There are several generic problems connected with financial regulation. Among them, two perennial problems are associated with the existence of important, but porous, borders, or boundaries. The first such boundary is that between regulated and non-regulated (or less regulated) entities. The second, key, border is that between states, where the legal and regulatory systems differ from state to state. In this article, we explore these two boundaries. Oxford University Press 2010, all rights reserved, Oxford University Press.