Mo. Rev. Stat. § 525.160
Except as herein provided, no railroad corporation shall be required to make answer to any interrogatories propounded to it, in any action against any person to whom it may be indebted on account of wages due for personal services, nor shall any default or other liabilities attach because of its failure to so answer in such cases, where a writ of garnishment was issued or served in advance of the recovery by the plaintiff against the defendant, in any action for two hundred dollars or less; and any judgment rendered against any railroad corporation for its said failure or refusal to make answer to any garnishment so issued or served before the recovery of final judgment in the action between the plaintiff and defendant in the cases mentioned in section 525.150 shall be void, and any officer entering said judgment or who may execute the same shall be taken and considered a trespasser and in addition thereto may be enjoined by any court having jurisdiction; provided, this section shall not apply when the debt or claim sued for was contracted or accrued in this state; provided further, in such cases the petition or statement filed in the cause and the writ or summons of garnishment shall affirmatively show that the debt or claim sued for was contracted or accrued in this state and is owing to a bona fide citizen or resident of this state.
§ 525.160, RSMo