10 USC 1449 - Mental incompetency of member

(a) Election by Secretary Concerned on Behalf of Mentally Incompetent Member.— 
If a person to whom section 1448 of this title applies is determined to be mentally incompetent by medical officers of the armed force concerned or of the Department of Veterans Affairs, or by a court of competent jurisdiction, an election described in subsection (a)(2) or (b) of section 1448 of this title may be made on behalf of that person by the Secretary concerned.
(b) Revocation of Election by Member.— 

(1) Authority upon subsequent determination of mental competence.— 
If a person for whom the Secretary has made an election under subsection (a) is later determined to be mentally competent by an authority named in that subsection, that person may, within 180 days after that determination, revoke that election.
(2) Deductions from retired pay not to be refunded.— 
Any deduction made from retired pay by reason of such an election may not be refunded.