Charlie Savage’s story on the FBI’s Domestic Investigations and Operations Guide is a superb follow-up on my questions from yesterday, in which I asked what had happened to the people seemingly targeted through the Najibullah Zazi investigation.

Savage describes how the FBI’s recently revised standards (dated December 16, 2008!!) for investigation have been expanded to allow FBI agents to conduct what are effectively fishing expeditions.

The F.B.I.’s interpretation of those rules was recently made public when it released, in response to a Freedom of Information lawsuit, its “Domestic Investigations and Operations Guide.” The disclosure of the manual has opened the widest window yet onto how agents have been given greater power in the post-Sept. 11 era.

In seeking the revised rules, the bureau said it needed greater flexibility to hunt for would-be terrorists inside the United States. But the manual’s details have alarmed privacy advocates.

One section lays out a low threshold to start investigating a person or group as a potential security threat. Another allows agents to use ethnicity or religion as a factor — as long as it is not the only one — when selecting subjects for scrutiny.

“It raises fundamental questions about whether a domestic intelligence agency can protect civil liberties if they feel they have a right to collect broad personal information about people they don’t even suspect of wrongdoing,” said Mike German, a former F.B.I. agent who now works for the American Civil Liberties Union.

Taking these guidelines, along with the knowledge that the FBI is using Section 215 of the PATRIOT Act to profile people based on their purchase of certain hair care products, and you’ve got investigations into people who have nothing to do with terrorism.