Does the BTC legally belong to the company, or the users, if it was given by mistake? Would they be within their rights to sue for it to be restored? I'm assum

Does the BTC legally belong to the company, or the users, if it was given by mistake? Would they be within their rights to sue for it to be restored? I'm assuming it works the same way as for errors involving fiat currency, but I'm not clear on what the law says in that situation either.