Last summer in France, dozens of “CBD cafés” suddenly opened across the country. Exploiting a legal loophole originally created for hemp farmers, these pop-up businesses sold queuing customers oils, drinks and salves infused with cannabidiol, a cannabis compound that is a faddish if unproven “cure” for insomnia, anxiety and more. The French government reacted quickly and by mid-June had officially prohibited the sale of CBD. The CBD cafés vanished within a month. But France’s brief experiment with cannabidiol seems to have started a movement to legalize cannabis, which has been illegal since 1970.