Here are the seven hedges in Tolkien and Lewis.
Tolkien and Lewis confine the pursuit of magic as a safe and lawful occupation to wholly imaginary realms, with place-names like Middle-earth and Narnia — worlds that cannot be located either in time or in space with reference to our own world, and which stand outside Judeo-Christian salvation history and divine revelation. By contrast, Harry Potter lives in a fictionalized version of our own world that is recognizable in time and space, in a country called England (which is at least nominally a Christian nation), in a timeframe of our own era.
Reinforcing the above point, in Tolkien’s and Lewis’s fictional worlds where magic is practiced, the existence of magic is an openly known reality of which the inhabitants of those worlds are as aware as we are of rocket science — even if most of them might have as little chance of actually encountering magic as most of us would of riding in the space shuttle. By contrast, Harry Potter lives in a world in which magic is a secret, hidden reality acknowledged openly only among a magical elite, a world in which (as in our world) most people apparently believe there is no such thing as magic.
Tolkien and Lewis confine the pursuit of magic as a safe and lawful occupation to characters who are numbered among the supporting cast, not the protagonists with whom the reader is primarily to identify. By contrast, Harry Potter, a student of wizardry, is the title character and hero of his novels.
Reinforcing the above point, Tolkien and Lewis include cautionary threads in which exposure to magical forces proves to be a corrupting influence on their protagonists: Frodo is almost consumed by the great Ring; Lucy and Digory succumb to temptation and use magic in ways they shouldn’t. By contrast, the practice of magic is Harry Potter’s salvation from his horrible relatives and from virtually every adversity he must overcome.
Tolkien and Lewis confine the pursuit of magic as a safe and lawful occupation to characters who are not in fact human beings (for although Gandalf and Coriakin are human in appearance, we are in fact told that they are, respectively, a semi-incarnate angelic being and an earthbound star.) In Harry Potter’s world, by contrast, while some human beings (called “Muggles”) lack the capacity for magic, others (including Harry’s true parents and of course Harry himself) do not.
Reinforcing the above point, Tolkien and Lewis emphasize the pursuit of magic as the safe and lawful occupation of characters who, in appearance, stature, behavior, and role, embody a certain wizard archetype — white-haired old men with beards and robes and staffs, mysterious, remote, unapproachable, who serve to guide and mentor the heroes. Harry Potter, by contrast, is a wizard-in-training who is in many crucial respects the peer of many of his avid young readers, a boy with the same problems and interests that they have.
Finally, Tolkien and Lewis devote no narrative space to the process by which their magical specialists acquire their magical prowess. Although study may be assumed as part of the back story, the wizard appears as a finished product with powers in place, and the reader is not in the least encouraged to think about or dwell on the process of acquiring prowess in magic. In the Harry Potter books, by contrast, Harry’s acquisition of mastery over magical forces at the Hogwarts School of Wizardry and Witchcraft is a central organizing principle in the story-arc of the series as a whole.