得利丧失抗辩修正问题研究

Research on Modification of the Defense of Eliminated Enrichment

摘要: 在双务合同无效后的不当得利返还上若一方当事人得利客体毁损灭失无法返还，学说上主要发展出差额说、财产决定说和对待给付返还说修正该类案型下的返还关系。差额说主要修正无效后返还中的风险分配，财产决定说和对待给付返还说相比差额说更进一步，主要以不得自相矛盾的原则为论证逻辑。虽然一定程度上能够达到双务合同无效后返还双方的利益平衡的目的，但是上述学说的必要性和正当性似有不足。得利丧失抗辩是不当得利制度中的例外规则，适用例外规则需要谨慎，而主张例外的例外则更需要慎重。

Abstract: In terms of the return of unjust enrichment after the invalidity of the two-service contract, if one party cannot return the damage and loss of the object of profit, the doctrine mainly develops the theory of the balance, the property decision and the return of treat-ment to amend the return relationship under this type of case. The balance theory mainly corrects the allocation of risks in the return after the invalidation, and the property decision theory and the return of treatment of payments are further than the balance theory, mainly based on the principle of non-contradiction as the argument logic. Although to a certain extent, it can achieve the purpose of returning the balance of interests between the two parties after the invalidity of the dual-service contract, the necessity and legitimacy of the above doctrine seem to be insufficient. The defense of eliminated enrichment is an exception rule of unjust enrichment system, and the application of the exception rule requires caution, while the exception that asserts the exception requires even more caution.