R.I. Gen. Laws § 27-20-16: Changing coverage.

No group health insurer subject to the provisions of this chapter shall change contract provisions as specified in the group plan master contract during the term of that contract without prior written agreement of the employer, except for changes mandated under state or federal legislative enactment and changes resulting from a labor/management collective bargaining agreement, or changes necessary to meet insurance regulations promulgated by the department of business regulation.