Kerr on the Fourth Amendment and Cell Phone Location Warrants

Orin Kerr is always worth reading, above all on Fourth Amendment issues.  He has a very interesting piece up tonight on a recent decision by a magistrate judge weighing in on the question of whether the police may obtain a warrant requiring a cell phone company to provide cell phone location information for a person who is subject to an existing arrest warrant.  It's not a national security case, and nothing in it (so far as I can tell from Orin's account) purports to address how the same issue would arise in an intelligence investigation rather than a run-of-the-mill criminal investigation.  But it's easy to see how the issue could arise in a criminal investigation with national security overtones, and hence deserves mention here.