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.
There are no preestablished rules for that and you will need to decide what to do on your own, however the chances of that happening are very low, address collision is almost impossible so finding a private key or a series of seed words will need to happen by just finding a piece of paper or an electronic device with that information, which means there could be some ways to determine the origin of those coins, besides if the owner of those coins is smart they should realize they have lost heir coins and move them out of that wallet as soon as they can, not giving too much opportunity for this to happen.