Like the title says what are the rules. If I miraculously got a private key to a wallet that had Bitcoin in it but was not mine originally then does that mean I now own the wallet like finders keepers and is there any legality issues with this in the usa,uk,canada,south america. Is this more of a morality should you or should you not.
Where did you find the private key? If you find it in a place where you can easily trace the owner, it will be wrong to claim the coin. The ideal thing to do is to look for the owner and transfer the keys. It becomes more complicated if you don't know who owns the bitcoin and it is impossible to trace the owner. Let's say there was a natural disaster like a flood and you see a metal that has these keys in your garden. And there is no announcement of any missing keys from anybody. At this point, your reaction will be based on morality. You might decide to keep it or donate it to charity. You will have to explain to the government how you got such an amount. They might suspect that you got it through illegal means.