In 1976, Attorney General Edward Levi adopted domestic security guidelines to regulate intelligence collection in the United States and to deflect calls for even stronger regulation. In 1983,Attorney General William French Smith revised the Levi guidelines to encourage closer investigation of potential terrorism. He also loosened the rules governing authorization for investigations and their duration. Still, his guidelines, like Levi's, took account of the reality that suspicion of "terrorism," like suspicion of "subversion," could lead to making individuals targets for investigation more because of their beliefs than because of their acts. Smith's guidelines also took account of the reality that potential terrorists were often members of extremist religious organizations and that investigation of terrorism could cross the line separating state and church.¹⁶

In 1986, Congress authorized the FBI to investigate terrorist attacks against Americans that occur outside the United States. Three years later, it added authority for the FBI to make arrests abroad without consent from the host country. Meanwhile, a task force headed by Vice President George H.W. Bush had endorsed a concept already urged by Director of Central Intelligence William Casey-a Counterterrorist Center, where the FBI, the CIA, and other organizations could work together on international terrorism. While it was distinctly a CIA entity, the FBI detailed officials to work at the Center and obtained leads that helped in the capture of persons wanted for trial in the United States.

The strengths that the FBI brought to counterterrorism were nowhere more brilliantly on display than in the case of Pan American Flight 103, bound from London to New York, which blew up over Lockerbie, Scotland, in December 1988, killing 270 people. Initial evidence pointed to the government of Syria and, later, Iran. The Counterterrorist Center reserved judgment on the perpetrators of the attack. Meanwhile, FBI technicians, working with U.K. security services, gathered and analyzed the widely scattered fragments of the airliner. In 1991, with the help of the Counterterrorist Center, they identified one small fragment as part of a timing device-to the technicians, as distinctive as DNA. It was a Libyan device. Together with other evidence, the FBI put together a case pointing conclusively to the Libyan government. Eventually Libya acknowledged its responsibility.¹⁷ Pan Am 103 became a cautionary tale against rushing to judgment in attributing responsibility for a terrorist act. It also showed again how-given a case to solve-the FBI remained capable of extraordinary investigative success.