"I just noticed that the VW web site states that Diesel (TDI) engines are NOT available in California, Maine, Vermont, New York and Massachusetts..."This is how I understand it; please correct me if I'm wrong!
It has to do with those states having strict(er) laws about diesel fuel and emissions. Because diesel has traditionally been heavily-polluting, these states are throttling the supply of passenger diesel-powered cars. I think it also affects Mercedes-Benz, and whoever else sells passenger diesels.
Next year, all diesel fuel sold in California is required by law to be of the ultra low-sulfur variety, which is lower-polluting, and therefore VW will be allowed to sell TDIs again.
Or something like that.