Common Security and Defence Policy, as underlined in Article 7 of Treaty on European Union. From an International Public Law point of view, most of the studies tackle this matter by focusing mainly on military external operations analysis. It is key to distinguish in these studies difference between legitimacy and legality (refer to Article 51 of UN Charter). On the other hand, from an internal point of view, Defence studies are sprayed in different fields. Constitutional Law mostly describes the leading role of the president. Decision power is concentrated on his hands. French constitutional reform (2008) leads Parliament to discuss more than ever, even if no vote is required. As a counter example, in the UK, Westminster Parliament has refused an operation suggested by the prime minister (Syria, 2013).
