Forbes: EPAs proposed tough new standards for power-plant emissions of greenhouse gasses opens the door to new state or regional cap-and-trade systems to limit carbon discharges. It is less clear whether it would go the next step and permit states to impose their own carbon tax. The proposed EPA rules, which Brookings senior fellow Barry Rabe describes as climate federalism, seem to acknowledge the demiseat least for nowof a single federal solution to the climate problem. Instead, it grants states...