With diminished political influence at the White House and on Capitol Hill, environmental groups increasingly and successfully are turning to the courts for help in blocking efforts to relax or scrap environmental protections.

Shortly after assuming power, the Bush administration began to recast federal environmental rules governing utilities, energy producers, manufacturers and logging interests and were challenged by environmentalists. The courts have upheld tough new clean air standards for vehicles and power plants, blocked oil and gas exploration in southern Utah and barred new permits for mountaintop mining and dumping in Appalachia.

Last month, a federal appeals court in California ordered the government to reinstate a Clinton administration rule that will protect nearly 60 million acres of national forests from logging and road construction -- a setback for the administration and timber companies that sought to weaken or kill the measure. The Sierra Club, the Natural Resources Defense Council and other major environmental groups have intervened in litigation several times -- including the logging case -- when the administration refused to defend regulations from legal challenges by industry.

"There clearly is a greater reliance by environmentalists on the courts," said Buck Parker, executive director of the Earthjustice Legal Defense Fund, the nation's largest nonprofit environmental defense practice. "The courts are being viewed as the last line of defense, because the Bush administration cannot be counted on to put up an active defense when industry sues to challenge regulatory actions."

Earthjustice employs 50 lawyers nationwide and spends $18 million a year representing environmental groups in legal actions. Since President Bush assumed office in January 2001, the group's caseload has nearly doubled, Parker said, from an average of 58 cases a year to 100.

Business groups, industry lawyers and some government officials acknowledge that environmentalists have been on a legal hot streak recently, but note that industry representatives have scored important victories of their own. A suit brought by snowmobile manufacturers and sporting organizations helped thwart efforts to phase out snowmobiling in Yellowstone and Grand Teton national parks, while a 2001 Supreme Court ruling weakened Clean Water Act protections for hundreds of thousands of miles of small ponds, streams and wetlands.

"I don't see any type of trend that's going for environmental groups or going against industry groups," said Jeffrey Marks, director of air quality for the National Association of Manufacturers.

Mark Rey, the Interior Department's undersecretary of natural resources and environment, said in an interview that although the volume of court cases has not increased dramatically, environmental groups have been highly effective in choosing their targets.

"I think they've always had a pretty good track record in terms of winning," he said recently. "If you're the plaintiff, you pick your fights. And that's part of what causes us to try to do our jobs right, because we know they'll be watching."

Once a powerful lobbying force with strong ties to officials in the executive branch and in Congress, environmental groups have lost considerable access and influence since the Republican political comeback beginning in 1994. For decades, environmentalists and their allies were successful in playing Congress off the White House to protect hard-won legislative and regulatory gains, and they enjoyed support from Democrats and Republicans.

"Now they have one branch left to turn to to try to see if they can throw up some roadblocks -- and that's the judicial branch," said Richard J. Lazarus, a Georgetown University law professor.

Environmental groups have received sympathetic hearings in the U.S. Court of Appeals for the 9th Circuit in San Francisco, which handles many of the western land use cases and is one of the most liberal circuits in the country. The Court of Appeals for the District of Columbia, which hears many of the Environmental Protection Agency regulatory cases, is more conservative. It ruled against the Clinton administration two-thirds of the time over a seven-year period, according to a study by Jonathan Adler, an assistant law professor at Case Western Reserve University, published in May 2000.

Courts generally defer to federal agencies in controversies over proposed rules, legal experts say. But when a new administration tries to overturn the policy of its predecessor, it must demonstrate that it is not being motivated by political considerations.

"When the court smells something that smacks more of a political decision than a decision really based on the law and the record, then they may be more likely to want to reverse it," said Richard G. Stoll, a Washington lawyer with the firm of Foley & Lardner and former chairman of the American Bar Association's environmental and energy section.

The Bush administration supported a series of Supreme Court and Court of Appeals rulings early in 2001 that paved the way for tough new standards for diesel engine emissions and pollution from power plants, but it bridled at many of the rulings that followed.

In December 2001, a federal judge in Montana temporarily blocked a U.S. Forest Service plan to allow a huge sale of trees charred by fire in Montana and Idaho after environmentalists complained that the government was shortcutting an appeal process and that the clearance would promote runoff that could harm bull trout and other fish. Government officials reached a settlement with environmentalists last February that significantly scaled back the planned sale.

Then in May, Chief U.S. District Judge Charles H. Haden II in West Virginia barred the U.S. Army Corps of Engineers from issuing additional permits allowing coal companies to blast off the tops of mountains to reach rich seams of coal and then dump the rock and waste in valley streams below. Haden's 47-page ruling also rebuked the Bush administration for issuing new rules removing a legal impediment to mining companies that Haden called contrary to the Clean Water Act. The administration and mining companies appealed the ruling.

Environmentalists scored their biggest victory last month, when the 9th Circuit lifted a lower court's injunction and reinstated the Clinton administration's rule designed to protect 58.5 million acres of national forests from logging and road construction. Because the administration refused to defend the new rule on appeal, environmental groups intervened in the case and were granted legal standing by the appellate court.

The 9th Circuit ruled again this month, this time upholding EPA rules requiring small cities, counties and developers to protect waterways from stormwater pollution. Those rules had been challenged by homebuilders, the paper industry and municipalities and defended by environmentalists.

And now, environmental groups are expected to support the efforts of nine northeastern and mid-Atlantic states that have sued the administration over its decision to relax "New Source Review" industrial air pollution standards.

A report prepared last year by Sen. Charles E. Schumer (D-N.Y.) concluded that in nearly a dozen recent environmental cases, the Department of Justice did not appeal adverse court rulings, switched positions mid-case or agreed to an "anti-environmental settlement" with industry plaintiffs. "The reason for this is the administration does not feel bound by the constraints of the laws in their agency actions," said Greg Wetstone of the Natural Resources Defense Council.