Preemption is a powerful strategy used by special interest groups to undermine strong, local public health standards. Currently, 20 states in the U.S. have preemption ordinances in place related to clean indoor air initiatives. These preemption laws are the direct result of an ongoing and aggressive campaign of tobacco companies to thwart clean indoor air initiatives, which ultimately, according to tobacco industry internal documents, cause significant reductions in their annual revenues. Clean indoor air policies have arisen from a greater understanding of the documented health risks associated with exposure to secondhand smoke and action by local government (city councils, county commissions, and boards of health) to protect the public from these hazards. The efforts of the tobacco industry undermine local authority and seek to shift policy action to the state and federal levels, where the industry has greater political influence.