This paper analyses the institutional arrangements for the Waikato and Waipā Rivers in Aotearoa New Zealand to consider how effectively they promote Indigenous rights and the exercise of Māori law and relationships with place. We ask how these arrangements shape power relations and dynamics among different (human and non-human) actors and whether they foster relationality and create the enabling conditions that generate alternatives to modernist ways of governing. After examining the detail of these complex institutional arrangements in a way that exposes their ontological foundations, this paper argues that, despite limitations, particularly in relation to implementation, these arrangements operate to increase Iwi authority and, thus, promote Indigenous rights, and legal and ontological pluralism. This outcome demonstrates a vibrancy and plurality of thinking in relation to new models of law and institutional arrangements in settler-colonial contexts—beyond those grounded in rights of nature—and that there are a variety of pathways towards the realisation of Indigenous rights and authority, and the related promotion of legal and ontological pluralism.