"As of January 2, possession of an ounce or less of marihuana or tetrahydrocannabinol (THC) will be a civil offense, punishable by a civil penalty of $100 and forfeiture of the marijuana under a new Section 32L of chapter 94C of the Massachusetts General Laws. Additional provisions apply to violators under the age of 18. Records of this new civil offense (a “Section 32L violation ”) will not be entered into the criminal offender record information, or “CORI,” system. "
We've linked to this and several other sources that explain or analyze the law on our new page, Massachusetts Law About Marijuana Possession.