This volume is the product of a joint effort at the Research Centre of the Hague Academy of International Law. In addition to the introductory reports by the two directors of studies, it assembles the contributions of participants from 15 countries - a group of young lawyers from very diverse legal cultures, who have since embarked on auspicious professional and academic careers. The topic selected, that is, the instruments of international environmental policy, was an expedition into as yet uncharted territory, in the borderland of international economic law and international environmental law. Together we enter what Nobel laureate Douglass C. North has called the ""non-ergodic"" world of environmental regimes, teeming with political and regulatory systems that are frequently subject to unforeseeable technological and natural changes.;This collection of studies is an attempt to address those challenges and to assess them from a legal perspective. Contributions are grouped in three parts : the focus of part I is on the relationship of international trade and the environment; part II deals with the problems of development and the environment; and part III concentrates on the role of specific economic instruments for the implementation of environmental policies.