In a second, unanimous ruling involving Duke Energy (nyse: DKE - news - people ), the justices said that before making major modifications to coal-fired power plants, plant owners must have a permit, which would require that the facility be outfitted with anti-pollution controls.

FORBES: Greener Days Ahead?

In April, the group finally got an air permit--the document needed to demonstrate it's complying with federal and state pollution laws--five years after it began the application process.

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