Do you see the common theme in a lot of the comments here? People "asked", and were told "no". Or maybe it wasn't exactly THEM that asked, but the person booting them references an earlier inquirer, to whom they had told "no". Do you get it? With certain exceptions, I think sometimes WE are own worst enemy. All we do by going around asking, is to caste aspursions on ourselves, as if metal detecting were somehow inherently evil enough, that we had to "ask", to begin with! The minute you do that, you will easily find some deskbound bureaucrat, whose image is geeks with shovels leaving a mess, to say "no". And truth be told, you'd probably have been ignored, if you'd just gone. Ie.: a lot of times, they don't give it thought, UNTIL you ask. Yes, of course, if you're not being discreet about your digging/holes, then yeah, someone will say something. That is because, no matter how well you replace, stomp, etc..., the only image in a passerby's mind, is when they saw you half way through a recovery. No matter how much you tell them "you won't even be able to tell I was here", their only image is the recovery half way through.
There is NO park in the entire United Sates ANYWHERE, where ...... if you walk into the park's dept. and ask "can I dig in the park?" that will tell you "yes". I mean, C'mon! So c'mon guys, just go at off-times where you don't stick out. Go at low traffic times, and don't start a recovery (unless it's shallow clad) if some busybody lookie-lou is watching. Yeah, I know this doesn't apply at parks/cities that ALREADY have rules, but for cities who don't have anything concrete, why would you want to raise a bunch of attention to yourself or your hobby?
In my city, our parks and schools were, and still are, routinely detected, at will, and no one has ever cared. When I first started detecting in the 1970s, we naturally went to schools and parks. It never even occured to us we might need to "ask". I mean, afterall, it's a public park, right? We'd go right in front of anyone and everyone, including gardeners, and never had anything but a friendly wave. But then one day, a newbie to town shows up at one of our club meetings. He hears a fellow say that such & such old coin was "found in central park". He objected and says "I thought central park was off-limits?" We say "since when? Who told you this?" etc... Turns out, he'd gone to city hall and asked! This kind of scared a few of us, because now we were concerned that maybe there was a new rule or something. Or, maybe it was a fluke answer by some desk-bound person, but, guess what might happen when that same person passes the park, see a different md'r, and remembers the earlier inquiry? Whereas they might never have noticed or paid attention to a detector before, NOW though, they might remember the earlier inquiry (like 'aha! there's one of them") and start booting people!
It's a catch 22 situation. Because admittedly, although only a small percentage of cities ever have any rules (or enforcement) to do with detecting. But the mere fact that a few cases get put on web forums, cause other people to rush out and "see if there's any rules in their town", and the attention just snowballs, as city folks go to "address this pressing question".
Another example: In San Francisco, there are probably over 100 parks of various sizes and shapes. There is, as far as we know, nothing specifically written that addresses detecting. Perhaps "disturbing the vegetation", but nothing about detecting. Now and then, once in a blue moon, someone will get the ire of a gardener or passing bureaucrat. So we just "move on", and make it a point to avoid just that one park, or just that one person. From what I gather on the forums, others would take big issue with that, and assume "Oh now! All the parks in my town are off-limits" and proceed to take it to the highest levels, ending up often-time, doing more harm, than good. Ie.: taking isolated situations, and ending up getting actual rules or enforcment.
So unforutantely, our hobby is like nose-picking. If you enough people "can I pick my nose?" Someone will eventually tell you "no". Or if you stood on the street corner long enough picking your nose, someone would eventually take offense, and boot you (as a traffic nuisance or something). But on the other hand, if you discreetly pick your nose, and don't stick out like a sore thumb, you are usually ignored. Gross analogy, but kind true in a wierd way.