Hmm, I see. I was forgetting domestic terrorism by foreign elements. So is the FBI forbidden to do surveillance on, for instance, suspcious mohammedens? Probably I am too much a simpleton to delve any more into this topic, as interesting as it is.
No, but without access to intercepts, they will have to rely on non-LE analysis for determining 'suspicious mohammdens', making their cases less in-depth. The senior leadership sucked, but there should be an in-house cadre that goes through an NSA vetting program for this type of CT as well as rooting out suspected spies foreign and domestic.