Desert Water Agency v. Agua Caliente Band of Cahuilla Indians

Issue: (1) Whether the U.S. Court of Appeals for the 9th Circuit's standard for determining whether a federal reserved water right impliedly exists"that the right impliedly exists if the reservation purpose "envisions" the use of water"conflicts with the standard established by the Supreme Court in United States v. New Mexico, which the petitioners contend held that a federal reserved water right impliedly exists only if the reservation of water is "necessary" to accomplish the primary reservation purposes and prevent these purposes from being "entirely defeated"; (2) whether the reserved rights doctrine applies to groundwater; and (3) whether the Agua Caliente Band of Cahuilla Indians has a reserved right in groundwater, and in particular whether the Tribe's claimed reserved right is "necessary" to primary reservation purposes under the New Mexico standard in light of the fact that the Tribe has the right to use groundwater under California law.