We apply the paradigm of the firm as a nexus of contracts to the debate on regulatory competition vs. unification of law as an alternative way of regulating the business corporation. This approach views the business corporation as a set of coordinated contracts among different parties. Agency problems and related agency costs are the result of this interaction. The economic analysis of corporate law, securities regulation and bankruptcy law identifies law as a means to minimise such agency costs. In this paper, we develop a model where companies are heterogeneous in their preferences about the legal regulation of contractual relationships. We then compare a regime of regulatory competition with one of single supply of regulation and we analyse their relative costs and benefits.