The Wall Street Journal discusses not only the Gorelick memo from March 1995, but the protests from US Attorney Mary Jo White -- whose office prosecuted the 1993 WTC bombing (all quotes from the editorial are in red.
White worried that "Our experience has been that the FBI labels of an investigation as intelligence or law enforcement can be quite arbitrary depending upon the personnel involved and that the most effective way to combat terrorism is with as few labels and walls as possible so that wherever permissible, the right and left hands are communicating" (emphases added).
Thus, White recommended a number of modifications, which were rejected by Gorelick's subordinate (and she concurred). More pithily:
[T]o sum up the exchange: The principal U.S. terrorism prosecutor was trying to tell her boss that she foresaw a real problem with the new and "not legally required" wall policy, but Ms. Reno--again delegating that policy to Ms. Gorelick--largely rebuffed her concerns.
The result? This:
U.S. Attorney for the Northern District of Illinois Patrick Fitzgerald summed up the core issue last October in testimony to Congress: "I was on a prosecution team in New York that began a criminal investigation of Osama bin Laden in early 1996. . . . We could talk to local police officers. We could talk to other U.S. government agencies. We could talk to foreign police officers. Even foreign intelligence personnel. . . . But there was one group of people we were not permitted to talk to. Who? The FBI agents across the street from us in lower Manhattan assigned to a parallel intelligence investigation of Osama bin Laden and al Qaeda. We could not learn what information they had gathered. That was 'the wall.' "
The 9-11 Commission is a joke.