N the spring of 2001, Chief Justice William H. Rehnquist sounded an alarm.

"Technology now permits millions of important and confidential conversations to occur through a vast system of electronic networks," he wrote in a First Amendment case. "These advances, however, raise significant privacy concerns. We are placed in the uncomfortable position of not knowing who might have access to our personal and business e-mails, our medical and financial records, or our cordless and cellular telephone conversations."

From the Vietnam and Watergate era until Sept. 11, 2001, legal protection of privacy rights was moving in only one direction, with judges and legislators across the ideological spectrum working hard to create what is in many ways a new legal right.

"Before 9/11, the American concern with invasion of privacy was growing," said Rodney A. Smolla, a law professor at the University of Richmond. "The law of privacy was poised to absorb and reflect some of the public concern. It was about to become the new civil right."

Sept. 11 changed everything, and last week those changes came into sharper focus, suggesting that any comprehensive rethinking of the right to privacy will have to wait. On Monday, two federal appeals courts endorsed vastly expanded government intrusions into the private affairs of Americans, finding privacy interests less compelling than those of rooting out terrorists and child pornographers.

The Pentagon also attracted considerable attention this month for a proposed database of unprecedented scale to help in government antiterrorism efforts. It would collect every sort of information imaginable, including student grades, Internet activity and medical histories. The USA Patriot Act, passed in October 2001, also altered the balance between privacy and government power in countless ways.

Public opposition to greater government surveillance has been muted, even as many people continue to voice concerns about the commercial use of data about themselves. That dichotomy is a little hard to explain, given that intrusion by the government can be life-altering while most businesses can do little more than annoy people with phone calls at dinner time.

The answer, it appears, is that many people believe the government will invade only someone else's privacy. Privacy for me, they seem to be saying, but not for thee.

Recent legal developments have in many ways mirrored these attitudes.

In the battle between consumers and business interests, consumers are winning, said Susan Crawford, a Washington lawyer and an expert in privacy law. But in the battle between citizens and law enforcement, she argued, citizens are losing. The public, it seems, is pleased with both results.

Public opinion polls taken immediately after Sept. 11 as well as more recent surveys indicate substantial public support for domestic security measures like wiretaps approved by secret courts, informants recruited from the ranks of delivery personnel and government surveillance at rallies and in churches and mosques. Yet, national surveys consistently show that consumers are concerned about how commercial information about them is used, said Joel Winston, associate director for financial practices at the Federal Trade Commission.

What exactly these consumers fear is hard to say.

"Privacy is a totally overused and poorly understood term," said Diane Zimmerman, a law professor at New York University.

At bottom, privacy may be about an almost metaphysical sense of vulnerability, akin to the fear in some cultures of having one's photograph taken.

INDEED, the talk turns abstract pretty fast when people are asked what a right to privacy is meant to protect.

"It is about a sense of tranquillity, a sense of autonomy," said Floyd Abrams, the constitutional lawyer.

But metaphysical vulnerability, Mr. Abrams was quick to add, starts to seem less oppressive if the alternative is life-and-death vulnerability, and recent court decisions and legislation reflect that calculation.

In the commercial realm, too, the government is now more concerned with concrete harms.

"What most consumers care about is not an abstract concept but actual injury," Mr. Winston of the trade commission said. "They care about unwarranted intrusions like telemarketing, to someone stealing your identity, to someone using your credit information improperly."

Still, the essential paradox in the post-Sept. 11 era is that people seem willing to accept government intrusions but not commercial ones, even though the government's power is enormous and often wielded in secret, while consumers retain substantial control over their commercial information.

In the commercial arena, "you can always opt out," said Jane Kirtley, a professor of law and media ethics at the University of Minnesota. "In the commercial private sector we really do have a certain amount of choice. In terms of government surveillance, we really do not."

She added: "The private sector can't garnish your wages, can't take your child away, can't arrest you. The government can do all those things."

The government's power was vividly illustrated in the two federal appeals court rulings last week.

On Monday, a special federal appeals court, the United States Foreign Intelligence Surveillance Court of Review, issued its first decision ever, granting the Justice Department broad new powers to use wiretaps obtained for intelligence operations in criminal cases. It reversed a lower court's decision that had limited those powers out of concern for citizens' privacy.

For 20 years, other court decisions and Justice Department policy had erected a wall between the department's intelligence and criminal arms. In its reversal, the special appeals court relied in part on the Patriot Act, but it also said the wall had never been required in the first place.

"This is a giant step forward," Attorney General John Ashcroft said. "This revolutionizes our ability to investigate terrorists and prosecute terrorist acts."

ALSO on Monday, the United States Court of Appeals for the Eighth Circuit, based in St. Louis, held that the police could obtain e-mail messages of an accused child pornographer by faxing a warrant to Yahoo, the Internet service, and relying on Yahoo's technicians to produce the materials. The case turned on whether the technicians could in effect be deputized by the government.

But the courts' actions are nothing, critics said, compared with the Total Information Awareness program of the Pentagon's Defense Advanced Research Projects Agency. The office plans to construct, according to materials posted on its Web site, "ultra-large all-source information repositories." They will include, the site says, "associated privacy protection technologies."

That is small comfort, said Ms. Crawford, the Washington lawyer.

"What people are really worried about is that someone not have a fine-grained picture of their life," she said.

But they worry differently depending on who is looking. "There is now a dramatic split, almost a schizophrenia, in society," Professor Smolla of the University of Richmond said. "There is no diminution in trying to address privacy rights against the media, in commercial settings, in property rights, in business. But we all see that there is a dramatic change in our attitude toward government intrusions."