I used to deal in CW relics in the mid 80's. A friend of mine, another dealer, got offered a large collection of bullets dug at Gettysburg. He called me and asked if I was interested in going halves. I said yes and he bought them. It turned out the seller had been a student at Gettysburg College and in the summer worked for the park service. Some two months after buying them, my friend got a visit from the FBI. They wanted to know where he got the bullets from. He told them the story and luckily they let him off the hook. The student worked on the night shift and would do some midnight detecting. He labeled all the bullets with the location where he found them. My advice is to not go anywhere near the battlefield with a detector in the car.