The District Court and Magistrate Judge ruled the Government must make a probable cause showing that the location records will provide evidence of a crime. Buchanan argues the lesser standard applicable to pen registers and trap and traces, that only a showing that the data is relevant to an ongoing investigation, is necessary. Prosecutors routinely use information obtained from pen registers, trap and traces and cell site locator records to get wiretaps.

At issue in the Pennsylvania case is "historical" cell phone location records. Buchanan argues it's no different than pen registers and trap and traces because it doesn't intercept the voice. Scholars and many other judges have disagreed, saying when you use the cell phone to determine location, it's like a tracking device. The law requires probable cause for tracking devices.

Here's an article about the controversy. The Amicus Brief (pdf) filed by law professors in the case, argues persuasively in my view that:

Government acquisition of cell-site location information (“CSLI”), whether historical or prospective, constitutes a Fourth Amendment search because it intrudes upon users’ reasonable expectations of privacy.

It can also implicate the First Amendment.

As the Magistrate Judge persuasively presented, CSLI may disclose to law enforcement agents that a cell phone user has attended an Alcoholics Anonymous meeting, sought AIDS treatment, or visited an abortion clinic. See Lenihan Order, 534 F. Supp. 2d at 586 & n.6. CSLI may divulge when and where a user gave confession, viewed an X-rated movie, or protested at a political rally. Knowledge that the government could keep track of such information could easily inhibit valuable and constitutionally protected activities.

So why is the Obama Justice Department, through this Bush-holdover U.S. Attorney who refuses to tender her resignation, taking the position that so many say violates the Fourth Amendment?

These aren't NSA orders we're talking about, but orders in routine criminal cases, often drug cases. The applications and orders are sealed as are the orders to cell phone providers. So unless there is an Indictment, no one even knows they were entered or their movements were tracked.

The Government also uses cell site locator records to get real time information. They can ping the phone and find out you are home. They can direct law enforcement to your location so they know where to establish physical surveillance on you.

It should be a no-brainer that when the Government seeks information about your location from your cell phone they need a warrant based on probable cause, not some boiler-plate statement to the judge that the information is relevant to an ongoing investigation.

The lower court's opinion in the Pennsylvania case is here (pdf). The Obama Justice Department briefs, filed by Buchanan, are here (pdf) and here (pdf). The second was filed just last week.

The first court order on the topic, by Magistrate Judge Jamie Orenstein (a former federal prosecutor) in 2005 in the Southern District of New York, refusing the government's request for cell site locator records without a showing of probable cause is here.