A word of caution about organized hobbies and permits or insurance to experience them...I also fly electric RC planes as a hobby. I scratch build my own foam designs via hot wiring from construction foam to both save money and also for the experience of building whatever design I can think up in my head to see if it will fly and how it handles. I almost get as much enjoyment from building them than I do flying them.
But anyways, there was a loose organized "group" of us that would all get together at a massive sized park early on Sunday mornings to fly. It's a huge wide open area and we stay and flew in a back corner of it so as to not put others at risk and stay out of their way.
One day a lady decided to start complaining that we were flying over her house. I knew she wasn't telling us the truth, since her house was off through some woods and we never flew over those woods at the edge of the corner of the open field for fear of losing a plane in a tree or something. We didn't need to anyway, as we had plenty of open air where we were at. One day she even came through the woods and started complaining to me that I was flying over her house. I was sitting on a rock flying my plane, with my back to the woods, and turned around and said "That would be a neat trick, since I don't have eyes in the back of my head."
Sure, 99% of the time I'd never get smart like that, but I was sick of this lady harassing our flying group every Sunday for no reason. She was just one of those people who can't stand to see anybody have any fun. Our electric planes aren't very loud, and besides there was a nice buffer of woods between the field we flew in and her house. She just was "one of those types", if you know what I mean.
So anyway, a few of the guys in our unofficial group, decided that it would be a bright idea to approach the city and see if we could get written permission to fly there. I told them not to risk it, because the police come and watch us all the time anyway, so what's the point? At least one or two of these guys had made remarks before about us all joining the AMA, because they were members and then we could fly at their flying field (which required both AMA insurance and group dues, by the way).
Well, long story short, some few approached the city, and next thing you know it's AMA insurance required to fly there unless you've got home owners insurance that will cover it. There are many places to fly around the country these days where you are required to belong to the AMA to fly. The AMA was formed long ago, during the gas/nitro/big heavy balsa days. Many these days in this hobby are electric flyer's, with smaller lighter planes that can be flown in much smaller areas. Way I look at it nobody owns the sky and I resent being asked to pay to enjoy flying my planes in it.
So what happened? Our little informal group often would have 30+ people or say on any given early Sunday morning. Not all flying at once of course, we kept it down to 4 or 5 planes at the most at any one time in the air, and would land if any stray person even came close to that corner we hid in.
These days? Last I heard the little group had shrunk down to hand full of people, or in fact none might even fly there any more. We've all been scattered to our own personal places to fly, where as before we all had one central location to meet up at. I have large open fields to fly at on private property on a few farms, and I simply refuse to let certain guys from that former unofficial group tag along. I don't want people screwing up what we had before. I don't want to hear lectures about how it's the right thing to do to join the AMA. IE: To me, many organizations, wrongly or rightly in my mind's view, are more about protocol and paying others tribute for some position they hold in title, and of course never forget the money factor involved. I only invite a few select former flyers from the other field with me here and there. The ones I think I can trust not to go all AMA crazy.
I look at metal detecting the same way. The more we organize, the more those in power of that organization will take advantage of it, by way of dues or some formal respects we are expected to acknowledge as somehow "above the rest of us". I am far more into the idea of just pushing good digging techniques onto newbies to show them the ropes, than I am saying "sign this and pay this" and somehow expecting that to make it a perfect world by some magic spell of doing that.
Beware of those who seek power and prestige, because it's often more about them than it is about what they *say* they are going to do for you. That's the way I look at government too. The less of it the better...
PS- If we really wanted to do anything formal, I say the best idea would for the metal detector dealers to all be required to show each new owner of a machine bought from them proper digging techniques and manners in dealing with staying away from the public. Make it so the buyer will have to check off a box on their warranty card that the dealer showed them how to dig, recover, and repair a hole. Only would take 5 minutes in the yard of the shop, or say if they buy online then they are sent a video with any new machine that shows these things.
If they don't check off that box on the warranty card to send in, then if the manufacturer gets enough of those from customers who bought machines at a particular shop, the dealer gets a call and is asked "Why aren't you showing these people proper recovery techniques, or are you sending out the video with the machines that teaches it?" Put it in their contract that if they get enough complaints. Confirmed complaints that is, by way of calling the customer to see if they just forgot to check off that box on the warranty card, then the dealer loses his contract to sell those machines.
In the long run it's in the best interest of both the dealers and the manufacturers, as well as for us in this hobby. That's even a little more "big brother" than I like, but since it's not being imposed by some official body, I guess I can live with it...
By far the best way to avoid a problem is to avoid it in the first place. I try to fly under the radar. Never hunting near people in parks. Always keeping my back turned to the closest one or any road when bending down to dig so they don't "see the act of it". No shovels or military style short ones. Keep your digger in a holster until needed and use a screwdriver whenever possible. If a park gets too crowded to where I can't stay a good distance away from others then I leave to fight another day. If you do get approached don't argue. That only leads to the authorities being called and they always want to stop the complainer, so that means out you go. I have never lost access to sites I hunt over the years doing this.
Don't give people a reason to complain, and if they do just say "sorry I upset you" and come back another day. Chances are you'll never see them again in your life. Throwing around our rights, wrongly or rightly, is only going to get us banned, as we are far too in numbers to sway politicians our way. Also, never ask for permission to hunt public land unless there is a sign that says you have to, or that you need a permit. Only when a place is posted as off limits to detecting should any form of government be approached to see if you can change things. By asking permission to hunt on public grounds were none being required has been posted, you are only asking for a "no", in which case you can no longer use ignorance as an excuse.
We can't hope to change laws. We don't have the numbers or the money to fight many greenies out there for one thing. Just be like the sly animals in nature- Avoid being "seen" at as much as possible...
I think it would help. I have come upon more than one site where some idiot before me dug holes and did not cover them back up. They are just lazy bums in my opinion. If a permit was required then at least they might cover the holes if they think someone is looking. People who don't cover holes are like trash litter bugs. They just don't care. 
