We examine the process by which antitobacco laws and ordinances were implemented and enforced in seven states and nineteen localities. Our findings indicate that state- and local-level clean indoor air laws were rarely enforced by governmental agencies. Instead, these laws were largely self-enforcing in that changed social norms regarding appropriate smoking behavior led to generally high compliance rates. In contrast, teen access laws were not self-enforcing, but were often enforced through periodic vendor compliance checks. We also found that antitobacco forces did not devote a significant amount of attention of implementation and enforcement issues. Their focus was primarily on enacting new legislation and fighting tobacco industry attempts to weaken existing laws. Our results do not augur well for public health measures that require state-level enforcement and that are opposed by powerful and politically well-connected interests. For tobacco control laws to be effective, public health advocates need to consider the locus of enforcement responsibility and the sanctions available to the enforcement agency, such as license removal by local authorities. These results suggest that failure to specify such mechanisms in the legislation will lead to delays in implementing and enforcing the laws as well as to a number of compliance problems. Antitobacco coalitions will also need to become more actively involved in the implementation and enforcement process.