Mo. Rev. Stat. § 454.1710: Modification of convention child support order.

(a) A tribunal of this state may not modify a Convention child support order if the obligee remains a resident of the foreign country where the support order was issued unless:

(1) the obligee submits to the jurisdiction of a tribunal of this state, either expressly or by defending on the merits of the case without objecting to the jurisdiction at the first available opportunity; or

(2) the foreign tribunal lacks or refuses to exercise jurisdiction to modify its support order or issue a new support order.

(b) If a tribunal of this state does not modify a Convention child support order because the order is not recognized in this state, section 454.1701(c) applies.