Section 13-261.3. Retired employees; change of options

Notwithstanding any
  other provision  of  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 13-261 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  divorced  from  or  separated  pursuant  to  a
  judicial  decree from such spouse, then the board of trustees shall have
  the 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.