Publisher Summary This chapter discusses the role of regulation in the markets, and more specifically about the role of government regulation versus pure selfregulation by the market. Economic models of markets are just that models which are simplified and stripped of imperfections to fundamental principles. From a regulatory point of view, standardization is necessary in such areas as pre- and post-trade data flows to permit consolidation and dissemination to the marketplace. The most important element of state regulation is that it brings with it the authority to require an action to be taken. The strength of state regulation is its overarching authority and the strength of market selfregulation is its detailed knowledge of the market. However, the state regulation is critical to the achievement of market integration, even if its role is limited. The achievement of true market integration should be a matter for the markets with cooperation, authority, and direction of appropriate state regulation.