In a legal battle between a Californian tribe and the state’s water agencies, experts are seeing a turning point in the history of United States water rights, potentially affecting how water is controlled across the entire country. In November of last year, the Supreme Court declined to hear a case that the Agua Caliente Band of Cahuilla Indians, concerned about the effects of climate change and the quality of the water in the aquifer, brought against the Coachella Valley Water District and the Desert Water Agency. This Supreme Court decision left standing a Ninth Circuit ruling, which established—for the first time—the principle that tribes have priority over their reservations’ groundwater.