Prop 19 sticker  A sticker in San Francisco supports the passage
of California's prop 19 to legalize marijuana in 2010. State
voters rejected the measure, but a new version could resurface
during 2014 elections. See more controlled substance pictures.
© Mike Blake/Reuters/Corbis  Introduction to How Marijuana Works
Ganja. Bud. Herb. Call it what you will, there's no question
that marijuana has become a divisive issue in U.S. politics.
Whether for its role in supporting drug cartels, its tendency to
worsen the impact of unbalanced drug laws, or simply its
position in the center of the drug legalization movement, the
sticky icky has become a rather sticky wicket.  Although banned
by the U.S. government in 1937, marijuana has been the subject
of much legal wrangling since the 1980s, gradually opening the
way for medicinal use in 20 states and the District of Columbia
as of January 2014. Colorado and Washington also have approved
recreational use. Meanwhile, more than a dozen states have
decriminalized holding