This paper sheds new light on the determination of environmental policies in majoritarian federal electoral systems such as the U.S., and derives implications for the environmental federalism debate on whether the national or local government should have authority over environmental policies. In majoritarian systems, where the legislature consists of geographically distinct electoral districts, the majority party (at either the national or the state level) favors its own home districts; depending on the location of polluting industries and the associated pollution damages, the majority party may therefore impose sub-optimally high or low pollution taxes due to a majority bias. We show that majority bias can influence the social-welfare ranking of alternative government policies and, in some cases, may actually bring distortionary policies closer to the first-best solution.