I will take a crack at your question, by addressing what hutsitedigger, keppy, and storm-rider have said so far (as a way of answering your OP question):
For hut-site-digger, you say:
" .... public beaches and some public parks do allow it but you have too check with the park too see if they do ...."
You've got that bass-ackwards. Something need not be "expressly allowed" in order to be able to do it. For example: are you expressly allowed to fly frisbees? No. On the contrary. If there was/is no prohibition about flying frisbees at a specific location ... then ... one assumes he can fly frisbees. So a person does not need to seek to find out if there is an "allowance" of metal detecting. Instead, all they need to do is find out if there any prohibitions.
Next you say: " .... sometimes even if they do allow it they will tell you are not allowed too....." Huh? What sense does that make? If they "allow it" (the absence of a prohibition), then .......... by logical deduction, they can not say "you are not allowed". If they DID that, then you are a victim of "no one cared, TILL you asked". In which case you would have been better served to have looked it up for yourself, to have answered the question.
Lastly you say: "Just check the rules and regulations before you hit up a park." Right. And the best way to do that is to look them up for yourself. Not go asking desk-bound bureaucrats "can I?" type permission questions.
As for Keppy, I agree. What he's saying is that when you ask someone "can I?", you often get the "safe answer" of "no", even though no rule exists saying "no metal detecting". And if you press them by saying "... but where is that written?", guess what will happen? I mean, let's face it: our hobby has connotations (you might disturb something, etc...). And the mere fact that you are standing there asking them, merely assumes something is inherently wrong or evil, that you had to ask, to begin with! (lest why would you be asking, if it were innocuous?). So guess what they're safe and easy answer is going to be? Doh! They'll morph something to apply, even if .... the thought or concept never occured to them, nor would they have ever paid you a second glance! (unless you were being a nuisance in some other way).
As for storm-rider's reply, I bet that the very reason why he thinks his area is "tight" (and perhaps even is) is the very self-fulfilling pyschology that I speak of. The reason "The list of places closed to detecting just keeps getting longer." Is because too many md'rs keep making themselves a BIG RED X in need of attention, scrutiny, sanction, allowance, permission, etc...... And each time this comes before "some princely board for say-so", guess what the easy answer will be? So ironically .... if Keppy truly has an area that's free-flowing and you can detect public parks without having to ask, or having rules, well guess why? Because keppy and others in his area didn't go grovelling for "permission" (as if it were needed).
Next storm-rider says: " Sad to say, it's mostly the fault of folks who dig holes and leave them unfilled." Oh sure, this is the reason that some governing authority will tell you as their "go-to" reason for telling you "no". And perhaps there even WAS someone who "left holes" in the past. But let's face it fellows: what is the mental image when you talk to someone about metal detecting? HOLES! (I mean, afterall, we have to dig to get our targets). So even if there's never *really* been an issue or incident, this will be the knee-jerk reaction of the person you are asking. So when they say "no, because of holes", we md'rs say to ourselves "durn those people who must've left holes", when perhaps there was never even such a case! Or if there WAS such a case, it ONLY became a reason for a "no", when someone subsequently went in and asked "can I?". I mean, let's face it: HOLES (un-filled anyhow) are ALREADY a no-no for public land (under clauses like "defacement" , or "alterations", etc...), so .... what gives?
Lastly storm-rider says: "Many small towns don't have a specific ordinance against detecting but have a catch-all ordinance that prohibits "digging"." Ok. Granted, "small town have ordinances against digging". Let me save you some time: ALL places have ordinances against "digging", or "defacement" or "vandalism" or "alterations", etc.... But no, I do NOT automatically equate those to metal detecting. If you do, then sure, hang it up right now, or stick to private land with permission. But what you are failing to realize, is all such clauses instinctively and inherently apply to the END result, do they not? So if you leave no trace of your presence, then by logical definition, you have not alterED, defacED, or vandalizED anything ... now have you? Sure someone can debate you on semantics over the temporary evil process of extraction! For pete's sake, did you plan on wearing neon orange with a big red X on your back? Can't you go at low traffic hours and avoid such lookie-lous??
So to answer the OP's question: Look things up for yourself (if you are skittish). And if the entity (city, county, etc...) has nothing saying "no metal detecting", the presto, it's not prohibited. Just use some common sense. Avoid obvious historic sensitive monuments, go at low traffic times, be discreet d/t the mental implications, etc.....
