For cannabis consumers who are accustomed to the black market's meager selection and iffy quality, Colorado's dispensaries are a revelation: dozens of strains, each with a distinctive bouquet, fresh enough that you can actually smell the difference. Denver-area budtenders, who say tourists account for half or more of their business, are used to amazed reactions, reminiscent of the scene in Moscow on the Hudson where Robin Williams, playing a Soviet defector, encounters an American supermarket for the first time. But once a visitor  settles on a gram of Budderface or a quarter-ounce of Cinderella 99, he has a problem: Where can he smoke it? State and local restrictions have made answering that question a much bigger challenge than it needs to be.

Amendment 64, which legalized marijuana for recreational use, prohibits consumption of cannabis on the premises of the state-licensed stores that sell it.