The White House on Thursday formally reclassified state-licensed cannabis as a “Schedule III substance,” paving the way for the Food and Drug Administration to study its medicinal uses. For over a half-century, the drug was listed under the U.S. Controlled Substances Act as a Schedule I substance, a list that includes heroin, ecstasy and peyote. The reclassification, however, does not legalize marijuana for medical or recreational use under federal law.