Federal law prohibits the use of marijuana, even as medicine. In his first term, President Obama suggested that states might legalize it without federal interference but, then, the Justice Department cracked down in California and elsewhere. Last month, voters in Colorado and Washington State legalized all uses of marijuana. The President's made no secret that he, himself, used marijuana as a young man. Last night in an interview for ABC's 20/20, Barbara Walters asked if he thinks marijuana should be legalized. Ethan Nadelmann is Director of the Drug Policy Alliance, a New York group advocating reform.