Child Support Jurisdiction, Circuit Court, over the State

[EqualRights]

Does anyone know what state statutes, or Federal laws cover the Courts Jurisdiction over State Agencies?  I know it is illegal for the State of Illinois, through HFS to administratively garnish wages for amounts different than the pre-existing Child Support Order from the Circuit Court.  But I am not sure what specific statutes cover this.  I know due process is one, but what others