I was just curious, but for those of you writing fantasy involving forms of magic, what kinds of regulatory systems do you employ, if any at all? For example, if magic (for lack of a better catch-all term) is something everyone knows about in your story, are there people to make sure that not every average Tom, Dick, and Harry can learn it, or is it not necessary?

On an aside, I know it differs from setting to setting, but what are there any sorts of magic regulating devices or organizations you've liked from anything you read, or a typical schema that appeals to you?