An adjunct faculty member of a regional community-technical college or Charter Oak State College shall be permitted to irrevocably waive membership in a Connecticut retirement plan not later than sixty days after commencing employment with such regional community-technical college or Charter Oak State College. Once the adjunct faculty member waives membership in a Connecticut retirement plan, such faculty member is no longer eligible to elect to participate in a Connecticut retirement plan in any subsequent part-time employment with the regional community-technical college system, Charter Oak State College, the Board of Regents for Higher Education or any other constituent unit, as defined in § 10a-1.