A Mexican study says legalizing marijuana for recreational use in the US - an issue on the ballot in three US states - could cut the proceeds of Mexican drug gangs by 30 percent.
The International Cannabis & Hemp Expo outside Oakland City Hall this weekend includes a spot where medical marijuana cardholders can light up – another round in the fight over legalization.
By early 2014, some 20 US states and the District of Columbia had legalized the use of marijuana for medical purposes. In Nov. 2012, voters in Washington and Colorado passed initiatives to make their states the first in the country to allow recreational use of the drug. But under federal law, the sale of cannabis remains illegal. And the US Food and Drug Administration states that marijuana has "no currently accepted medical use in treatment in the United States." How much do you know about marijuana? Take our quiz and find out: