The Wall had nothing to do with DOD or military intelligence doing surveillance of citizens. The later comes under the Posse Comitatus Law. That's what the DOD lawyers were concerned about - erroneously.
The "Wall" was within the DOJ, period. The intelligence side of DOJ was not allowed to talk to the criminal justice side of DOJ. When the "Wall" memo was written, Gorelick had absolutely no control over what DOD did or did not do.
DoD operated until the policies of lawyers put in place by Gorelich when she was its chief lawyer.
That is only partially correct. Posse Comitatus forbids the use of the military in law enforcement. The FISA Act of 1978, EO12333 from 1982 (and a bunch of others) effectively stopped all military investigations regarding US Persons (see previous post on that). The DOD Lawyers based thier decision on the fact that Atta & Co were, at the time, legally present in the US and that this came too close to being illegal.
The "Wall" was within the DOJ, period. The intelligence side of DOJ was not allowed to talk to the criminal justice side of DOJ. When the "Wall" memo was written, Gorelick had absolutely no control over what DOD did or did not do.
"Gorelick's Wall" extended to EVERY other department as well (NSA, DIA & DOD) because - the DOJ is the ultimate arbitrator of what is allowed and what is not! For example - in order for the NSA to investigate a US Person, they must first obtain permission from the AG.