Amber McGowan, left, and Krystal Klacsan work Monday at Cannabis City in Seattle, a day before the store is to begin legal pot sales on Tuesday. The store will be for now the only one in Seattle to sell recreational marijuana.
Ted S. Warren/AP
People smoke marijuana, presumably, because it affects their brains, not despite that fact. Above, people in Sao Paulo, Brazil, campaign for the legalization of marijuana.
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Former Supreme Court Associate Justice John Paul Stevens likens making pot illegal to Prohibition. In his new book, Six Amendments, he proposes constitutional changes including a curb on an individual's right to bear arms.
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The legalization of marijuana could dry up a revenue stream for police, according to reports. Here, two men share a water pipe underneath the Space Needle shortly after a law legalizing the recreational use of marijuana took effect in Seattle in 2012.
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This dead juvenile coho salmon was found in a tributary of California's South Fork Eel River. About 20 large-scale marijuana farms are located upstream from the watershed pictured. All of them divert water from the stream.
Courtesy Scott Bauer
A man uses the Nasal Ranger to detect smells in the southern U.S., in this photo provided by St. Croix Sensory. In Denver, the device is being used to monitor complaints of strong marijuana smells.
Courtesy of Nasal Ranger