Over half of EU countries, as well as the United States and Canada, ban the stimulant qat, a sort of mild amphetamine. But attempts to do so in Britain, most recently in 2005, left experts unconvinced that the stuff was so harmful to mind, body or society that dealing in it should be made a crime. Thinking may now be changing. Is banning qat the right move? Probably not. It has not broken into the mainstream.