The making, application and enforcement of international law are no longer confined to national states. A rapidly growing number of non-state actors also play a role. These actors are rather heterogeneous. Their role, representativeness and thus legitimacy greatly differ. However, they have in common that they challenge basic assumptions on which international law and international relations have been based. These challenges include the gradual replacement of traditional diplomatic relations by networks of national government officials interacting with one another across borders. These government networks are in turn often embedded in larger 'global policy networks' that involve a wide variety of non-state actors - NGOs, corporations, individual experts, and intergovernmental organizations. New forms of accountability for these non-state actors are also emerging.