A Supreme Court decision has stripped as much as one-fifth of the nation's wetlands of federal protection. The January decision, which ended a legal battle between the U.S. Army Corps of Engineers and a solid waste agency in Illinois, asserted that the Corps has no authority to regulate "isolated" waters unless they are used in interstate commerce.

The fight centered on an abandoned Illinois gravel mine that the Solid Waste Agency of Northern Cook County wanted to turn into a landfill in the mid-'80s. The Corps denied a permit for the project, claiming that the landfill would adversely affect seasonal ponds used by migratory birds, but SWANCC challenged the Corps with a lawsuit in 1994.

The Corps' authority to regulate the use of wetlands stems from the 1972 Clean Water Act and was strengthened by the 1986 Migratory Bird Rule, which gave it jurisdiction over wetlands used as migratory bird habitat. But the current Supreme Court majority has - with the exception of the Bush vs. Gore decision - ruled in favor of states' rights. In a 5-to-4 decision, the court argued that federal government intervention in the SWANCC case was "a significant impingement of the states' traditional and primary power over land and water use."

The fallout from the decision extends far beyond Cook County. It effectively excludes from federal oversight any bodies of water that do not cross state lines, such as isolated ponds, wetlands and the ephemeral playa lakes of the Great Basin. The ruling also raises doubts about the Corps' authority to regulate bodies of water as large as Utah's Great Salt Lake. "There are still a lot of questions about how deep this ruling will go," says Dirk Manskopf of the Sierra Club's Environmental Quality Program, but environmentalists agree that the ruling is a disaster for wetlands protection. In wetlands-rich Wisconsin, as much as 80 percent of the state's wetlands may be excluded from federal protection.