The 6 November votes in Colorado and Washington left a lot of marijuana users happy and a lot of police officers nervous. And they set the two states up for a confrontation with the federal government, as marijuana is still illegal under federal law. Marijuana is the most widely used illicit drug in the US. Legalisation advocates say the recent votes mark the beginning of the end of the drug's prohibition. "It's a tipping point for sure," says Sanho Tree, director of the drug policy project at the Institute for Policy Studies.