Notwithstanding any other provision of this chapter, the rights of each member to his or her accrued retirement benefits under the retirement system shall be nonforfeitable, in accordance with the requirements of Sections 401(a) of Title 26 of the United States Code that are applicable to public employee plans, to the extent then funded, on the date of the termination of the system, the partial termination of the system, or the complete discontinuance of contributions under the system, as provided in Title 26 of the United States Code.