Mass. Gen. Laws ch. 32B, § 24

An appropriate public authority of a political subdivision which has undertaken to provide health insurance coverage to its subscribers under this chapter may provide health care flexible spending accounts to allow certain subscribers, as determined by the appropriate public authority, to set aside a portion of earnings to pay for qualified expenses which may include, but shall not be limited to, out-of-pocket costs such as inpatient and outpatient copayments, calendar year deductibles, office visit copayments and prescription drug copayments.