If someone buys product x from seller y, which is based on some decentralized ‘contract’ which is defacto enforced by every node of the network independently - and that product then produces a unjust outcome.
You go to court, but what if Y is just a node on the network? And everyone involved is outside the courts jurisdiction? what can an adverse court judgement actually accomplish? It can’t roll back the network activity to fix the smart contract without everyone’s consent - and that seems unlikely. It can declare product X illegal or fine seller Y - but if they have no way to enforce it, what’s the point?
If the seller is unidentified, then it is possible to get a judgement and work on identifying them. If it's not just a civil dispute but felony fraud, then law enforcement might identify them some years later, it happens.
Of course, if everyone involved is properly anonymous then it's very, very hard to enforce anything, and takes enough effort and money so that it's not worth the hassle for small amounts, so for that there's simply some 'caveat emptor' in dealing with foreign anonymnous sellers. If you defraud $10 off of someone across the ocean, you are likely to get away with this. But for large cases of fraud? Everyone makes mistakes now and them that may allow them to get identified, and such fraud can be prosecuted many years later.
If Y can’t be hauled into court because they are in another country or you just don’t know their identity, well that isn’t a problem specific to these “distributed smart contracts.”
In this case, you send some ether somewhere.
Those things are not a small deal.
An agreement is an agreement subject to laws and jurisdiction. There's no avoiding that.
It will be interesting to see how this plays out in the courts.