WASHINGTON — A divided Supreme Court on Monday upheld the broad power of federal environmental regulators to protect most wetlands from development, even in areas that are dry much of the year.
The decision split the justices three ways and left uncertainty about the reach of the Clean Water Act. But it was a setback for private property advocates who hoped the more conservative court would sharply cut back protections for wetlands.
The case was the first environmental dispute before the court since John G. Roberts Jr. became chief justice, and it highlighted the conservative-liberal divide.
Taking a middle position, Justice Anthony M. Kennedy wrote the pivotal opinion, which appears to provide continued federal control over most wetlands.
At stake were an estimated 300 million acres of sometimes-swampy ground that includes half of Alaska and an area as large as California in the lower 48 states. Since the 1970s, the Army Corps of Engineers has said the owners of this land may not fill or drain it without a permit.
Last year, the court voted to take up a property rights challenge to how the federal government was enforcing the Clean Water Act, which was passed to protect "navigable waters."
John Rapanos, a Michigan developer, was sued and fined by the federal government after he had filled in wetlands on three farm fields about 20 miles from Lake Huron. After a heavy rain, water from the fields flowed into a drainage ditch, and from there to a tiny stream into the lake.
Rapanos and his lawyers maintained that although the law allowed federal authorities to exert environmental control over navigable rivers, bays and lakes, they could not extend it to inland wetlands, such as those on his fields.
Six years ago, the court cut back the government's authority over ponds and isolated wetlands that had no connection to rivers or the sea. In that 5-4 ruling, the justices -- including Kennedy -- said Congress had spoken of protecting the navigable waters of the United States from pollution, and there was no way that pollution from an isolated pond would pollute rivers, bays or lakes.
That decision set the stage for the Rapanos case.
Roberts and Justice Samuel A. Alito Jr., both new to the court in the last year, agreed with Rapanos. The two justices, along with Clarence Thomas, joined an opinion by Justice Antonin Scalia that said only wetlands connected to a steadily flowing stream were protected.
