Why is the california welfare dep. taking money our of my pension?

my father has been going to court for 10 years with the san diego welfare department for child support or at least when he didnt pay it and his ex-wife was on welfare they at first they told him he owes 36,000 dollars once he paid that they took him to court so he got a lawyer and made it so supposedly it would be the last case and they couldnt hide anything from him after that case so at the end of the case it was announced that total he owes now 90,000 dollars so he said fine as long as there will be no more about this in the future ect. well this morning my father found out that san diego's welfare department dug into his retirement and took $8,000. this case should be over hes paid california more than deserved by far.. my question is how can we make this finally come to an end and stop the harment.