The common theme of the Research Programme 2003-2006 is Diversity of Legal Systems and Global Order. Under this heading, the Research Programme 2003-2006 will examine the diffusion of public authority over diverse legal systems and examine how these legal systems interact and communicate in the exercise of public authority in the global order. The choice of this research theme is induced by the recognition that public authority is no longer controlled by states. The incessant growth of the interaction and interdependence between states and between markets has resulted in a proliferation of international legal systems and institutions. In an internationalised world, public authority is distributed over a diversity of national and international legal systems. The Research Programme uses the term legal system in a broad way. A legal system consists of a set of principles and rules that guides the behaviour of natural or legal persons and that has its own methods for the making, interpretation and application of the law. Certain legal systems are relatively distinguishable from other legal systems. For instance, national legal systems can be distinguished from and the international legal system due to the differences in law-making and law-enforcement. In other cases the distinctions are more fluid, such as the distinction between EU law and international law or between functional fields such as trade law and environmental law, which share the same method of law-making, but that have their own rules for interpretation, change and application of the law. This Research Programme uses the term legal systems to cover all these forms. Diversity of legal systems is not a new phenomenon in the international legal order. International society has always been highly differentiated in political, cultural and social terms and international law has always lacked unity and homogeneity. However, the diversity, some say fragmentation, we are witnessing now is of a different kind. The traditional horizontal diversity between states has been supplemented with a vertical diversity between national and international legal systems and with diversity between various parts of the international legal order. Political authority is allocated to a wide variety of new international institutions, often in areas that were previously considered unsuitable for international regulation. It has spread across institutions at regional and global levels. It has also spread to institutions established to deal with functional areas such as human rights, international trade and environmental protection. None of the legal systems that make up the global legal order can stand on its own feet and function independently of the others. The protection of public values such as security, welfare and environmental protection depends on interaction between different systems. Likewise, values such as democracy and accountability and the rule of law can no longer be guaranteed by individual states but are dependent on regional and global institutions. This phenomenon has often been described as multi-level governance. In the global order, public authority is exercised through interaction between diverse legal systems. The object of the Research Programme 2003-2006 is to identify, describe and analyse relevant phenomena in order to build both a factual and systematic knowledge concerning the questions of how public authority has become diffused over diverse legal systems and how these legal systems interact and communicate to carry out public authority in the global order.