The FBI says the cell-site information is vital when a cellular phone is used by suspected criminals.
"We recently had a case in a major metropolitan area where kidnappers were using the victim's wireless phone, and the carrier was unable to implement the necessary tap to intercept the conversation," said supervisory agent Barry Smith.
The FBI argues that a court order would continue to be required for any wiretapping. But that argument doesn't sway critics who note that judges routinely grant almost all law enforcement wiretap requests.
In fact, between 1984 and 1994, only seven surveillance requests were denied nationwide, according to U.S. Courts records.
Last year, 1,186 wiretap requests were granted, split almost evenly between federal agencies and local police. A total of 1,094 taps were actually installed, yielding 3,086 arrests.
The FBI has other demands. It wants to know when someone has joined or left a multi-party conversation and to eavesdrop on conference calls even after the target of the tap has put the other parties on hold. This particularly worries privacy groups, XTC who fear it would enable the monitoring of people not named in a court order, without probable cause.
The FBI's smith argues that terrorists could use a conference call to discuss plans to blow up a building. If one caller gets a call-waiting notice and leaves the conference to take the call, he said police should be entitled to listen to both the new call and to what the conference participants are saying in the meantime.
"This is not a hypothetical," Smith adds. "We're seeing two criminally related conversations going on at the same time that we have a wiretap order to hear."
But Dempsey says the potential for unwarranted interception is already great enough. As evidence, he cites Operation Ill Wind, the late 1980s federal investigation that involved taps on 30 Pentagon employees and defense contractors. During the investigation, Dempsey says, federal agents listened to the conversations of up to 6,000 people in the Washington area - many of whom were never suspects but happened to know a contractor or Pentagon worker.
Some in Congress are critical of the FBI's new demands. One of them is Sen. Patrick J. Leahy, the Vermont Democrat who was the chief Senate sponsor of the 1994 Communications Assistance for Law Enforcement Act.
"Delaying implementation of this important law over such a relatively small number of functions, which would only arise in fairly unique and isolated investigatory circumstances, seems extremely short-sighted," he wrote in a letter to Attorney General Janet Reno earlier this year.
For its part, the FCC pledges to give each side a fair hearing.
Because of the complexity of the dispute, the new law is unlikely to take full effect for several more years. And should the FCC return a judgment unacceptable to either side, lawsuits are expected.
Sobel says his group would consider going to court. But he remains optimistic.
"At the very least, this is the only opportunity that the public and the privacy interests have had to have a say in this process," he says.