This chapter concludes this book by exploring the success, limitations and future global outlook of the pan-European UNECE environmental regime including challenges for future non-UNECE accession, drawing upon an unparalleled seventy years of experience supporting international law on transboundary watercourses and freshwater ecosystems. From the key findings, this book draws a series of overarching and cross-cutting insights into the rising impact and contribution of the UNECE regime to the clarification and development of international law, which also raises outstanding areas for future research. It explores questions of legitimacy as the UNECE regime moves towards its new global role. This research bears in mind the importance of distinguishing policy arguments for signing up to the UNECE regime with legal arguments. The problem arising from a legal perspective is to ask whether it is good legally when international courts or international institutions endorse a regionally specific detailed regime as global law? This analysis demonstrates that the UNECE environmental instruments were never intended to be geographically exclusive and have also already been co-developed by non-UNECE countries for some time. This research supports the UNECE’s endeavour to embrace a global role but cautions that a strong mandate from non-UNECE countries must drive this process.

The latest Sustainable Development Goal (SDG) reporting exercise demonstrated the wide spectrum of arrangements and shortcomings for transboundary cooperation at the river basin level in the UNECE regime, from basins with comprehensive legal frameworks to basins with no agreement at all. Transboundary water cooperation works best when there is a basin-level agreement and these agreements should be more detailed than regional or global treaties but must incorporate these rules and principles. This chapter identifies how the UNECE water regime contributes to transboundary water cooperation at the basin level through the development of basin agreements, river basin organisations and less formal cooperative arrangements. It identifies how the UNECE has supported implementation and compliance with the UNECE regime and international law at basin and national level and the involvement of non-state actors. It examines a range of basin arrangements including those with no agreement, like the Western Bug, or basins with advanced frameworks like the Danube and Sava. It also analyses the value of the UNECE regime in basins already subject to EU environmental law – seeking to understand the specific contribution of the UNECE vis-à-vis the EU law and discusses why EU states have demonstrated interest in the UNECE regime.