The D.C. Circuit Court of Appeals rules that U.S. EPA is illegally failing to control ozone pollution — smog — that travels across state lines and contributes to unhealthy air in downwind states. The ruling requires EPA to secure clean air by reducing the pollution emitted by coal-fired power plants and other polluting industries in upwind states — pollution reductions that will save hundreds of lives and prevent hundreds of thousands of asthma attacks every year. The court also rejected arguments by polluting industries and red states that the pollution reductions EPA has already required are too costly.

The U.S. Court of Appeals for the District of Columbia Circuit found that the current national ambient air quality standards for ozone are too weak to protect the environment. The U.S. Environmental Protection Agency will now have to set standards that actually protect forests, as the Clean Air Act requires.