Arizona v. New Mexico

Background

The State of Arizona, acting as a large buyer of electricity and on behalf of its citizens, challenged New Mexico’s 1975 Electrical Energy Tax Act. Three Arizona utilities generate power in New Mexico — two investor-owned companies and the Salt River Project, a federal reclamation project and Arizona political subdivision — and sell that electricity only to customers in Arizona over interstate lines. New Mexico’s law imposes a generation tax of 0.4 mill per kilowatt-hour and allows a credit against the state gross receipts tax for electricity consumed inside New Mexico; the Arizona utilities cannot use that credit because their sales occur outside New Mexico.

Reasoning

Arizona asked this Court to hear the case first, arguing the tax discriminates against interstate commerce and violates equal protection, due process, and interstate privileges. New Mexico noted the same constitutional issues were already being litigated by the utilities in New Mexico state court. The Court emphasized that its original, first-instance jurisdiction should be used sparingly when another suitable forum exists. Finding the pending state-court action appropriate, the Court denied Arizona leave to file a bill of complaint here and explained that Arizona could seek review later if the New Mexico Supreme Court rules against it.

Real world impact

The denial moves the constitutional challenge into New Mexico courts, where the utilities must press their claims. The decision does not rule on the tax’s legality. Arizona consumers will only gain relief if the state-court litigation shows the tax raises their electricity rates; otherwise, any further review would follow normal appeal paths.

Dissents or concurrances

Justice Stevens concurred, stressing that Arizona failed to allege the tax affects Arizona consumer rates and therefore consumers lack a sufficient interest to bring the case here; he agreed the Salt River Project can litigate elsewhere and joined the denial.