Drug addiction is a major public health problem, one that is most acutely felt in major cities around the globe. Harm reduction and safe injection sites are an attempt to address this problem and are at the cutting edge of public health policy and practice. One of the most studied safe injection sites is INSITE located in Vancouver, British Columbia. Using INSITE as a case study, this paper argues that knowledge translation offers a limited framework for understanding the development of public health policy. This paper also argues that the experience of INSITE suggests that science and social justice, the meta-ideas that lie at the core of the public health enterprise, are an inadequate basis for a theory of public health policy making. However, on a more positive note, INSITE also shows the value of concepts drawn from the ways in which political science analyzes the policy process.