The Supreme Court, ever preoccupied with fundamental matters, has come to the conclusion that a man's home is his castle but his back yard is just the castle's "curtilage" and enjoys a lot less privacy. So a Mr. Ciraolo, California home-owner and marijuana grower, has lost his case and will go to a dungeon beneath a castle moat, or wherever they send such people in California.

The question was: was the Fourth Amendment protection against unreasonable searches violated from an altitude of 1,000 feet? In the Supreme Court, the home of close calls, reasonable people often differ about the meaning of "reasonable."

The meaning of "curtilage" is clear. It is the area immediately surrounding a home, an area for the intimate activity associated with the privacies of life. Privacy expectations are heightened in this area closely linked to the home.

In 1982, the Santa Barbara police received an anonymous telephone tip that the grass in Ciraolo's backyard was the wrong sort. The police, who take a dim view of such agriculture, wanted a view of Ciraolo's crop. Imagine their frustration when they found the back yard -- sorry, the curtilage -- enclosed by a six-foot outer and 10-foot inner fence.

They could not get a search warrant on the basis of an anonymous tip, but they could get an airplane. They flew over Ciraolo's curtilage and got enough -- a clear view of the marijuana -- to get a warrant. Ciraolo was arrested, convicted and on his way to the Supreme Court.

There, he argued that his Fourth Amendment right of privacy -- regarding unreasonable searches -- was violated by the surveillance from an airplane. He lost. He should have won. Chief Justice Burger, speaking for Justices White, Rehnquist, Stevens and O'Connor, raised sophistry to a new height -- about 1,000 feet.

Ciraolo argued that the government agents would have required a warrant to see from the ground what they saw from the air. If the officers had, without a warrant, used a ladder to peer over his fence, they would have had the ladder knocked out from under them, so to speak.

But Burger's majority made much -- indeed, almost everything -- of this flimsy fact: the police made their observations from within publicly navigable airspace, and any member of the public flying in that airspace could have glanced down and seen what the police saw. Burger also said a 10-foot fence would not shield a marijuana crop from a policeman perched atop a truck or double-deck bus. A curtilage is not excluded from all police observation. Policemen are not required "to shield their eyes when passing by a home on public thoroughfares."

In other words, suppose the police had passed by on a double-deck bus. Suppose all you like. This did not happen.

In 1980, George Brett, the Kansas City Royals third baseman, made 30 errors. He said: ''Suppose those 30 pitches had been balls. Then I would have had no errors." Nice try, George. Nice try, Chief Justice, with that thought about police wandering observantly down public thoroughfares, or happening by on double-deck buses.

Hearing that thought, the four justices who disagreed must have been tempted to make a noise like a truckload of coal sliding down a tin chute. But such is the mutual esteem in which the justices hold each other, or pretend to, that Justice Powell, ever courtly, probably just rolled his eyes heavenward. In his dissent (joined by Brennan, Marshall and Blackmun), he said:

The crucial point about a search is not the physical position of the police. The crucial matter is whether the police action violated an expectation of privacy that was reasonable and constitutionally protected. Obviously, the Constitution does not disable policemen from observing what any member of the public could see. However, the officers in this case were not just ambling observantly. They were swooping over a house -- a particular house -- in a plane obtained for that purpose. It is, to say no more, unconvincing to compare, as the majority does, the threat to privacy from police swooping over a targeted house and the potential loss of privacy from an idle, fleeting glance of a passenger in a commercial airliner.

Life is dotted with minor tragedies, and Ciraolo's loss in the Supreme Court is, as tragedies go, minor indeed. No one disputed that his crop was marijuana. He deserves a spell in that dungeon beneath that moat. But there should be a durance vile for justices who use an argument as weak as the one the majority used.