10 U.S.C. § 1176: Enlisted members: retention after completion of 18 or more, but less than 20, years of service

A regular enlisted member who is selected to be involuntarily separated, or whose term of enlistment expires and who is denied reenlistment, and who on the date on which the member is to be discharged is within two years of qualifying for retirement under section 7314 or 9314 of this title, or of qualifying for transfer to the Fleet Reserve or Fleet Marine Corps Reserve under section 8330 of this title , shall be retained on active duty until the member is qualified for retirement or transfer to the Fleet Reserve or Fleet Marine Corps Reserve, as the case may be, unless the member is sooner retired or discharged under any other provision of law. the date on which the member is entitled to be credited with 20 years of service computed under section 12732 of this title ; or the third anniversary of the date on which the member would otherwise be discharged or transferred from an active status. the date on which the member is entitled to be credited with 20 years of service computed under section 12732 of this title ; or the second anniversary of the date on which the member would otherwise be discharged or transferred from an active status.