This Note addresses two questions: how does the major questions doctrine affect the way agency lawyers advise policymaking clients, and how does that advice affect agency statutory interpretation and regulation? I first describe the doctrine and discuss normative theories for the role agency lawyers should play in statutory interpretation. Second, I consider the effects the doctrine had during the rulemaking, litigation, and rescission of the Clean Power Plan (CPP), the first ever federal regulation of power plants’ greenhouse-gas emissions. Finally, I identify four major concerns with the doctrine’s ex ante effects on agency statutory interpretation and regulatory processes. These critiques apply broadly, beyond the CPP.