Since the early 1970s a considerable number of multilateral agreements have been concluded in the environmental field that establish a common pattern of institutional arrangements. The purpose of these arrangements is to develop the normative content of the regulatory regime established by each agreement1 and to supervise the states parties’ implementation of and compliance with that regime. These institutional arrangements usually comprise a conference or meeting of the parties (COP, MOP) with decision-making powers, a secretariat, and one or more specialist subsidiary bodies. Such arrangements, because of their ad hoc nature, are not intergovernmental organizations (IGOs) in the traditional sense. On the other hand, as the creatures of treaties, such conferences and meetings of the parties, with their secretariats and subsidiary bodies, add up to more than just diplomatic conferences. Because such arrangements do not constitute traditional IGOs and yet are freestanding and distinct both from the states parties to a particular agreement and from existing IGOs, we have chosen to describe them as “autonomous.” They are also autonomous in the sense that they have their own lawmaking powers and compliance mechanisms.