The U.S. Supreme Court Monday ruled 6-3 that a unit of Coeur d'Alene Mines Corp. (CDE) received a valid permit from the U.S. Army Corps of Engineers to deposit mining waste in an Alaska lake.

Justice Anthony Kennedy, writing for the majority, said the Army Corps. of Engineers has the authority to issue the permit over the Environmental Protection Agency.

"We conclude that the Corps was the appropriate agency to issue the permit and that the permit is lawful," Kennedy wrote. Though the court acknowledged that the regulations guiding who has authority to grant permits are ambiguous, the majority decided the EPA and the Army Corps had internally divvied up their powers in an appropriate way.

Central to the case was the question of whether the Army Corps properly issued a permit allowing a mining company to release waste by-products into an Alaskan lake. The Ninth Circuit Court of Appeals invalidated the permit in May 2007, citing sections of the Clean Water Act in which the Environmental Protection Agency broadly prohibits the release of newer pollutants.

Coeur Alaska, Inc. applied for a permit at Kensington Gold Mine, located about 45 miles north of Juneau. The permit, issued by the Army Corps of Engineers in 2005, would allow the company to release around 4.5 million tons of mine tailings, a by-product of the gold ore milling process, into nearby Lower Slate Lake over a period of 10 to 15 years.

A trio of environmentalist groups led by the Southeast Alaska Conservation Council sued the Corps and the Forest Service on the grounds that the permit violated sections of the Clean Water Act. Though one section of the act grants the Corps the authority to issue permits for the discharge of "fill material" - a substance that raises a body of water's elevation when added - another sets stricter guidelines, encouraging "where practicable, a standard permitting no discharge of pollutants."

The Supreme Court ruled Monday that this "performance standard" set by the EPA does not apply to the mine waste because it is fill material, a decision Judge Ruth Bader Ginsburg vigorously disputed in her dissent.

"Would a rational legislature order exacting pollution limits, yet call all bets off if the pollutant, discharged into a lake, will raise the water body's elevation?" Ginsburg wrote. "To say the least, I am persuaded, that is not how Congress intended the Clean Water Act to operate."

In an associated case, the plaintiffs also sued the state of Alaska.

The cases are Coeur Alaska Inc. v. Southeast Alaska Conservation Council, 07-984, and Alaska v. Southeast Alaska Conservation Council, 07-990. Justices John Paul Stevens, David Souter and Ruth Bader Ginsburg dissented.

-By Kristina Peterson, Dow Jones Newswires; 202 862-6619; kristina.peterson@dowjones.com

(Mark H. Anderson contributed to this report.)