(a) An employee who elects NAFI retirement system coverage with credit for FERS service under §847.431(a) is excluded from coverage under FERS during that and all subsequent periods of employment, including any periods of service as a reemployed annuitant.

(b) FERS service which becomes creditable in a NAFI retirement benefit based on an election under §847.431 is not creditable for any purpose under FERS.