As we circled the Denver airport, I could see the haze of cannabis smoke floating over the city—and almost smell it. But the Denver haze was certainly not marijuana smoke. As we would soon learn, although Colorado has legalized the recreational use of cannabis—smoking, eating, drinking, and absorbing (sublingually or transdermally)—it has also tightly regulated it. For one thing, you’re not allowed to smoke marijuana or hashish in public. Or in your car. Or use it in the same place where you buy the stuff—which effectively rules out cannabis restaurants and bars.