“The problem of social cost” (Coase 1960) asserts a normative role for the judge, that of allocating the property right to the person who would pay the most for it. A possible inconsistency is often raised: Coase sees the figure of the judge as willing and able to reach economic efficiency, but criticises the actors of public intervention, particularly regulators, who are fallible, vulnerable to political pressures and lack information. The present article examines both this inconsistency and some elements of Coase's theoretical system that could justify it. I shall show that Coase's giving this role to the judge comes precisely from his criticism of public intervention. But this means that his judge escapes these criticisms and his comprehension of human nature on which they are also based. Consequently, the figure of the judge escapes the tenets of the theoretical system that first rendered it necessary. Some reasons could explain this difference of treatment between the judge and the other figures of public intervention in Coase's system, but Coase too strongly opposes common law on one side and regulatory and statutory law on the other, and he leaves unexplained the motivation of judges. Unearthing the implicit beliefs that underpin his argument in favour of common-law solutions to externalities contributes to illustrate its weakness and brings to light that this preference is presupposed rather than established.