The ability to use magic: a skill or a talent? Is there a "mundane" population, then?
Why are Mastery and Gates the only two "forbidden" schools, given the infinite capability for harm, chaos and control other schools can grant one?
You can pacify rabid animals with Mastery, teleport wounded to hospitals with Gates, and drive people insane with Glamour.
How does magic law enforcement look like here, and how exactly does one trace the misuse of magic back to the wizard if all you have is a fiery crater or an islandquake?