The purchase of marijuana has been legalized in Colorado; it is not legal however to smoke grass in public. There was a huge festival in Denver today to celebrate that ownership is legal, and even though there were many (police) warnings about public use, by mid afternoon there was a noticeable blue cloud over civic park.
It was another subculture to enjoy. If you care to inhale further, do check out Flickr.
BTW, I don't blip dogs often (or at all) but this chap made the photo for me. No idea whether he was trained to sniff for marijuana or not.