Yes. On the federal level, in all federal parks, all US Parks, and historical sites and monuments there is no hunting allowed. You could theoretically be arrested for just having a metal detector sitting in your car in a national park. Most rangers are not that ridiculous, but they could be about 60%, about two-thirds of the state has some type of restrictive park rules for the state parks. It varies from Minnesota, which absolutely says no use of a metal detector in any state park. In Wisconsin you have to get permission of the state park by meeting with the individual state park manager. In some parks, they will allow you too. You have to pay $5 and you get a permit. In other state parks, for instance the historical state park, they just say "no." It varies tremendously. About two-thirds of the states have some sort of regulation varying from "absolutely no" to "yes, you can do it at this time, under these conditions." Of course, the cardinal rule is to just ask. If you are going into a state park, ask if treasure hunting is allowed. Most cities in the US have no restrictions on treasure hunting other than restrictions on vandalism; don't destroy property. As far as I am concerned, the profitable treasure hunting is on private land, and you cannot hunt on any private land without asking permission. The greater percentage of property owners, if you ask them politely and tell them what you would like to find, they'll let you hunt, but not all.
