Section 1A. Any person residing in the commonwealth shall have the right to become a subscriber of a nonprofit hospital service corporation if the qualifications of such person meet those specified in the by-laws of such corporation; provided, however, that such corporation may, in its discretion, refuse to issue a subscription certificate to, or upon due notice, cancel the subscription certificate of any person who has made any fraudulent claim or representation to such corporation, or has been guilty of uncooperative or unethical dealings with such corporation, or has failed to pay dues and assessments seasonably and promptly, or for any other cause which may be approved by the commissioner. Any such corporation shall provide for annual open enrollment periods of not less than two months' duration. Proper notification shall be given to prospective subscribers in a form subject to approval by the commissioner.

All nonprofit hospital service corporations governed by this chapter which offer supplemental coverage to medicare, shall provide open enrollment for nongroup subscribers to medicare supplemental coverage, commencing on February first and ending March thirty-first of each year, for coverage to be effective June first of that year; provided, however, that nothing contained herein shall preclude additional periods of open enrollment for subscribers to medicare supplemental coverage.

Any person who is eligible for Medicare coverage for both hospital and physician services due to age or disability, other than end-stage renal disease, shall be eligible for supplemental coverage to Medicare ninety days before and after the month of such person's Medicare effective date or of the month of such person's loss of group or individual health coverage resulting from such person's retirement. Such supplemental coverage shall be effective no earlier than the effective date of Medicare coverage.