신의성실의 원칙과 권리남용의 금지 - 대상판결: ‘사회통념상 합리성 법리’를 폐기한 대법원 2023. 5. 11. 선고 2017다35588, 35595(병합) 전원합의체 판결 -

The ruling actively utilized the prohibition of abuse of rights as a theoretical basis at abolishing the ‘legal principle of rationality in terms of social norms’ regarding unfavorable changes in the rules of employment and proposing the ‘legal principle of abuse of the right to collective consent’ as an alternative. However, the approach to prohibiting abuse of rights, that is, prioritizing either the employer’s right to change the rules of employment or the workers’ right to collective consent and prohibiting only the abuse of the exercise of that right as an exception, cannot realize the ideal of equal determination of working conditions. It is difficult to secure specific validity in individual cases. This is because it is the attitude of the Supreme Court to strictly examine whether or not there is abuse of rights. In order to reasonably adjust the various interests surrounding unfavorable changes in the rules of employment, it is necessary to request all parties involved in the act or procedure to act in good faith in the exercise of rights and fulfillment of obligations, rather than the legal principle of prohibition of abuse of rights with a conflicting structure. The principle of good faith should serve as a guiding principle. In this regard, the majority opinion that relied on the legal principle of prohibition of abuse of rights by abolishing the legal principle of rationality in social common sense, which is the legal principle that embodies the principle of good faith, and presenting the legal principle of abuse of the right to consent as an alternative, has fundamental flaws and limitations. Accordingly, as in the case of the Japanese Labor Contract Act, it is thought that a legislative solution can be an alternative solution by stipulating the legal principle of rationality and its judgment standards in the social common sense based on the principle of good faith.