This chapter discusses how forms of 'co-operative law' elaborated by public authorities within co-operative regulatory bodies provide governance to the international and European financial markets. It gives an overview of the current arrangements allowing co-operative law-making to take place and of the sort of rules being produced. The chapter aims to grasp the nature of this co-operative law, its regulatory features, its circular effect on co-operative regulatory bodies, and whether it may be perceived as having a legal character. It assesses the procedural and non-procedural features of a transnational order whose shortcomings are far less than apparent. In order to structure the evolving corpus of transnational co-operative law, the participants in regulatory groupings have defined certain fundamental assumptions as the basis to proceed with co-operation itself. The chapter provides an overview of the international co-operative for dealing with the regulation and supervision of financial markets, primarily in the sectors of banking and securities markets.