This is a good example of what is typically seen as racist at first glance, but if you look more closely it is not. You have to look at the whole picture.
Marijuana arrests and charges typically happen as a result of police interacting with someone for another reason. For example, a cop will get a description of a robbery suspect and stop someone as a result of a description match. They may stop a person who is innocent of the robbery but matches the description. If they find marijuana on that person, they can bring a charge. Since blacks tend to commit more crime, they have a higher rate of interaction with police. This is true of almost every type of crime your average street cop gets involved with. I'm not defending that practice and I 100% agree that it is not good policing, but it is also not racist.
If you want to find an example of drug enforcement that comes closer to "systemic" racism you'd have to go back to the 90s, when white people who were convicted of cocaine use were typically getting much lighter sentences than black people using crack. However, even in that situation there were extenuating circumstances. Usually blacks who got harsher sentences had a combination of aggravating factors like prior convictions, resisting arrest or violent behaviour.