Massachusetts currently allows the sale of cannabis to both registered medical cannabis patients as well as adult-use cannabis consumers.
To shop, Massachusetts requires medical patients to be at least 18 years of age with a valid Massachusetts Medical Marijuana card and valid government issued photo ID, unless accompanied by a primary caregiver. They doesn't offer any reciprocity, so only in-state medical patients can shop the medical menu. Out-of-state medical patients must shop as adult-use.
Adult-use cannabis consumers must be 21 years of age with a valid government issued photo ID (in-state and out-of-state).
See also:
How do I obtain a Massachusetts Medical Marijuana Card?