The problem isn't diesel vehicles, fuel and/or biofuels in general, but older vehicles that are significant pollution sources compared to the majority of vehicles in the state, which includes older diesels. It's also limited to a specific portion of southern CA with the worst air quality and highest population density, because diesels are associated w/ greater NOx production, a precursor to smog. Besides, it isn't like ya can't come over and save a bunch of older diesels if ya wanna, just don't forget your wallet. Anyhoo, CARB and the EPA don't pretend to know what's best for the country, just what's best for air quality in this context.
