Hydro-legal geopolitics: Why states join—or reject—global water treaties

This paper introduces the concept of hydro-legal geopolitics to examine why states adopt, reject, or selectively engage with international water law—particularly the 1997 UN Watercourses Convention and the 1992 UNECE Water Convention. Situated within an anarchic global order, the paper argues that legal commitments are shaped less by normative ideals and more by geopolitical dynamics across four axes: power asymmetries, territorial positioning, scalar strategies, and the spatial practices of law. Through case studies of Afghanistan and Iran (Helmand River), Iraq's accession to global frameworks, and reflections on the UK and US, the analysis reveals how historical legacies, domestic politics, and sovereignty concerns mediate treaty behaviour. While international law offers standards like equitable use and no significant harm, its authority is often undermined by strategic calculations and legal instrumentalism. The paper concludes that the effectiveness of global water regimes depends not only on legal design but on their alignment with spatial and geopolitical realities. • Introduces hydro-legal geopolitics as a framework for analysing state engagement with global water treaties. • Shows how power, sovereignty, scale, and identity shape international legal behaviour. • Examines legal strategies of the US, UK, Iraq, Turkey, Iran, and Afghanistan through geopolitical and territorial lenses. • Highlights international law's dual role as normative ideal and strategic tool of spatial governance.