Rolling back the finding weakens the EPA’s authority to set or tighten greenhouse-gas standards across major emitting sectors, with the most immediate effect being looser emissions requirements for US vehicle manufacturers. Companies planning compliance investments tied to federal GHG rules (fleet targets, powertrain mix, supplier requirements) now face a higher risk of rule changes or pauses while the reversal is implemented. The move is expected to trigger litigation, creating a near-term planning environment where federal requirements could shift again depending on court outcomes and timelines.