Aims To describe the development and enactment of the Western Australian (WA) Cannabis Infringement Notice scheme and reflect on the lessons for researchers and policy makers interested in the translation of policy research to policy practice. Methods An insiders’ description of the background research, knowledge transfer strategies and political and legislative processes leading to the enactment and implementation of the WA Cannabis Control Act 2003. Lenton and Allsop were centrally involved in the process as policy-researcher and policy-bureaucrat. Results In March 2004, Western Australia became the fourth Australian jurisdiction to adopt a prohibition with civil penalties scheme for possession and cultivation of small amounts of cannabis. We reflect on: the role of research evidence in the policy process; windows for policy change; disseminating findings when apparently no-one is listening; the risks and benefits of the researcher as advocate; the use of the media; the differences between working on the inside and outside of government; and the importance of relationships, trust and track record. Conclusions There was a window of opportunity and change was influenced by research that was communicated by a reliable and trusted source. Those who want to conduct research that informs policy need to better understand the policy process, look for and help create emerging windows that occur in the problem and political spheres and, make partnerships with key stakeholders in the policy arena. The flipside of the process is that, when governments change, policy born in windows of opportunity can be a casualty.