Spit and shake hands as much as you want, brother, but only signature with your private key counts in the end!
Nope. Go ask a lawyer. No matter which party ends up with the asset at the center of a smart contract dispute, that said ownership can still be challenged in a court of law. Smart contracts will not alleviate or nullify this.
Riddle me this: Since you and me never signed which jurisdiction is recognized in case of the dispute, and we may be from different countries, do you really believe jurisdiction of my country has power over you?
Riddle me this: Why or when would I ever go into a smart contract with you, knowing this? Lol
Because we want to be a free men, not begging for the protection of the higher authorities, and leave our disputes for math to resolve it. I agree that smart contracts in it's present form are not particularly useful, but I'm convinced we will sooner or later see emergence of entities who's ownership of the stocks will be resolved on the blockchain, instead on government controlled stock markets. Your signature is your vote, etc.