The Clean Air Act is often heralded as a paragon of cooperative federalism. The Act’s approach to vehicle emissions regulation in particular prescribes a unique partnership between the federal government and the state of California: while all states are bound by federally mandated vehicle emissions requirements, California may set more stringent standards in recognition of its historic role on the leading edge of environmental protection. However, in August 2018, the Environmental Protection Agency proposed not only to roll back the national emissions regulations, but also to revoke California’s ability to set more stringent standards, which include limits on greenhouse gas emissions and zero-emissions vehicle mandates. This revocation, finalized in September 2019, sparked legal challenges and debate on the role of states in environmental protection. The Supreme Court’s recent expansion of the anticommandeering doctrine in Murphy v. National Collegiate Athletic Association may signal increased constraints on federal power over states, which in turn may shed light on the permissibility of the EPA’s action to revoke California’s enhanced regulatory ability. This Note assesses the impact of Murphy on the distinction between permissible preemption and impermissible commandeering of state regulation, then applies that distinction to the vehicle emissions context. Ultimately, this Note argues that Congress and the courts should recognize the value of state involvement in environmental regulation and be wary of discarding the current dual-regulator system for vehicle emissions, owing to both policy and federalism concerns.