Public nuisance has recently been dusted off as a potential source of legal redress for tobacco use, handgun distribution, lead paint removal, MTBE contamination, and global warming. The premise of this litigation is that public nuisance is a tort, and that courts have inherent authority as common law tribunals to determine what conditions qualify as a public nuisance. This article argues that public nuisance is properly regarded as a public action rather than a tort, as revealed by a number of its features, including the nature of the interest protectedrights common to the general publicand the traditional understanding that public nuisance is a crime. The view that public nuisance is a species of tort liability is a product of the Restatement (Second) of Torts, which sought in the 1970s (without notable success) to transform public nuisance into a weapon to combat environmental harms. If public nuisance is properly regarded as a public action rather than a tort, then the effort to enlist public nuisance as an instrument of social reform without authorizing legislation suffers from a delegation deficit. Public nuisance, like other public actions, should not proceed unless the legislature has first specified the circumstances in which liability exists, and who has authority to bring an enforcement action. This means courts should disclaim any inherent authority based on the common law to declare that particular conditions are a public nuisance. It also means that existing public nuisance statutes, which were typically adopted years ago with a different order of social problem in mind, should be interpreted non-dynamically, in order to preserve the principle that public actions must be grounded in enacted law rather than a claim of inherent judicial authority.