The Athletic's Ken Rosenthal reports that, as part of MLB and the MLBPA's recent agreement on a treatment program for opioids, the league will also remove marijuana from the list of banned substances for minor leaguers. As Rosenthal notes, major league players aren't tested for marijuana but minor leaguers are.
Though the use of medicinal marijuana has been decriminalized in most of the U.S., the drug remains illegal at the federal level. It is classified as a Schedule I drug along with other substances such as heroin, peyote, and ecstasy.
It is great to see the league being forward-thinking on this particular issue. The messaging on marijuana has, for decades, been misleading. As a result, the drug grew a reputation it didn't deserve. In this day and age, many players use or have used the drug without it having a major impact on their lives. In many cases, the impact is positive. Former Astros first baseman Jon Singleton remains a well-known outlier. Furthermore, testing for and thus having to punish players for the use of marijuana removes any incentive for the player to be honest and seek help if the drug impacts their lives negatively. This, along with the opioid program, hopefully results in players feeling comfortable enough to seek the help they need if they need it.