DALY CITY, CA – APRIL 18: Leaves of a mature marijuana plant are seenin a display at The International Cannabis and Hemp Expo April 18, 2010 at the Cow Palace in Daly City, California. The two day Cannabis and Hemp Expo features speakers, retailers selling medical marijuana smoking paraphernalia and a special tent available for medical marijuana card holders to smoke their medicine. Voters in California will consider a measure on the November general election ballot that could make the State the first in the nation to legalize the growing of a limited amount of marijuana for private use. (Photo by Justin Sullivan/Getty Images)