If you're interested in the debate over cell site location information, a recently published comment by Christopher Fox in the Seton Hall Law Review will provide you with excellent background and analysis of the legal issues. Here's an excerpt:
Part II of this Comment will explain the process cell phones use for sending and receiving calls, messages, and information, as well as how CSLI data is computed to produce an approximate location of a cell phone. Part III will provide the relevant Fourth Amendment jurisprudence, explain the language and protections provided under the SCA, and examine the Third Circuit’s interpretation and application of the statute to a § 2703(d) order request. Part IV will argue that the Third Circuit’s cursory analysis of historic CSLI in light of the relevant Fourth Amendment jurisprudence was incorrect, and will highlight the resulting failure to set forth guidelines for § 2703(d) order requests that would end the application of discrepant standards. Finally, Part V will propose an amendment to the statute that will eliminate the current discrepancy and clarify the requirements for compelled disclosure of historic CSLI.