Almost a year to the day after new Bureau of Indian Affairs (BIA) residential and commercial leasing regulations became effective, the Agua Caliente Band of the Cahuilla Indians has decided to press enforcement of these regulations. The regulations, which became effective on January 4, 2013, added a new section, 25 CFR section 162.017, asserting that states may not impose any fee, tax assessment, levy or other charge on permanent improvements installed on, on activities conducted under, or on leasehold or possessory interests created by leases issued under Part 162. In July, the Ninth Circuit Court of Appeals in Confederated Tribes of Chehalis v. Thurston County Board of Equalization ratified at least a component of the new BIA leasing regulations, holding that state imposition of taxes on permanent improvements was preempted by federal law. Now, the Agua Caliente Band of the Cahuilla Indians has recently filed suit seeking to invalidate Riverside County’s possessory interest taxes and permanent improvement taxes imposed on lessees of reservation lands. The Tribe claims that the tax revenues collected by Riverside County do not directly benefit services on the reservation, and that the Tribe would seek to impose taxes to provide needed services. They rely, in part, on the BIA leasing regulations to support their federal law preemption claim to invalidate the County’s tax and to enjoin any further possessory interest taxation by the County on the reservation. The outcome of this case may provide further clarity on the scope of the BIA leasing regulation and federal preemption.