Is there a specific law? I've only heard that there are warning signs about possible live ordnance in the woods, but I think it's up to the persons themselves. If there aren't other people around who could get hurt of course. By border areas, I think you mean border zone's, where you need an permit by the Border Guard, to visit in. I know some people who have dug there. Also I've heard that only the memorial areas are only are protected. You're Finnish?