Explaining drug policy is not an easy task. As Alison Ritter (2022, p 79) puts it, drug policy ‘often seems to occur without much logic’. Explanation requires the discovery of some underlying logic, even if it is not particularly rational. As this logic is underlying, it cannot be directly observed. But we can use a variety of research methods to improve our understanding of how it works, of the mechanisms that combine, in some situations, to produce particular drug policies.

There are some excellent books that point the way towards such explanations. I have learnt a lot from Ritter's short but magisterial monograph on Drug Policy. Another is Susanne MacGregor's (2017) book on The Politics of Drugs. People who are interested in the history of British drug policy will gain a lot from it, as they will from Virginia Berridge's (2013) Demons, Harry Shapiro's (2021) Fierce Chemistry and Jock Young's (1971) The Drugtakers. They might also be interested in my previous book on Drugs, Crime and Public Health: The Political Economy of Drug Policy (Stevens, 2011a).

When I read MacGregor's book, I was impressed by the depth of her description of drug policy fields at UK and international levels. But I was left unsatisfied by the conceptual tools she used to explain these policies, which are mostly based on methodological individualism. So I set out to provide an account which assumes that policy making is a collective endeavour. Policy outcomes are not just the aggregation of discrete, individual actions. To understand social processes, we need explanations that operate at the level of social groups. The theoretical precepts of critical realism provides such an understanding (Bhaskar, 1975; Archer, 2000). I present the policy constellation as a critical realist concept that I have developed to explain policy outcomes.

I developed this policy constellations approach in order to explain policy making in one field in one country. That field is drug policy. The country is the UK, which is made up of four separate nations with their own histories and relationships with controlled drugs. I try to reflect some of that national diversity by giving attention to drug policy in Scotland as well as at UK level. I hope that the policy constellations approach can also be applied to other policy fields and in other places.