In a decade at UC Berkeley and seven years prior at the RAND Corporation, MacCoun has published widely on the topic of drug policy, including the book "Drug War Heresies: Learning from Other Vices, Times and Places" (Cambridge University Press, 2001), a study of the effects of Dutch cannabis coffee shops and other European drug policies (published in Science, 1997), and a study of street drug dealers (the RAND monograph "Money from Crime," 1990). He has served on various government advisory panels and given congressional testimony on the effects of drug laws on drug use.

Although he is a law professor, he is not a lawyer; he is a psychologist and a policy analyst. MacCoun's comments on medical marijuana: "I write as a policy analyst and social scientist, not as an activist. But my reading of the available evidence is that medical marijuana reduces suffering for patients with serious conditions who want to use it. What is far less clear is whether marijuana offers greater benefit than other drugs available to physicians. I also believe that medical marijuana, sensibly regulated, poses little risk of increasing the non-medical recreational use of marijuana. In terms of its actual relevance for American drug problems, medical marijuana is a sideshow. But it has enormous symbolic importance to partisans on both sides of the marijuana debate, which is why it has received so much political attention. There are genuinely difficult legal questions about federal versus state jurisdiction over drug use and drug sales. But the major purpose of the government's legal battle is to try to thwart what they fear is a slippery slope toward marijuana legalization."