I think we may be arguing in circles. The Clean Air Act gives the EPA the authority to grant the State the ability to set their own standards. It does not requi

I think we may be arguing in circles. The Clean Air Act gives the EPA the authority to grant the State the ability to set their own standards. It does not require the EPA allow States to set their own standards. If the question is whether the States have the authority to set fuel standards absent Federal approval, I think the Commerce clause stipulates that they cannot, neither directly nor effectively. The Supremacy clause of the Constitution means that EPA standards will preempt the State standards if the EPA says they should. My original point is that’s probably a good thing overall, because what’s true for vehicle efficiency standards would be true for innumerable other goods which we want to be able to sell anywhere in the country under a single standardized set of [safety, environment, labeling, packaging, warranty, liability, supply chain, and labor] regulations.