Proven is always a strong word. But they're https://lawtechuk.io/explore/ukjt-digital-disputes-rules integrated into legal contracts using this rule set and that's well understood. There's no real problem with smart contracts under English law: there's clear evidence of intent to form an agreement, a payment is made etc. It's pretty uncontroversial.
In US there are all sorts of rules about various kinds of conveyances. Real property requires a recorded deed or the seller can just resell (and its legally binding against you), copyright requires a signed writing, etc.
