. >> in a virginia courtroom, on that same day, harry kelso faced a very different kind of fate. >> itesident. and i got ten years on weed, a first charge. >> reporter: the 25-year-old was sentenced to prison for conspiracy to distribute marijuana and three counts of encouraging a minor to assist in distribution. >> it was like 17 and 10 months, and they in turn sold it to a confidential informant. >> african-americans, despite having virtually indistinguishable rates of usage between black americans and white americans, are nearly four times as likely to be arrested for cannabis use as their white peers. >> reporter: marijuana wasn't always policed this way. for hundreds of years, cannabis wasn't regulated at all. >> it's not really until the late 1930s when cannabis bans begin to be put in place. >> it was associated with mexican immigrants and then african-american entertainers and sharecroppers in the american south. >> treasury department intends to pursue a relentless warfare. >> we see the head of the federal bureau of narcotics, harry ence linger, have a concerted vendetta agai