A new lawsuit in Manhattan pitting the U.S. Department of Justice against Google offers a rare glimpse of how determined prosecutors are to defend a process that allows federal agents to gain warrantless access to user records, and how committed the Mountain View, Calif., company is to defending its customers' privacy rights against what it views as illegal requests. The Justice Department's lawsuit, filed April 22 and not disclosed until this article, was sparked by Google's decision to rebuff the FBI's legal demands for confidential user data. It centers on the bureau's controversial use of so-called National Security Letters (NSL),...