〈Case in which a custodial parent of foreign nationality claimed past child support from a non-custodial parent of Korean nationality for the period prior to the finality of a judgment of acknowledgment of paternity〉

【Holding】

[1] In a case involving foreign elements, whether the court has a duty to examine and investigate the governing law under the applicable international convention or the Act on Private International Law even where no assertion has been made regarding the governing law (affirmative)

[2] Where only one of the parents has come to raise the child, whether the custodial parent may claim reimbursement of past child-rearing expenses to the extent that it is deemed reasonable for the other parent to share them (affirmative) / The standard for determining the scope of such sharing in that case / Whether reimbursement of past child-rearing expenses incurred prior to the finality of a judgment of acknowledgment of paternity may also be claimed to the extent that it is reasonable for the other parent to bear them (affirmative)

【Summary of Order】

[1] Foreign law that applies as the governing law to a legal relationship involving foreign elements is law, not fact, and the court must investigate its contents ex officio. Therefore, in a case involving foreign elements, even where no assertion has been made regarding the governing law, the court has a duty to examine and investigate the governing law under the international convention or the Act on Private International Law applicable to that legal relationship, such as by actively exercising its right of clarification to give the parties an opportunity to state their opinions or to have them submit the necessary materials.

[2] Parents are jointly responsible for raising the children born to them, and the expenses required for child-rearing must, in principle, be borne jointly by the parents; this is an obligation arising from the very nature of the parent-child relationship, regardless of which parent exercises parental authority, which parent has custody, and which parent is actually raising the child. Where, for whatever reason, only one of the parents has come to raise the child, except in cases involving special circumstances, such as where such unilateral rearing arose from the custodial parent's one-sided and selfish purpose or motive, or is not beneficial to the interests of the child, or where imposing the child-rearing expenses on the other parent would rather be contrary to equity, the parent who is raising the child may not only claim from the other parent a share of an appropriate amount of the present and future child-rearing expenses, but may also, since the parents' duty to raise their children arises, absent special circumstances, simultaneously with the birth of the child, claim reimbursement of past child-rearing expenses where it is deemed reasonable for the other parent to share them.

However, if all of the past child-rearing expenses incurred before the custodial parent's claim for child support were imposed on the other parent, the other parent would have to bear, at once, child-rearing expenses that the other parent had not anticipated, which would be excessive and harsh and might be contrary to the principle of good faith or the principle of equity; therefore, in such a case, it is not necessarily required to determine the amount by the same standard as child support after the demand for performance, and the court may determine the scope of sharing that is deemed appropriate, taking into account various circumstances such as the circumstances under which one of the parents came to raise the child and the amount of expenses incurred therefor, whether and when the other parent became aware of the duty of support, whether the expenses were ordinary living expenses required for child-rearing or exceptional and unavoidable large special expenses (such as medical expenses), and the parties' financial situations, economic capacities, and the equity of the burden.

Article 860 of the Civil Act provides that "acknowledgment shall take effect retroactively from the time of the birth of the child." Therefore, although the legal duty of support materializes upon the finality of a judgment of acknowledgment, the parents' legal duty of support, once the judgment of acknowledgment becomes final, takes effect retroactively from the time of the child's birth; accordingly, the custodial parent must be regarded as being able to claim reimbursement of past child-rearing expenses incurred prior to the finality of the judgment of acknowledgment as well, to the extent that it is reasonable for the other parent to bear them.

【Referenced Statutes】

[1] Articles 1 and 18 of the Act on Private International Law; Article 134 of the Civil Procedure Act [matters to be examined ex officio] [2] Articles 837, 860, and 864-2 of the Civil Act

【Referenced Precedents】

[1] Supreme Court Decision 89Daka20252, April 10, 1990 (Gong 1990, 1043)
Supreme Court Decision 2016Da222712, December 24, 2019 (Gong 2020Sang, 332)
[2] Supreme Court Order 92Seu21, May 13, 1994 (en banc) (Gong 1994Sang, 1693)
Supreme Court Order 2015Seu471, December 28, 2018

(Source: Supreme Court Order 2023Seu643, October 31, 2023 [Child Support] > Comprehensive Legal Information System, Precedents)