This paper uses insights from cultural theories of regulation and critical legal studies to argue that regulatory outcomes are not adequately explained by the activities of dominant interest groups. A more dynamic conception of the relationship between interests and ideas, especially legal ones, is required. Discursive shifts among languages of entrepreneurship, ownership, fairness, and market credibility are shown to be consequential for the outcome of the reform debate examined, not least because of the importance of these ideas, variously interpreted, in shaping the positions of interest groups.