민법상 부당이득반환의 대상에 관한 연구

Korean Civil Code(KCC) stipulates in Article 748 the uniform effect that the ‘profit’ arising from the unjustified enrichment must be returned when the unified requirement of Article 741, ‘unreasonable acquisition of profit through another’s property’, is met, regardless of the type according to the process of unjust enrichment. And the profit is determined by the difference between the property situation that would have existed if there had been no unjust enrichment and the property situation due to the unjust enrichment (difference theory). Nevertheless, recently, a specific target theory has been asserted that the subject of the claim for the return of unjust enrichment is not the difference in property, but the return of the original property transferred as a reward. This view is based on a typology that distinguishes unjust enrichment by grant and unjust enrichment by infringement and recognizes different requirements and effects for each type, and is not valid in our civil law, which adopts the unified theory. In Germany, which recognizes the abstraction of real rights acts, unjust enrichment by grant and unjust enrichment by infringement show different aspects with regard to whether the recipient acquires ownership of the object. In the former case, if performance is made despite the invalidity of the bilateral contract, the ownership of the object is transferred to the recipient of the performance. Therefore, the recipient of the performance must return the ownership of the object under the unjust enrichment return principle, not the return of property law, and the other party must return the money received in return for the performance to the recipient of the performance. This situation of recovery by transferring the contract is very similar to the situation of performance by concluding a contract, so there is no major problem even if the legal principles of contract law are applied. On the other hand, in the situation of infringement of unjust enrichment where the ownership of the object is not transferred to the other party, the owner can exercise the right to claim return of the object, so the return of unjust enrichment principle is not applicable. The right to claim unjust enrichment arises only when such an object is destroyed or validly transferred to a third party and the resulting profit remains. However, in our civil law, this discriminatory situation of unjust enrichment by infringement and unjust enrichment by injury does not occur. Even in the case of unjust enrichment, the ownership of the transferred object is still held by the person who has made the transfer due to the inducement of the real right act, as in the case of unjust enrichment by infringement. In this case, the claim for return of the possession of the object and the claim for return of unjust enrichment for the consideration cannot have a relationship of connection due to the difference in the legal system of the two claims. Furthermore, there is no equivalence, which is the prerequisite for a relationship of connection, between the interest of possession that the recipient of the payment has in the object and the interest of consideration that the payment has in the object, so it is also difficult to say that they have a relationship of connection. The decisive reason why the theory of specific objects is insisted on in the German typology is because of the legitimacy and rationality of the principle of return of original object, which states that the ownership of the object should be returned to the former owner who lost the object due to the invalidity of the contract. However, in Korea, whether it is an unjust enrichment by infringement or an unjust enrichment by infringement, the rights of such owners are very well protected by real rights claims. The legal situation is completely different from that of Germany, where the return of the original object is recognized through the theory of specific objects in a situation of transfer of ownership due to performance of an invalid contract.