How widely is the United States government using cellphones to pinpoint the locations or track the movements of Americans, or people living on American soil?

In November 2007, the American Civil Liberties Union filed a Freedom of Information Act request with the Department of Justice seeking records related to such tracking practices. The Justice Department did not provide the requested information, the ACLU said.

And so Tuesday, the ACLU and the Electronic Frontier Foundation filed a lawsuit in federal court to try to force the Justice Deaprtment to comply.

In a news release, the ACLU said that the information about how and how often the government tracks Americans using cellphones needs to come to light to determine if the efforts are unconstitutional.

The ACLU said it filed the initial data request after media reports showed that some government officials were claiming not to require “probable cause” of a crime being committed before getting court permission to do real-time tracking of cell phones.

Specifically, the civil-liberties group said, it based its request on an article I wrote in December 2005. That article discussed the discomfort that some courts were feeling about the government’s use of cellphone tracking technology. In that story, legal officials said that some judges wanted government investigators to show probable cause.

As I noted in that article, the government can get such information from cellular operators, like Verizon Wireless and AT&T, which generally know the location of their subscribers within about 300 feet when their phones are turned on.

Such tracking information could be critical, prosecutors have said, to finding suspects or corroborating their whereabouts. And prosecutors have said that there already were legal protections in place to prevent law enforcement from tracking at will, without cause.

But the ACLU and the EFF, an organization that focuses on Internet and technology law, said that the public has an “overwhelming interest” in finding out how often the government is seeking to track Americans and why. If the information is withheld, it distances Americans from the decision-making process about how and when tracking should be permitted, the legal advocates said.

“Further delays will allow important privacy polices to be developed behind closed doors,” said David L. Sobel, senior counsel to the EFF.