Ah, but he understands so little about our legal tradition. The law of contracts is enshrined in the common law and it is preserved in our constitution, Article II, Section 10: "No State shall ... pass any .... Law impairing the Obligation of Contracts."
De Soto has the right idea that OTC derivatives should be traded publicly for all to see. OTC trading of derivitives is antithetical to our tradition of being able to trace financial paper to an asset