Section 12-125. Retired employees; change of options

Notwithstanding any
  other law to the contrary, no beneficiary shall be permitted  to  change
  any optional selection after it has become effective, provided, however,
  that if:
    (a)  a  retired  member  nominates  the  spouse  of such member as the
  survivor beneficiary under option two or three of section 13-177 of  the
  code,  or  if a retired member nominates the spouse of such member under
  option four of such section to receive payment of an annual benefit as a
  survivor; and
    (b) such person so nominated ceases by causes other than death  to  be
  his  or  her  spouse or is separated from such spouse; then the board of
  trustees shall have authority to  permit  the  change  of  the  optional
  benefit  to  the maximum benefit that is the actuarial equivalent by and
  with the consent of all parties.