Concerning the question of wizard vs. muggle protection by sacrfice:
In book 4, ch. 33 (the same bit of Voldemort's speech that KyKid942 quoted on p. 2), Voldemort says:
„But how to get at Harry Potter? For he has been better protected than I think even he knows, protected in ways devised by Dumbledore long ago, when it fell to him to arrange the boy’s future. Dumbledore invoked an ancient magic, to ensure the boy’s protection as long as he is in his relations’ care. Not even I can touch him there…“
Unless Voldemort is mistaken about the way love protection magic works (after all, it's not his area of expertise), this seems to imply that a sacrifice won't give you protection automatically. It seems to require a wizard (and presumably a rather powerful one) to "activate" the protection. If we assume that this kind of magic is not widely known -- it is "ancient", Voldemort thinks it has been "devised by Dumbledore", and even McGonagall doesn't seem fully aware of its significance, nor do the Weasleys, who try to persuade Dumbledore to send Harry over to stay with them right away -- it seems like this type of protection is not at all common. In my view, Harry may well be the only person under this protection at the moment.
However, this wouldn't necessarily exclude Muggle families from using that protection, provided that a wizard "activates" it for them.
How this fits with the protection Harry gives to his fellow warriors in the battle of Hogwarts, I have no idea. Maybe this is yet another kind of protective magic that we're presented with.
I believe that the protection mentioned wards Harry against Voldemort and his magic. (Apparently, this would extend to the Death Eaters, because they are agents of Voldemort. The Dementors, as agents of the Ministry (and of Dolores Umbridge in particular), are not bound by that protection.)
I think that Dumbledore did something to attach the protection to the house and surrounding area, and to extend/increase the protection, but, based on the fact that Harry's self-sacrifice protected everyone at Hogwarts without anyone knowingly doing anything to activate it, I would say that Voldemort couldn't have touched Harry or harmed him with his magic until after Harry's blood (and the protection contained within it) had been made part of his body in the Little Hangleton graveyard scene at the end of GoF.
I'm thinking as I type here (never a good idea), but I think this (the protection granted by Lily's sacrifice and, under my proposition, is automatically invoked and is able to be terminated by "becoming one" with the beneficiary of the sacrifice) doesn't explain why Privet Drive remained safe for Harry even after Voldemort had taken Harry's blood into him. I'm still working on that part. Keep chiming in, because it looks like I need the help.
Can you provide the source for that?ASU Sun Devil Quidditch
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