This paper highlights a disjunct between geomorphic concepts of braided riverbed lateral boundaries and legal definitions used to decide these boundaries in New Zealand—a country that hosts over 150 gravel-bed braided rivers. These powerful morphodynamic systems are prone to recurrent bar reworking and channel shift. When parts of the riverbed are temporarily abandoned by active channels, they are vulnerable to land use intensification. Associated flood protection measures that often follow intensification constrict the rivers' capacity to adjust to ever-changing flows of water and sediment. Despite the rivers' vulnerability and constriction, New Zealand law defines braided rivers in a way that limits local councils' authority to manage land use within the braidplain. This paper explores the relationship between the law and science of braided rivers, demonstrating how legislative reforms underway in 2023 express the ways in which particular social processes play out in the landscape.