I'm thinking about the legalities of these guys running around with metal detectors on what would presumably be private property. I know it's not legal in parks etc, here without a permit or permission from the land owner.
Metal detecting in Germanyicon, for example, requires a licence. Apparently, there are a lot of places there(in the old East Germany mostly) that one cannot dig at all due unexploded ordnance all over the place. No keeping any weapons found either. Even rusty stuff. German Metal Detecting Laws
Net search this too.
List of countries where metal detecting is allowed/banned | MD-Hunter Blog