The U.S. National Research Council released its much-anticipated study of emissions standards Thursday, and its recommendations are a major disappointment to automakers. The NRC study backed the rights of individual states to set their own tough vehicle pollution standards independently of the federal Environmental Protection Agency, following the lead of California.

California implemented pollution regulation before the federal government, and has been granted the authority to continue setting its own standards. Other states can choose between federal standards and California's tougher rules.

The NRC found California's approach to be both scientifically valid, and necessary because of persistent pollution problems in some parts of the state. California in 2004 approved the world's most stringent rules to reduce greenhouse gas emissions, and automakers have been lobbying hard to restrict their adoption by other states.