If you use Bitcoin, then you are the legal owner of Bitcoin. That is why Bitcoin is being regarded as a decentralized currency. No third party is involved when you use BTC. It is your responsibility to hold or transact your coins. A dispute over ownership can arise in some cases. For example, if someone steals your coins after hacking in to your wallet, then you need to file a police complaint and claim that your digital assets were stolen by that person. Satoshi is not going to help you in that case.