Except for execution or withholding for the payment of child support or for the payment of spousal support for a spouse or former spouse who is the custodial parent of the child, contracts, benefits, and contributions under the university system retirement program and the earnings on the contributions are:
(1) exempt from any county or municipal tax;
(2) not subject to execution, garnishment, attachment, or other process;
(3) not covered or assessable by an insurance guaranty association; and
(4) unassignable except as specifically provided in the contracts.