契約上 共通의 錯誤에 관한 연구

Mutual Mistake in Contract

The issue of mutual mistke in contract became a controversial topic in Korea recently. The Korean Supreme Court has been dealing with this issue in two ways. In some cases, mutual mistake was recognized as a ground of avoidance of contract. In other cases, the court opined that the contract can be adapted to what might have been agreed had the mistake not occurred. The views of the commentators are divided. Some assert that mutual mistake cannot be a ground of avoidance, but only termination of contract should be allowed. If other party is willing to perform the obligation as the party who wishes to end the contract has expected, however, the contract remains valid. This theory is based on the “Lehre der Geschäftsgrundlage”(a modified form of the clausula rebus sic standibus doctrine) originated from Germany. Others insist that the adaptation of contract is possible by way of the constructive (supplementing) interpretation, but the avoidance of contract should not be permitted. Still others believe that there is no reason not to allow the avoidance, but this should be an ultima ratio when the adaptation of the contract by way of constructive interpretation is not possible. From the comparative perspective, many jurisdictions recognize the avoidance of contract based on mutual mistake. Meanwhile, there are some jurisdictions in which the avoidance is the last resort when the adaptation cannot be achieved. Recent international model rules such as PECL and DCFR have followed the latter path. In my opinion, this “adaptation first, avoidance next rule is the best method to deal with the issue of the mutual mistake. Constructive interpretation functions as the theoretical basis of the adaptation. This rule enhances economic efficiency as well.