Editors' Summary: As environmental regulation at the federal level has grown increasingly burdensome on states and industry, nearly half of the states, mainly in the South and intermountain West, have responded by preventing their own environmental agencies from promulgating environmental regulations that are more stringent than federal baselines. The author examines many of these restrictions on state regulation, and discusses their causes and potential effects. The author concludes that these states' abdication of their freedom to legislate and regulate innovatively is a strong indicator that in the absense of strong federal regulation, many states would not be likely to regulate the environment to the degree the federal government currently does.