Editors' Summary: Federal cap-and-trade legislation is essential if the United States is to reduce greenhouse gas emissions. Five stumbling blocks that the incoming administration and Congress must address in order to get legislation are: the economic rationale for reducing greenhouse gas emissions as part of a clean energy-led economic recovery program; why reductions are best achieved by issuing a capped number of tradable emission permits; how permits will be allocated by the government and any associated revenues disbursed; which government agencies will administer the program; and how America's new plan will move the country toward the promised environmental goals.