To analyse the tobacco industry's use of international trade agreements to oppose policies to strengthen health warning labels (HWLs).A review of tobacco industry documents, tobacco control legislation and international treaties.During the early 1990s, the tobacco industry became increasingly alarmed about the advancement of HWLs on cigarettes packages. In response, it requested legal opinions from British American Tobacco's law firms in Australia and England, Britain's Department of Trade and Industry and the World Intellectual Property Organisation on the legality of restricting and prohibiting the use of their trademarks, as embodied in cigarette packages. The consistent legal advice, privately submitted to the companies, was that international treaties do not shield trademark owners from government limitations (including prohibition) on the use of their trademarks. Despite receiving this legal advice, the companies publicly argued that requiring large HWLs compromised their trademark rights under international treaties. The companies successfully used these arguments as part of their successful effort to deter Canadian and Australian governments from enacting laws requiring the plan packaging of cigarettes, which helped delay large graphic HWLs, including 'plain' packaging, for over a decade.Governments should not be intimidated by tobacco company threats and unsubstantiated claims, and carefully craft HWL laws to withstand the inevitable tobacco industry lawsuits with the knowledge that the companies' own lawyers as well as authoritative bodies have told the companies that the rights they claim do not exist.