1. Introduction

International organizations are a relatively new phenomenon in international relations. They first emerged during the nineteenth century and became ever-more important over the course of the twentieth century. Today, international organizations are involved in nearly all issue areas – from A, as in Arms Control, to Z, as in Zones of Fishing. General purpose international organizations such as the United Nations (UN) or the European Union (EU) cover many different topics, while task-specific organizations such as the International Labour Organization (ILO) or the European Space Agency (ESA) specialize in specific issue areas. Some international organizations, like the UN, have a near universal membership. Others restrict membership on the basis of criteria such as geography, economy, culture or religion; examples include the EU, the African Union (AU), the Organization of the Petroleum Exporting Countries (OPEC), the Organisation for Economic Co-operation and Development (OECD) and the Organization of Islamic Cooperation (OIC). All these international organizations contribute to establishing and implementing norms and rules which guide the management of transnational, cross-border problems, such as climate change, the proliferation of weapons of mass destruction or international terrorism. It is thus no exaggeration to say that it is difficult to understand contemporary world politics without referring to international organizations.