This Article explores potential impacts of the U.S. Supreme Court’s decision in Loper Bright Enterprises v. Raimondo on the Federal Energy Regulatory Commission (FERC), focusing on FERC’s efforts to mandate long-term interregional transmission planning. FERC has justified many transmission planning rules under the “just and reasonable” standard in §206 of the Federal Power Act, and its interpretation of this standard was entitled to Chevron deference. Loper Bright and the judiciary’s larger shift toward skepticism of agency action and disregard for agency expertise endangers bodies like FERC that rely on broad delegations to apply their old enabling statutes to new and pressing problems. The resulting uncertainty threatens to render state climate goals impossible, raise electricity prices, exacerbate blackouts, and impede grid upgrades that are necessary for a 21st-century power system.