Incomplete Law – A Conceptual and Analytical Framework and its Application to the Evolution of Financial Market Regulation

Katharina Pistor, Columbia Law School
Chenggang Xu, University of Hong Kong


This paper develops a conceptual framework for the analysis of legal institutions. It argues that law is inherently incomplete and that the incompleteness of law has a profound impact on the design of lawmaking and law enforcement institutions. When law is incomplete, residual lawmaking powers must be allocated; and enforcement agents have to be vested with law enforcement powers. The optimal allocation of lawmaking and law enforcement powers under incomplete law is analyzed with a focus on the legislature, regulators and courts as possible lawmakers, and courts as well as regulators as possible law enforcers. The timing and process of lawmaking and law enforcement differs across these agents. Legislatures are ex ante, courts are ex post lawmakers, regulators have combine ex ante and ex post lawmaking functions. Courts are reactive law enforcers, while regulators are proactive law enforcers in that – unlike courts – they can initiate enforcement procedures. We argue that the optimal allocation of residual lawmaking and law enforcement powers is determined by the degree and nature of incompleteness of law, the ability to standardize actions that may result in harm, and the magnitude of harm and externalities expected from such actions. Under highly incomplete law, regulators are superior to courts when actions can be standardized and, if allowed to proceed, may create substantial externalities. Otherwise courts are optimal holders of lawmaking and law enforcement powers. We apply this analytical framework to the development of financial market regulation in England since the mid-19th century, with comparative reference to developments in the United States and Germany. The comparative evidence suggests that financial market regulators with both residual lawmaking and proactive law enforcement powers emerged in all three jurisdictions in response to ineffective judicial law enforcement of highly incomplete law.