50 USC 2111 - Recall

(a) Authority to recall 
The Director may, with the consent of a retired participant, recall that participant to service in the Agency whenever the Director determines that such recall is in the public interest.
(b) Pay of retired participant while serving 
A retired participant recalled to duty in the Agency under subsection (a) of this section or reinstated or reappointed in accordance with section 2051 (b)1 of this title shall, while so serving, be entitled, in lieu of the retired participants annuity, to the full basic pay of the grade in which the retired participant is serving. During such service, the retired participant shall make contributions to the fund in accordance with section 2021 of this title.
(c) Recomputation of annuity 
When the retired participant reverts to retired status, the annuity of the retired participant shall be redetermined in accordance with section 2031 of this title.
[1] So in original. Probably should be section “2051(c)”.