The Tiburon ridge stretches out in a long golden curve, rocky and bright with wildflowers. To the east, one can see small sailboats cutting fine white lines through the blue-gray stillness of San Francisco Bay. To the west, lit by the sun when the fog burns away, the Golden Gate Bridge spans the whitewater where the bay meets the Pacific.

A fine setting for a house, thought Donald and Bonnie Agins when they bought five acres here in 1968 -- a dream house with a dream view.

But it was also an environmental gem, not just a view but a "viewscape" as the planners would call it later, when they moved to preserve it from development.

Now the property is the focus of a potentially far-reaching showdown before the U.S. Supreme Court that has generated an avalanche of legal briefs rivaled only by the abortion funding controversy. The showdown is between the environmental movement and a growing number of landowners and developers who consider themselves its victims.

The briefs make clear both sides' belief that a decision in favor of the Agins could deal a devastating blow to environmental and land-use planning across the nation. And the case has become a vehicle for those who hope for such a decision and those who fear it.

The Agins hoped to sell four acres of their land for construction of four houses and use the proceeds to finance their own home. Twelve years later, there is still no house here.

After the zoners and planners finished their work, the family would have needed to spend thousands of dollars on environmental impact statements and master plans before they could even apply to build. And approval would still not be a certainty.

Believing the property worthless to them, the Agins sued the city of Tiburon for $2 million in 1975. Tiburon, they argued, effectively took their land and should pay for it.

To environmentalists this was an outrageous proposition which they accurately predicted would be thrown out by the California courts.

They did not, however, expect the Supreme Court to accept the case. Now, as the environmentalists tell it, the future of land use regulation is at stake, not to mention hundreds of millions of dollars in claims by landowners like the Agins around the country.

In the past decade, state after state has enacted programs to preserve open space. They survive only because the courts have generally held that the "public good" -- a pretty view, a park, a wildlife area preserved -- overrides the interests of individual landowners in the affected areas.

But as the environmental movement has grown, so has the class of aggrieved landowners. Many are now demanding compensation for what they believe has been taken from them in the name of the public.

If the landowners win a solid Supreme Court victory in the Agins case, environmentalists, state governments and the U.S. government agree that land use regulation will become, like everything else, too expensive.

California, for example, says it has $350 million worth of Agins-type claims in the courts now. Three other claims pend at the U.S. Supreme Court, awaiting a decision on review:

San Diego Gas and Electric Co. is claiming $3.1 million from the California city for rezoning to open space a property intended for a power plant.

Developers in the state of Washington are seeking compensation from the government of Thurston County for blocking plans to develop 14 acres along Lake Lawrence in order to preserve a feeding ground for bald eagles.

Carl Lange and his family are demanding about $1 million from San Juan County, Wash., for adding their property to a "conservancy inventory" for preservation years after they purchased it.

These protesters and others before them have generally been on the losing side in the courts. The Fifth Amendment to the Constitution forbids the taking of private property for public use "without just compensation." The problem for the landowners has been the definition of a "taking." Over the years, most zoning and land use regulations have been upheld as something other than a taking -- the exercise of police power -- and thus requiring no compensation.

But the Supreme Court has never directly confronted the kind of complicated multitiered zoning and land use programs enacted by states in recent years.

The property owners believe that if ever there was a year for victory, this is it. In December, the Supreme Court ruled that the U.S. government had "taken" the property of a Hawaii developer, Kaiser Aetna Co., by requiring public access to a marina on Oahu developed on private property with private funds.

And then, a month later, in an action that surprised and panicked the environmental movement, the justices agreed to review the Agins case.

"You are now entering Agins Acres," says slender, red-haired Bonnie Agins, as she opens her arms to the spectacular panorama around her. "See what we're fighting for?"

Bonnie and Donald Agins, a dentist, found their Tiburon land 12 years ago, when they decided that, with five children at home, they had outgrown their house in the nearby suburb of Lucas Valley.

"We came up and looked at the property and fell in love with it," Bonnie Agins said as she sat on a flat rock in the midst of the wild yellow grasses.

An architect had walked the open land with the couple, rhapsodizing about its possibilities, and the Agins envisioned just what they wanted: a wood house, maybe solar heated, with lots of glass to catch the views, and a swimming pool.

It was an expensive project, but the Agins had decided how they would pay for it. "The attractive part of this property," she said, "was that we could build our own house and sell the part of the property that we didn't want, to help finance our own house."

They figured they would sell four acres -- one house per acre.

Zoning then permitted just such development. The Agins paid $50,000 for the land and held it for several years, until they felt ready to begin building.

During the same period, municipalities in California came under a state legislative mandate to begin preserving open space. The beauty of the state and its coastline was threatened by its population boom.

The city raised $1.2 million to buy property -- including the Agins' -- along Tiburon Ridge in order to preserve it for open space. But by the time they got around to Agins Acres, the money was exhausted. The city then rezoned the Agins property to a completely new category under an ordinance designed "to protect and preserve open space land as a limited and valuable resource."

The new zoning might still allow the Agins to build one to five units on their five acres. But they estimated that it could cost up to $50,000 in fees to consultants and planners to assess the effect on the view and on the flora and fauna of the Tiburon ridge. And to submit this costly impact statement was no guarantee of approval.

The Agins never submitted a request for their project. After listening to city officials and the advice of their lawyer, they decided there was no chance of approval for the five houses they wanted to build. "It didn't seem to make any sense to go through all that if they told you ahead of time you couldn't," said Donald Agins.

"I think when people want something," he said, "they should be willing to pay for it. They shouldn't expect you to donate your property when they want to acquire open space.

"Maybe the city should have to shorten its sights a little bit and realize they can't have everything they want if they can't pay for it. There's a lot of things I want but can't afford. That's just the way it goes."

Lawyers on the other side are still arguing that the Agins should have sought approval for their project before going to the courts. That they didn't exhaust their remedies could result in Supreme Court disposal of their case without a definitive ruling, many lawyers believe. In oral arguments, the justices seemed surprised and concerned that the remedies had not been exhausted.

Briefs at the Supreme Court in the Agins case represent 15 states, dozens of municipalities, the U.S. government, the National Association of Manufacturers, numerous private-property lawyers and every major environmental organization in the Uniged States.

Their arguments have the fervor not of a dry zoning case but a crusade.

In some environmentalist briefs, the Agins cause is pictured as a mission of greed designed to benefit rich developers and wreck the progress of the environmental movement.

The environmentalists in turn are pictured as selfish elitists, living in comfort and enjoying the scenery at the expense of everyone else. It's "an inversion of the Robin Hood principle," argues Gideon Kanner, the Agins lawyer, in which "a conspicuously wealthy community would enhance its enviable condition at the expense of one of its inhabitants, without paying for what it gets."

"The mechanisms of land use regulation have undergone a revolutionary change in the last decade," Kanner argues. "The notion of yore that construction of improvements on land need only be preceded by compliance with zoning ordinances and building codes and the issuance of a building permit has by now joined such venerable images as the hand-cranked automobile." p

The environmentalists and planners argue that landowners should and do have the power to obtain court invalidations of unfair zoning or land use regulations but should not be allowed to collect damages or compensation.

"We're not dealing with someone getting screwed out of the use of their land and having their money taken away," said Nick Yost, general counsel for the federal government's Council on Environmental Quality. "We're dealing with people ambitious to increase the value of the land way beyond what they paid for it. . ."

"And the fact is that everybody benefits from good planning in a community. Any zoning, any land use planning, restrictions on density, preserving open space -- all these do diminish each owner's conceivable potential, but at the same time they guarantee every property owner that their town will be a nice place to live."