Over the last century, international organizations have become central actors in the international system. Today, they are the most important form of long-term institutional co-operation between states on various subject matters. They exist because many of the world’s problems are global or regional in nature. Hence, these problems can only be solved through close co-operation between states in the framework of common international institutions devoted to dealing with these issues. Of course, certain issues can be regulated by bilateral or multilateral treaties, however such a static, limited approach often does not suffice. This is because the most significant contemporary problems tend to be long term and dynamic in nature and require institutionalized resolution mechanisms. Due to the ever-closer web of interdependencies in the global system it is insufficient for general abstract norms alone to regulate these interdependencies and steer them towards common purposes. The sharp increase in number of international organizations since the Second World War (WWII) is clear evidence for an obvious necessity of international co-operation between states within an institutional framework.