It does not have to be before the work begins, but it should be. That will avoid possible conflict. Unequivocal is maybe too strong of a word. In the US, we choose the shitty common law system, so any judge can start legislating. This means there could be cases that undermine what Title 17 articulates. I will try to look at Community for Creative Non-Violence v. Reed tomorrow and see if I can paste a full copy of it here. Most USSC cases are longwinded though. Btw, the circ09 document is not binding on anything. At first glance, I assume it is a law review article written by a federal bureaucrat. You really have to look directly at the case it is opining over.