Campaigns to limit tobacco use started in the 1970s and have led to bans on public smoking, which have been extended to parks and beaches. A review of state and local statutes shows that during 1993–2011, smoking was banned in 843 parks and on 150 beaches across the United States. Three justifications for these restrictions have been invoked: the risk of passive smoke to nonsmokers, the pollution caused by cigarette butts, and the long-term risks to children from seeing smoking in public. Our analysis of the evidence for these claims found it far from definitive and in some cases weak. What, then, accounts for the efforts to impose such bans? We conclude that the impetus is the imperative to denormalize smoking as part of a broader public health campaign to reduce tobacco-related illness and death. Although invoking limited evidence may prove effective in the short run, it is hazardous for public health policy makers, for whom public trust is essential.