Brandon, you want to know the sad fact of all your efforts to clarify things? I'll bet that the very clause you started with "
....... with the permission of county administrator" (that caused you to ask multiple clarification/permission questions) only GOT THERE TO BEGIN WITH, because someone before you (whatever # of years ago) went to park personell seeking to know "can I metal detect?". And then guess what happens? If there were no rule at the time (which there usually wasn't in the old days), they simply "address this pressing issue" by MAKING RULES! Doh! I mean, the mere fact that someone is standing their asking permission, simply means that something is inherently wrong, or damaging, or evil about it, that they had to ask, in the first place! (eg.: would you have "asked" to fly a frisbee?) So with this inference in mind, quite often the answers people would receive is "no", or "inquire at each park you come to" or "only with permission" etc... And how did that all start? Someone asked! And truth be told, probably no one would ever have given the matter thought, or even have noticed them, if they'd just gone.
Proof in Point: Notice, as you yourself say: "
.... but this time, he sent it not only to me, but a TON of other park people" Now do you see what's going to happen? Whereas the rank-&-file perhaps would never have bothered you, because perhaps they don't care, and don't know some dusty minutia like this, are now made aware of some "rule", and then guess what's gonna happen, the next time those other park personell see an md'r? They're gonna have this "B.O.L." memo fresh in their mind, and start thinking "aha! there's one of them", and start booting others (to whom they'd have probably never paid mind to before". So your efforts, in effect, essentially get laws/rules WRITTEN (or enforced, or cared about, or morphed to more serious levels, etc....).
I know you find yourself in a catch-22. While what I am saying is the psychological effect of asking desk-bound bureaucrats "can I?" But on the other hand, you can point to something that says you have to ask. Thus you find yourself in a vicious circle. But you've got to ask yourself "how does this cr*p get started?" By persons in the past asking "can I?" when no real rule or prohibition exists (barring being some sort of nuisance, leaving a mess, or whatever).
Your area may be "too late", as all the people before you, and you yourself, have simply made this hobby a big target now. But this should/can hopefully be a lesson for others to not let this crazy vicious circle get going, to begin with.
A thread I made on this topic, which shows a "could be" case of this:
http://forum.treasurenet.com/index.php/topic,249049.0.html