The article analyses the Intergovernmental Science-Policy Platform for Biodiversity and Ecosystem Services (IPBES) through the spectrum of international environmental law. It unpacks the epistemic logics within which IPBES operates and emphasises the normative constructions underlying the mechanism, arguing that IPBES is best understood in light of the rationale and principles of the law of sustainable development. On that basis, the article provides an in-depth discussion of IPBES, and in particular of i) its mandate analysed in light of the principles of the Rio Declaration on Environment and Development, ii) its scope that combines a temporal and spatial perspective to scientific knowledge and iii) its outreach activities seeking to co-operate with a variety of partners, interpreted as an embodiment of the ‘global partnership’ that the Rio Declaration calls for.