(d) An employee who is separated from the service, except by removal for cause on charges of misconduct or delinquency—
(1) after completing 25 years of service as a law enforcement officer, member of the Capitol Police or Supreme Court Police, firefighter, nuclear materials courier, or customs and border protection officer, or any combination of such service totaling at least 25 years, or
(2) after becoming 50 years of age and completing 20 years of service as a law enforcement officer, member of the Capitol Police or Supreme Court Police, firefighter, nuclear materials courier, or customs and border protection officer, or any combination of such service totaling at least 20 years,
is entitled to an annuity.