Soon after voters in Washington state passed Initiative 502 in November 2012, legalizing private recreational marijuana use by adults, smokers gathered at the Space Needle in Seattle to celebrate. Law enforcement officers indulged them, overlooking for an evening the fact that the law does not allow public consumption. Now the party's over, and legislators and others in Washington and Colorado, which passed a similar measure, are grappling with a number of legalization issues, including how to handle people who use marijuana and then drive.