R.I. Gen. Laws § 45-21-62
Notwithstanding any other provision of the retirement laws of this state, any active member of the municipal employees' retirement system who was sixty (60) years of age or greater when their employment commenced, and commenced employment before June 22, 1989, and was ineligible by state law from joining the retirement system, is allowed to purchase service credits for actual past employment. The number of years for which credits may be purchased is limited to the difference between the date upon which they commenced employment at sixty (60) years of age or greater and June 22, 1989, when they were required by law to join the retirement system. Purchase of past service credits shall be at the rate that contributions would have been calculated at the time of past service, plus interest.
R.I. Gen. Laws § 45-21-62