Law is one of the primary tools used in public health to promote healthier environments and behaviors. Governments at all levels use statutes, regulations and other policies, often in innovative ways, to make our communities healthier and safer. The effective and efficient use of law as a public health intervention depends upon research to evaluate what works and what does not, and diffusion of information to speed the adoption and implementation of laws that improve health. The term “Legal Epidemiology” is apt for this public health law work, capturing both its importance and its scientific nature. Legal epidemiology may be defined as “the scientific study of law as a factor in the cause, distribution and prevention of disease in a population.” Within legal epidemiology, “policy surveillance,” the systematic tracking of policies of public importance, is an emerging practice that supports both scientific evaluation and the diffusion of policies the work for health. The Robert Wood Johnson Foundation’s Public Health Law Research program (PHLR), working in collaboration with the Centers for Disease Control and Prevention’s Office …