This book seeks to make a contribution to international politics. Following the literatures on economic and societal globalisation, transnationalisation, constitutionalisation, civilisation and bureaucratic institutionalisation, a new constitutional quality can be observed in the international realm. This quality is constituted by processes of international interaction. It is special since its organisational roots and normative substance cannot be derived from either the modern nation-state or an international organisation. This particular constitutional quality thus lies ‘in between’ (Curtin 1996) different conceptions of a political entity. It entails norms, rules and principles that guide politics and law and that are constituted through social practices. However, with the growing influence of this constitutional quality through a web of treaties within the United Nations (UN), European Union (EU), Mercosur and North American Free Trade Agreement (NAFTA) contexts, and in the light of political and social change on a global scale, the quality is increasingly contested (Koskenniemi 2007). Thus, the reform of the UN system involves a debate that addresses not only the UN institutions but the very future of international law. And, the EU treaties’ periodical update and revisions have, for the first time in five decades, triggered an intensive constitutional debate. Both processes sustain the notion of contested norms, rules and principles in the international realm.