The South Dakota Supreme Court has upheld a lower court's ruling that nullified a voter-passed amendment to the state constitution that would have legalized recreational marijuana use. Here, a cannabis plant at the Greenleaf Medical Cannabis facility in Richmond, Va., in June. Steve Helber/AP hide caption
U.S. Rep. Dave Joyce, R-Ohio, is co-sponsoring a GOP plan that would regulate marijuana like alcohol and enable the Department of Veterans Affairs to prescribe cannabis treatments to veterans. Mark Duncan/AP hide caption
An illegal cannabis cultivation site in the city of Buellton in Santa Barbara County, Calif. Authorities seized 20 tons of illegal cannabis in June in a raid that lasted four days. Santa Barbara County Sheriff via AP hide caption
A customer buys marijuana at Harborside dispensary in Oakland, Calif., on Monday. Mathew Sumner/AP hide caption
Kids who saw an ad for legal marijuana were more likely to report smoking it one year later, according to a Rand Corp. report. Tomas Rodriguez/Getty Images hide caption
Congress marijuana Bill Clark/CQ-Roll Call,Inc. via Getty Images hide caption
A man tends to marijuana plants at a 54,000-square-foot marijuana cultivation facility in Las Vegas. In Nevada's first weekend of recreational pot sales, "well over 40,000 retail transactions" were carried out, tax officials say. Ethan Miller/Getty Images hide caption
Proponents of the emerging pot-for-pleasure industry want to grab a share of the nearly $2 billion tourism business in Sonoma County with events like dinners that incorporate marijuana. Courtesy of Sonoma Cannabis Company/Kristen Jeanne hide caption
A demonstrator at a marijuana legalization rally in Washington, D.C., on Inauguration Day 2017. Theo Wargo/Getty Images hide caption
Cannabis plants grow in the greenhouse at Vireo Health's medical marijuana cultivation facility on Aug. 19 in Johnstown, N.Y. Drew Angerer/Getty Images hide caption
A marijuana plant is displayed during the 2016 Cannabis Business Summit & Expo last month in Oakland, Calif. Justin Sullivan/Getty Images hide caption
Kurt Britz checks a driver's license at the 3-D Denver Discrete Dispensary on Jan. 1, 2014, the first day recreational marijuana sales were legal in Colorado. Possession remains illegal for those under 21 years old, and statistics show a widening racial gap in arrests for those offenses. Theo Stroomer/Getty Images hide caption
A budtender prepares an edible sale for a customer at LivWell Broadway in Denver. Craig F. Walker/Denver Post via Getty Images hide caption
Two men inspect the goods at at Farma, a marijuana dispensary in Portland, Oregon. The state's first week of retail sales brought in an estimated $11 million, a trade group says. Josh Edelson/AFP/Getty Images hide caption