On Feb. 7, 1978, as Dow Chemical Co. went about its business of making everything from pesticides to aspirin in Midland, Mich., a small plane equipped with an aerial camera made six unannounced passes overhead and photographed every inch of Dow's sprawling plant.

The snoop was the Environmental Protection Agency, getting evidence without a warrant for an air pollution case against the nation's No. 2 chemical giant.

Dow immediately sought refuge in a federal court and a principle more often popularly associated with accused dope dealers, moonshiners and other assorted criminal suspects -- the Fourth Amendment freedom from "unreasonable searches and seizures." Dow said the photos "captured" sensitive trade secrets.

In an improbable marriage of causes, Dow is scheduled to appear before the Supreme Court Tuesday to defend the right of privacy from government intrusion, in tandem with a convicted Santa Clara, Calif., marijuana-grower whose back yard was photographed by police from the air.

"All the forces of a technological age . . . operate to narrow the area of privacy and facilitate intrusions into it," Dow said in its brief, quoting a 1965 treatise on privacy.

"In modern terms, the capacity to maintain and support this enclave of private life marks the difference between a democratic and totalitarian society." Dow is not the only unconventional champion of the Bill of Rights these days. Real estate developers are invoking the Fifth Amendment's protections for private property to stop local governments from zoning land as "open space."

Political action committees use the First Amendment to fight limits on campaign spending. The National Rifle Association looks to the Fourth as a bulwark against unwarranted searches for guns, as well as the Second for its guarantee of the right to bear arms.

This adds a new verse to an old gospel preached by the American Civil Liberties Union: the Constitution is for everyone. The ACLU is on Dow's side, as is the U.S. Chamber of Commerce, Mountain States Legal Foundation and other conservative groups fighting government surveillance.

"Just as we defend the Nazis when they want to exercise freedom of speech, just as we defend the right to a fair criminal trial even when the defendant appears to have committed a heinous crime, we say that if Dow Chemical's rights aren't protected, neither are yours or mine," said Art Spitzer, legal director of the ACLU's Washington office.

Behind the cases of Dow and "pot" grower Dante Ciraolo is the question of what constitutes privacy in a high-tech world, where binoculars, listening devices and planes can take the government through walls and over fences.

In recent years, the Supreme Court and lower courts have sanctioned technologically enhanced law enforcement by land and at sea, with binoculars, telescopes, beepers, breathalyzers and more. But Dow and Ciraolo represent its first opportunity to rule on whether Fourth Amendment privacy protections reach into the air.

Resolving this modern social problem by referring to a 200-year-old Bill of Rights unleashes inevitable ideological debates.

"The Founders could not possibly have been thinking about a world in which there are airplanes," the ACLU's Bert Neuborne said. "I don't think Attorney General Edwin Meese has thought through the implications of his doctrine of the Founders' original intent. A strict application really cripples modern law enforcement."

The government argues in Dow that an entire layer of privacy vanished with the advent of air travel. "That privacy has been lost to the public, and it cannot be recaptured by reading the Fourth Amendment to impose special limitations upon the viewing of government officials."

Although many citizens may not know it, aerial photography by the government is a fact of life. The U.S. Geological Survey has photographed most of the country for mapmaking, the U.S. Forest Service to monitor vegetation changes, the Army Corps of Engineers for flood control, the Pentagon for strategic defense.

EPA officials said their use of aerial photography has burgeoned along with environmental consciousness, particularly in the search for toxic waste.

All federal agencies have access to the photos, and officials say their ability to enforce federal laws would be hampered without them.

"If there's an area of the United States that hasn't been photographed, it's because we can't get the clouds out of the way," said Vernard Webb, director of the EPA's Environmental Photographic Interpretation Center, which has a staff of 50 pilots, photographers and other specialists.

"They the sites being photographed don't own the airspace, so why would we need a warrant?" Webb asked.

"Even flying for pleasure, you have to fly over something. When you're in airspace, it's yours," he said.

The government emphasizes that EPA used only a 35-mm camera, and film no more sensitive than Kodak Ektachrome slides to photograph Dow. EPA magnified the pictures twofold.

