In light of the outcome of MA referendum question 4, which legalized possession of small amounts of marijuana for personal use, nonviolent drug offenders who have been prosecuted for marijuana possession should be freed from Massachusetts prisons, assuming their incarceration was due to possession of an amount of cannabis allowed under new state laws.
These people (who are, according to national statistics, disproportionately people of color)  are not a threat to Massachusetts residents, and, as such, should not be locked in cages for consuming a plant.
In addition to being freed, any mention of incarceration stemming from their possession of marijuana should be expunged from their criminal records, allowing them to more easily reintegrate into society.