Some beaches are considered a "National Seashore" and the state parks have restrictions too. At Ft. Fisher, I used to go metal detecting there all the time and left it better than I found it, however the state or the people who run things believe we are "stealing" national treasures. Like musket balls and the sort are a valuable treasure, cool stuff, but not worth putting someone in jail. I do know that the fort is almost gone due to erosion and they want to keep it around so I understand. Cape Hatteras I have no idea. There is so much there to get and again I believe the government feels that people would be "stealing" national treasures.
I would love to find this stuff, just for kicks and turn it in, well most of it. Spanish silver & gold among other things of interest are there. I had my detector taken from me and threatened with a fine and given a citation at Hammocks State Park, they said it was not allowed. I did my homework before I went and printed the rules from their website that stated the contrary. They gave me back my detector and tore up my citation. I detected again and found nothing. Oh well, would have been great to find something of value right in front of them but....
I do know if you are detecting in say Ft. Fisher Park and find Civil War items you are to turn those in. To keep in their good graces I took some a cannon ball and some musket balls that I had found years before and turned them in to them. They don't hassle me anymore and have give me calls when people have lost a ring etc. Keeping in their good graces has made my life easier and I have returned several rings and jewelry items to their owners and made some money too.
Eric