Karl Polanyi started his career as adoctor of law and practiced law for awhile; but he did not become alegal scholar. As an economic historian, anthropologist, or sociologist, he was concerned with the relation of economy and society. But even though law is an important factor in mediating this relationship, Polanyi gave little attention to the law as such. As part of an endeavour to advance aPolanyian' economic sociology of law, this article develops the law of market society' as an analytical category. For this purpose, three argumentative strategies are combined. First, the article draws on The Great Transformation to reconstruct the role of law in the processes of commodification and decommodification. Second, it turns to Marxist scholarship to explore the conceptual link between law and economics and to ponder to what extent law itself can become acommodity. Third, it links Polanyi's approach with American institutionalism, and Commons' work in particular, to show how the evolution of the law of market society' can also be understood as acollective enterprise which continuously evolves. It is argued that these perspectives complement each other and help to bring the law back in where it is missing.