This chapter lays out a novel framework for conceptualising the water-relevant binding and non-binding instruments of the UNECE environmental conventions as one common normative regional environmental regime – an original contribution. In exploring the idea of a single regime, this chapter seeks to overcome a strictly positivist view of international law and understand the relevance of overlapping and/or non-uniform state membership of the UNECE legal instruments. It explores regionalism and regional approaches to international law and examines the relationship of the UNECE regime to international law and other international institutions. It sets out a framework for determining the UNECE regime’s relationship to general international law and other international water treaties – asking whether the regime lex specialis – a theme returned to throughout the remainder of the book. This chapter sets out a framework for exploring the making, implementation and enforcement of international law in the UNECE regime, which is employed throughout the research. This frame contributes to understanding around systemic integration, mutually supportive interpretation and cross-fertilisation in international environmental law and international law relevant to transboundary freshwater ecosystems.