Where Should I Check To Find Local Laws About Detecting?

Thanks.
I am in Minnesota and the majority of my searching would be in Anoka county.
I havent been able to find much about it on the county website.

Hmm... Interesting advice. I might end up trying it if I cant find anything saying it is prohibited.
Follow up question.. If it turns out to be illegal and the cops show up, if I havent dug anythign up yet, can they do anything about it other than just tell me to leave? Just being in a park with a metal detector cant be illegal.. it must be actually digging and taking somehing.. right?

I have only had one problem so far in 5 yrs. Some lady came up to me and my cousin with her teen daughter and 5 small dogs and told us we couldn't md at the school, even though it was the weekend. I wasn't in the mood to argue with her, but when my father asked her as we were leaving 20 minutes later (yes, she ignorantly placed herself and her dogs in front of the gate) she said we needed a day use permit. I called the school district the next day and asked about a day use permit (although I didn't mention mding) and they told me it was not really enforced for sports because the school grounds were the only place in town for children to get outdoors. I will do some more research if I ever decide to go back to md the school, but will mention my intentions this time.

I am not 100 percent on the laws over there but I can offer advice as in my 28 years as a 'coin hound' I have probably tried everything!
First thing is if you are going to a 'public' place and are unsure of the law, have your excuse ready. "sorry but my wife lost her ring here".
Second, along riversides are a good place to detect (if not posted as private property) as it is very difficult to establish ownership.
Thirdly, do a little research and hit any local beaches you have that have been used by the public for years. These are not owned by anyone at all and you have complete rights to detect, dig up and more importantly keep everything you find. (in the UK you need a yearly permit and need to use a loophole to keep stuff that the 'crown' claims)
Fourth, find a metdet club!! They will put you straight!
Personally, if after pawing over old maps and diaries and history books (and google earth) I think I have a good spot to uncover what I am after, If I can't get permission I put my camo on and start detecting just as the light is fading.
Naughty boy, I know, but lets face it, us metdets provide a valuable service to anyone interested in the history of our ancestors.
Lastly, in the UK we have different areas that are under control by different 'councils' or boroughs. If you have the same there its a good idea to find the boundaries and detect pretty much along them. The authorities find it very difficult to challenge you as they dont know whos land your on.