Your comment is a non sequitur. Blockchains already depend on physical matter, human social behavior, game theory, and yes, the legal system. Mining farms require legal protection to prevent marauders from commandeering them.

An example of a blockchain/legal system hybrid is colored coins, where a token represents a real world asset. The legal system is required to enforce whatever contractual obligations are implied by that token. But it still adds value over a purely legal approach as at least ownership and transfer of it is transparent.