The Gist Mentions Mark Kleiman

There’s also another model promoted by the late Mark Kleiman, a great criminologist, who pointed out that you could do a great deal just in probation and parole by doing regular drug tests and saying to people, "there are sanctions and rewards for whether you use or not." If somebody tests negative, you say "you don’t have to serve the custodial part of your sentence," but then if they do test positive, you say, "ok, you’re going to have to have a single night in jail," which is not much for a population that’s often been in prison, but it’s a swift, certain, reliable penalty. That’s what motivates most people, and what motivates more so people who are addicted—during addiction it’s very hard to think about the distant future. "Maybe in ten years something bad will happen" is not as motivating as "you’re going to feel really good immediately if you use this drug."