Saint Paul encourages the members of the church in Corinth to mend their ways. That’s good advice for anyone wishing to avoid the expanded latitude new F.B.I. guidelines will give agents to search databases, go through household trash, and use surveillance teams to scrutinize the lives of people who have attracted their attention. Privacy advocates warn that such authority raises the potential for abuse.

The new rules add to several measures taken over the past decade to give agents more leeway in their search for signs of criminal or terrorist activity. Michael German, a former F.B.I. agent who is now a lawyer for the American Civil Liberties Union, said that it was unwise to ease restrictions on agents’ power to use potentially intrusive techniques, especially if they lacked a firm reason to suspect someone of wrongdoing.

“Claiming additional authorities to investigate people only further raises the potential for abuse,” German said, pointing to complaints about the F.B.I.’s surveillance of domestic political advocacy groups and mosques and to an inspector general’s findings in 2007 that the bureau had frequently misused “national security letters,” which allow agents to obtain information like phone records without a court order.

Valerie E. Caproni, the F.B.I. general counsel, said the bureau, which does not need permission to alter its manual so long as the rules remain within broad guidelines issued by the U.S. attorney general, had weighed the risks and the benefits of each change.

“Every one of these has been carefully looked at and considered against the backdrop of why do the employees need to be able to do it, what are the possible risks, and what are the controls,” she said, portraying the modifications to the rules as “more like fine-tuning than major changes.”

Source: An article by Charlie Savage for the New York Times