Substance use can cause harms to individuals and societies, but opinions differ regarding how these harms are best reduced. Such opinions will also reflect how we view trade-offs, as policies need to balance the harms of use against negative consequences of restrictive policies and the pleasures and benefits that the majority of users may claim to experience. Over time, and across regions, policies – even for the same substance – have ranged from strict prohibitions criminalising production and consumption to relatively unregulated commercial markets. In recent years, policy changes in US states, Uruguay and Canada have fuelled a growing debate on whether cannabis supply and consumption should be legalised and, if so, how strictly it should be regulated (Caulkins & Kilmer, 2016; Hawken, Caulkins, Kilmer, & Kleiman, 2013; Room, 2014; Uchtenhagen, 2014). The appropriate balance between “free market” and “government control” also remains an issue for alcohol, with a current example being the debate over minimum unit pricing (Holmes et al., 2014; Stockwell, Auld, Zhao, & Martin, 2012). Public health arguments are frequently emphasised in these discussions (Hall & Degenhardt, 2009; Hall & Lynskey, 2016; Room, Babor, & Rehm, 2005) with a particular focus on adolescent use (Hasin et al., 2015; Simons-Morton, Pickett, Boyce, ter Bogt, & Vollebergh, 2010), while other concerns include social consequences (Klingemann & Gmel, 2001; Laslett et al., 2011) and crime and criminalisation (Csete et al., 2016a; MacCoun & Reuter, 2001).