Legal Preemption and the Prevention of Chronic Conditions.

State and local legal innovations to address chronic conditions are an ongoing source of public health improvements. For decades, some of the most ingenious law and policy ideas to address the underlying causes of chronic conditions and their contributing factors have emerged from state or local public sector grassroots initiatives in diverse areas, including tobacco use, safe housing and transportation, and environmental hazards. These reforms, however, are susceptible to invalidation through the legal doctrine of preemption. Embedded throughout our constitutional system, preemption refers to how state or local laws may be averted, displaced, or negated by conflicting laws at a higher level of government. Preemption can be complex in concept and application, leading to considerable confusion among public health leaders seeking to generate meaningful policy proposals. The objective of this article is to unravel the legal concept of preemption, explain its use as a tool to both thwart or further public health interventions, and offer practical guidance for how to legally navigate around it to address factors underlying chronic conditions.