Absolutely a criminal justice issue. Its an economic issue ("unemployable" people gravitate towards black market labor roles). Its a health care issue (street drugs often stand in for prescription medication, particularly pain relievers and psyche meds). Its a color-line issue (drug use becomes an ethnic stereotype which is used as an excuse to segregate).

All these tail effects make explicit prohibition more of a problem than a solution. Tackling the associated problems - health care needs, jobs program, desegregation - goes a long way towards reducing the incentives to consume (and therefore distribute) harmful substances.