But Dow complained that they could have been blown up 20 times, revealing pipes no thicker than a man's thumb. Because much of Dow's chemical processing takes place outside of buildings, the configuration of pipes constitutes a trade secret, and could be worth millions of dollars if slipped into the wrong hands, company officials said.

"A threat to Dow's privacy threatens its very existence and integrity as a scientific, technological and researched-based company," Dow said in its brief.

So many corporations felt the same that the Chamber of Commerce entered the case on Dow's side, representing petroleum and iron and steel operations, which also substantially take place outside, and the auto industry, which conducts road tests on outdoor tracks.

But EPA's Webb said the danger has been overblown.

"There are already laws on the books that require EPA to protect confidential business information. If one of the secrets of someone's trade is to pollute the environment, I doubt that they'd have much success in keeping it secret."

The Supreme Court has over the decades defined privacy largely through the eyes of those exercising it -- the government needs a warrant to go where a person has "a reasonable expectation of privacy." But recent exceptions allow officials to look without a warrant into some normally private areas from public spots, and, under a 1984 ruling, to enter an "open field," even one privately owned and ringed with "no trespassing" signs.

Through Dow and Ciraolo, the Court could also declare an "open skies" exception.

Dow was charged in 1978 with violating the Clean Air Act and thereby threatening public health because two power plants were spewing particulate matter, dense smoke and sulfur dioxide, the main ingredient of acid rain, into the atmosphere.

After inspecting the plant, with Dow's cooperation, EPA officials asked permission to take photographs to document whether Dow had room to install pollution control equipment, a request Dow refused. Dow said EPA officials discussed obtaining a warrant, and then without notice took to the air to do what they were barred from doing on the ground.

Dow had secured its plant with a multimillion-dollar system of fences, patrolling guards, motion-detectors -- all indicating, in the company's view, that Dow expected privacy.

Also, Dow worked with the Federal Aviation Administration to trace suspicious planes flying over its plant.

The government conceded that Dow has privacy rights from the ground, but asserted that there is no "reasonable expectation of privacy" from the air for a 2,000-acre site.

"It's not an open field from the ground but it is from the air?" remarked Dow's attorney Jane Gootee.

"If you look from one perspective it's a horse, if you look down it's a cow. They can't have their cake and eat it, too."

Similarly, the Santa Clara police saw no marijuana in the back yard of Ciraolo's home because it was shielded by a 10-foot-high fence. They conceded that they would have needed a warrant to scale the fence or even to peek through it.

Ciraolo's lawyers argued that the police effectively "jumped" the fence with the help of the airplane, violating his right to privacy in his home and back yard.

The police argue, however, that Ciraolo "could not have rationally believed" his garden of 70 cannabis plants would not be viewed from the air.

Moreover, they said, the court would have allowed them to view Ciraolo's garden without a warrant from a nearby hill, had one existed. So why not from an airplane in public airspace?

The lower courts offer only conflicting guidance on the issue. In Dow, the U.S. District Court ruled with Dow, but the U.S. Court of Appeals in Cincinnati reversed, siding with the EPA. In Ciraolo, the California Supreme Court ruled that the evidence gleaned from the air was inadmissible.

Neither Dow nor Ciraolo expect much material gain from the cases. Dow settled the EPA pollution charges in a 1982 consent order, agreeing to install emission controls and to pay $500,000 in fines to Michigan and the United States. Ciraolo has served his jail time and paid a $750 fine.

The real stakes, they say, are the principles. Dow wants EPA to hand over the pictures and to take no more, in the name of privacy; Ciraolo wants his felony conviction erased as unconstitutional.

"Is this the case on which the fate of the republic is going to turn? The answer is no," the ACLU's Neuborne said of the Dow case. "Flyovers are an incremental loss of privacy in a world in which privacy is shrinking every day. I'm sympathetic with the view that you have to draw the line on technologically enhanced snooping.

"But we're a society that already tolerates vast amounts of government snooping and this is an increment."