Who is affected and how:

• Automakers and vehicle suppliers: The prohibition on technology-forcing tailpipe rules limits EPA’s ability to set standards that effectively require particular drivetrains (e.g., battery electric vehicles). Automakers may alter product planning, reduce or delay EV investments in response to a federal constraint, and shift fleet-mix strategies to emphasize internal combustion engines or other technologies. Supply-chain decisions (batteries, electric motors, fuel systems) could be affected by greater regulatory uncertainty.

• New-vehicle buyers and consumers: Consumers may see broader continued availability of internal combustion engine vehicles and potentially slower federal-driven shifts toward vehicle electrification. Price, choice, and vehicle feature availability could change depending on manufacturer responses.

• Environmental and public health outcomes: If the change results in weaker or less technology-specific emissions standards, projected reductions in greenhouse gases and some pollutant co-benefits could be diminished, with potential negative consequences for air quality and health. The exact environmental impact depends on how EPA replaces or revises regulations within the two-year window and how states respond.

• EPA and federal regulators: The agency must revise its regulations within two years, requiring rulemaking, legal review, and administrative action. This imposes a compliance burden on EPA and may invite litigation over interpretation and implementation. The statutory amendment narrows EPA’s regulatory discretion under the Clean Air Act regarding tailpipe standards.

• States and state programs: The bill does not explicitly address state standards (including California’s waiver authority). States pursuing more stringent standards may face new federal constraints or legal uncertainty, potentially triggering legal challenges or separate actions by states.

• Dealers and aftermarket businesses: Vehicle inventories, stocking decisions, and dealer incentives could shift depending on manufacturer offerings and demand changes produced by regulatory signals.

Net effect: The legislation constrains federal authority to push specific propulsion technologies through tailpipe regulation, likely preserving broader availability of conventional-engine vehicles in the near term, while shifting regulatory, planning, and legal activity to EPA, industry, and possibly state governments. The environmental and market outcomes will depend on how EPA revises regulations, how automakers respond, and whether states take parallel actions.