The laws vary, but generally there are two parts to it...one, anyone can photograph anyone else as long as its not in a place where they expect privacy....change room, their home etc... two, publishing...this is what you need permission for unless its a news worthy event. And there are other laws that apply, slander, etc.. So, the short answer is, you should not publish anything that might do harm to anyone and if sending around an image of a CDer walking around walmart causes harm to that person they could sue you or press criminal charges.
The way I look at it, if I go out in public, nobody knows for sure who I am unless I tell them so my privacy is mostly protected. When you go out in public you also have to be prepared that someone might recognize you, but the chances of that are pretty low especially if you have put a lot of effort in to the transformation.
