The premise is that most mortals refuse to accept that magic, and the supernatural, exists. So, 'keeping the secret' is more a matter of keeping information from reaching those mortals who would accept magic, and have enough real power to do something about it.
The Chicago Police Department has a squad assigned to 'disturbing' cases with the unwritten rule being to make these cases go away and not reach the papers...somehow. Explain things, make things normal, don't bring up ideas that no one will believe and that would embarass the Department. So, most mortal authorities work with the supernatural community to keep things hidden. Most.
Fool Moon is an example of what can happen when you combine mortal authority with supernatural power. Which is why everyone works to try and see that this doesn't happen.
And if a PC becomes a Warden, then I woulnd't suddenly impose a bunch of restrictions. This is a game about being able to do what you want...if you're willing to accept the consequences.