The subpoenas typically asked the firms -- Google Inc., America Online, Microsoft and Yahoo -- to turn over every inquiry typed into their search engines during a given week, while allowing the firms to delete information identifying the individuals who conducted those searches.

While insisting that their compliance did not compromise user privacy, three of the firms complied to some degree. Only spokesmen for Google, the world’s most popular search engine, said they continue to resist the demand.

“We complied on a limited basis and did not provide any personally identifiable information,” Yahoo spokeswoman Mary Osako told The Washington Post. “In our opinion this is not a privacy issue.”

Indeed, privacy advocates told the Post they would not object to government subpoenas of Web search histories in criminal cases where a specific individual is suspected of a crime. But fishing expeditions as broad as this constitute “the government’s nose under the search engine’s tent,” warns Marc Rotenberg of the Electronic Privacy Information Center, a nonprofit privacy group. “Once we cross this line it will be difficult to turn back.”

“The real issue here is, is Google being deputized to spy on us?” asks Richard Smith, a Boston-based software engineer who has written about the Internet age. “What will the next case be? It’s a terrible precedent.”

Indeed. “Slippery slope” and “camel’s nose” arguments would seem even more tedious, were it not for how often they’re proved right. Many a constitutional outrage that was once tolerated “only in emergencies” has now become so commonplace as to draw little notice. How many younger Americans today realize that in the 1960s drivers licenses carried no photographs and were not shown to anyone but traffic officers; airline passengers and their bags were not searched, and the friendly stewardess would help a traveling hunter find room in the overhead bin for his fully functional high-powered rifle?

Wouldn’t police and prosecutors find their jobs made easier if they could cross-index lists of people who searched marijuana cultivation Web sites against those with higher-than-usual electric bills or credit card charges for hydroponics equipment? They might well want to search the homes of people who “Google” for online information on machine guns -- even if the researcher turns out to be a kid writing a school report.

And once we’ve started down that road, wouldn’t it be merely prudent for the FBI to keep a close eye on those who visit Web sites that seem to espouse obstructive methods of protest against the Iraq war, or in favor of “animal liberation,” or any other radical cause du jour?

Not only would officials be tempted to so use a new Internet monitoring power -- they might be judged derelict in their duty if they failed to do so. (Look how they were criticized for not doing enough about Arabs attending flight schools, they might earnestly explain.)

Note that the case in hand involves an effort by the Justice Department to resurrect a 1998 “Child Online Protection Act” which may have been intended to shield children from Internet pornography, but the enforcement of which was already blocked by the high court, ruling the federals failed to show the law’s criminal penalties would protect children without unduly limiting the freedoms of adults.

As the government prepares for a new trial in that case in Philadelphia this fall, Justice Department officials coo that they merely need the baseline Web search data to establish a “factual record” buttressing their contention that the 1998 law would be more effective than filtering software in preventing children from accessing online porn.

They’re warned that the proposed law would limit our freedoms, and they decide to bolster their case by infringing our privacy? What next -- a little vacation for opposing counsel in a dog kennel in Guantanamo?

Of course easy access to pornography by children is a concern -- though it is a strictly parental concern, not one in which the federal government has any authorization to meddle.

This creates, in parents, a ready market for screening and filtering technologies which will be developed -- which are already being developed -- far faster and more efficiently by private industry than could ever be anticipated from some lumbering Washington bureaucracy.

Just as the chance that junior might find dad’s copies of Penthouse under the bed never justified government bureaucrats “running” the background of every subscriber, so must we jealously guard today our freedom to use the Internet as we see fit, without fear that Big Brother is watching.

“Their demand for information overreaches,” protests Google associate general counsel Nicole Wong. “We had lengthy discussions with them to try to resolve this, but we were not able to and we intend to resist their motion vigorously.”

Good.