Federal law bans all marijuana but, in 16 states and Washington, DC, it's legal as medicine. As a candidate, Barack Obama said he would not "circumvent state law," and his administration discontinued the high-profile raids of the Bush years. But now those raids have resumed, and local officials implementing state laws are being threatened with federal prosecution. Has the President broken a campaign promise? Is medical marijuana a front for organized crime? Is it so widely used that the federal ban should go the way of alcohol prohibition?