New Mexico is notable within the Western U.S. for its network of acequias, irrigation ditches brought by Spanish colonists through which communities of irrigators collectively manage their water resources. This thesis considers acequias as a site of struggle for Mexican-Americans in New Mexico via a case study of the unincorporated South Valley outside Albuquerque. I show how U.S. water law historically acted as a vehicle of dispossession, as New Mexico’s newest sovereigns implemented private property rights in place of traditional Indigenous and Hispano systems, including via the 1923 creation of the Middle Rio Grande Conservancy District encompassing the South Valley. Yet the same legal codes are now being repurposed by acequia irrigators to contest prior dispossessions. Drawing on semi-structured interviews, I attend to organizing among South Valley acequieros in the last two decades to demonstrate an inversion of water law amid a robust social movement centered on these old ditches.