In 2008, Argentina’s Supreme Court responded to a collective suit filed four years earlier by ruling against the national government, the city of Buenos Aires and the province of Buenos Aires. The sentence required them to create an environmental clean-up and recovery plan for the Matanza-Riachuelo Basin, a 2240-squarekilometre territory inhabited by over eight million people that covers a part of the city of Buenos Aires along with fourteen districts in the province of Buenos Aires. Yet, eleven years after the sentence, the judges’activism has not led to a resolution of the basin’s complex situation, nor to an elimination of its many conflicts and controversies. Nonetheless, the Supreme Court managed to build a localized juridical order that territorialized law and created a specific institutional regime. The article, based on this emblematic Latin American case, aims at analysing the spatial and territorial dimensions of law, and seeks to contribute to the debates about the impacts of judicialization on environmental public action. On the one hand, the Authors examine the controversies aroused by the basin’s clean-up and the role of law. On the other hand, they confront that role with different hypotheses regarding the spatial and territorial dimensions of law. Ultimately, this article plays a part in a broader geography research program about law in action.