Abstract: In Massachusetts v. Environmental Protection Agency (2007), the Supreme Court held, among other things, that the EPA has statutory authority to regulate greenhouse gases under the Clean Air Act, and that the agency cannot decline to do so on political grounds. We analyze the logic of MA v. EPA and its broader implications for administrative law and regulatory policy. We locate MA v. EPA in the context of the Justices' increasing worries about the politicization of administrative expertise, particularly under the Bush administration. The majority's solution for this worry, we suggest, is a kind of expertise-forcing: the Court attempts to ensure that agencies actually do exercise expert judgment, and that they do so free from outside political pressures, even or especially political pressures emanating from the White House or political appointees in the agencies. Whereas a line of caselaw and commentary stemming from Chevron USA Inc. v. Natural Resources Defense Council sees presidential politics and expertise as complementary, expertise-forcing has its roots in an older vision of administrative law, one in which presidential politics and expertise are fundamentally antagonistic. Because the Court subjects the denial of a rulemaking petition to hard look review, we suggest that MA v. EPA is State Farm for a new generation.