If cops argued before that they needed to keep the public 20' away from incident A-- "totally not" to prevent filming, but for public safety-- that argument doesn't vanish or really weaken now.
I understand what you're saying, but this doesn't establish some kind of right to be within 8' of an officer and probably doesn't change the evaluation of most situations substantially.
Officers have a whole lot of reasons to want to keep the public farther back- Tueller drills, if I were scuffling with some dude I'd not want a potentially-hostile observer 10' away, standard training about perimeters in static situations, etc. Those don't evaporate, and they generally can be argued for even if the real motivation is preventing filming.
> But for an even less theoretical example, state laws have explicitly legalized marijuana, for instance.
Yah, I'm not interested in arguing the philosophical question of whether all laws are in some sense prescriptive-- nor of whether removing past restrictions counts as adding a law. I just don't think the AZ public is better off or more able to film with this new law.