Any participant who is at least 50 years of age and has 20 years of creditable service, including at least 5 years of service credit toward retirement under the System (excluding military and naval service), may on his or her own application and with the consent of the Secretary be retired from the Service and receive retirement benefits in accordance with section 4046 of this title. The Secretary shall withhold consent for retirement under this section by any participant who has not been a member of the Service for 5 years. Any participant who voluntarily separates from the Service before completing 5 years in the System and who, on the date of separation, would be eligible for an annuity, based on a voluntary separation, under section 8336 or 8338 of title 5, if the participant had been covered under the Civil Service Retirement System rather than subject to this subchapter while a member of the Service, may receive an annuity under section 8336 or 8338, notwithstanding section 8333(b) of title 5, if all contributions transferred to the Fund under section 4045(c)(1) of this title