But technology began to pose obstacles in the 1980s, as old-fashioned telephone networks were giving way to digital switching systems that could also transmit information. Suddenly some wiretaps had to become virtual, using "packet sniffing" programs that spy on the splintered packets of data that make up network traffic.
Congress passed CALEA in 1994, requiring telecom carriers to ensure that their networks left it relatively easy for law enforcement to set wiretaps. The law applied to landline and cell phone networks but essentially exempted the Internet.
Of course, at the time, federal officials were advocating use of the Clipper Chip to ensure that bad guys couldn't hide by encrypting their online traffic.
The FBI also was developing Carnivore, a program that agents could tailor to grab specific e-mails and other Internet communications defined in a court order. (The FBI eventually dropped Carnivore in favor of commercial software; frequent cooperation from Internet service providers often made the technology unnecessary anyway.)
And all the while the NSA was harvesting the fruits of a system called Echelon, intercepting millions of international telephone calls and feeding them into the agency's humungous maw for analysis.
Justifiably or not, each of these steps unsettled privacy activists. And it is that unease that colors the current fight over expanding CALEA's reach to new services such as Voice over Internet Protocol (VoIP) by 2007. The FCC says the move is critical because converting voice calls into data packets essentially replaces the old phone system. VoIP services are expected to attain some 4 million U.S. subscribers by the end of this year.
"CALEA in a sense is the culmination of where we've been," said Barry Steinhardt, director of the technology and liberty program at the American Civil Liberties Union. "Now the communications network is built to be wiretap-ready, so you don't need Carnivore anymore. It's just intrinsic to the system."
Clipper Chip objectors a decade ago contended that in addition to being an onerous demand, the technology could be foiled, rendering it pointless.
Similarly, critics of expanding CALEA to broadband networks say the cost of rewiring - estimated as high as $7 billion for universities alone - is excessive. Those against expanding it to VoIP say it leaves too many holes to be effective.
For example, Internet phone services such as Vonage that can route calls to regular phones will be expected to support CALEA. But "peer-to-peer" VoIP services and instant-messaging programs that carry voice conversations from one computer to another are exempt - at least for now.
"If you take the argument to its extreme, every kind of Internet application, including (file-transfer programs) and Web browsing, is capable of transmitting communications. So where does it end?" said Glenn Manishin, an attorney with Kelley Drye & Warren LLP who has handled telecom regulation cases for companies and consumer groups. "Do they now have to have a back door into every Web browser?"
Plus, overseas services aren't covered by the U.S. law. Nor can it touch any home-grown Internet voice programs that serious criminals could develop.
"For the past two years, law enforcement has been saying, `If we just had CALEA we'd catch all the terrorists,'" said John Morris, director of Internet standards, technology and policy at the Center for Democracy and Technology. "Well, if they're sophisticated enough to evade all of our intelligence capabilities, they'll be sophisticated enough not to use a CALEA-compliant phone service."
CALEA critics also say authorities haven't shown that existing monitoring methods are so weak as to justify costly new back doors for government.
Indeed, while they are not nearly as common as phone surveillance, computer wiretaps have been successful even without the extra assistance CALEA might provide. For example, a 2003 report by the Administrative Office of U.S. Courts explained how surveillance on a DSL high-speed Internet line in Minnesota intercepted 141,420 "computer messages" in three weeks, aiding a racketeering investigation.
If there's one thing widely agreed upon in this debate, it's that Congress could do well to step in.