The 9th Circuit Court of Appeals Nov. 18 put the brakes on an FBI and police technique to eavesdrop on conversations inside vehicles equipped with OnStar or similar dashboard computing systems, according to press reports.

The decision is binding only in California, Oregon, Nevada, Washington, Hawaii and other states that fall within the 9th Circuit's jurisdiction. No other appeals courts appear to have ruled on the matter.

The case arose from a 2001 FBI surveillance operation in Las Vegas, in which agents obtained a court order compelling a telematics company to secretly activate the stolen vehicle recovery feature in a customer's car.

The feature, designed to listen in on car thieves as they cruise around in a stolen auto, turns on a dashboard microphone and pipes conversations out over a cell phone connection – normally to the company's response center, but in this case to an FBI listening post.

The court reasoned the FBI is not legally entitled to remotely activate the system and secretly use it to snoop on passengers, because doing so would render it inoperable during an emergency.

In a 2-1 ruling, the majority wrote that "the company could not assist the FBI without disabling the system in the monitored car" and said a district judge was wrong to have granted the FBI its request for surreptitious monitoring.

Commenting to various press outlets, David Sobel, an attorney with the Electronic Privacy Information Center, said the ruling is not a victory for privacy.

"Although the bottom line is that the surveillance order was rejected, the real effect of it is that this kind of monitoring is permissible as long it does not interfere with the service," he said. "It underscores the fact that it's becoming increasingly difficult to escape the reach of surveillance capabilities."