權利失效根源於誠信原則及信賴保護，係權利濫用的下位類型，乃典型德國法官造法所形成的制度，理論發展已超過一百年，在比較法上為台灣實務所繼受，亦將近五十年。在法律政策上是為修正消滅時效期間過長之嚴苛性，乃是「一種特殊不得已的救濟方式」，具有「例外性格」，只有在極端例外情形才有其適用，以免架空消滅時效制度。此點為台灣實務判決上所忽略。本文認為，權利失效之客體雖然包括私法上之一切權利，但在台灣法的解釋上，其適用對象應不包括「已登記不動產的所有物返還請求權」，以免架空物權之效力，破壞大法官釋字第107號及第164號解釋宣示已登記不動產之所有物返還請求權無消滅時效適用之憲法效力。在法院實務上，最高法院過度寬認權利失效在所有物返還請求權之適用，已造成所有權人的所有權被掏空之現象，有重新檢討之必要。

Forfeiture (Verwirkung) originates from the principle of good faith and the protection of reliance interest, and it has become a secondary type of abuse of rights. It's a system which is typically cultivated by the German judge-made law and has gone through the theoretical development of more than one hundred years. From the view of comparative law studies, it has been accepted in Taiwan's judicial practices for nearly half a century.The legal policy of forfeiture is aimed to correct the strictness of extinctive prescription, in which the period is too long, and to be a ”special remedy as a last resort”. With its ”exceptional character”, forfeiture should be applied only in exceptional cases in order not to make the system of extinctive prescription useless. However, this regard has been ignored by Taiwan's court.This article points out that although the objects of forfeiture include all rights in the private law, it should not be applied to the right of claim on registered real property under the interpretation of Taiwanese law. It is to avoid the erosion to the right of property, and not to destroy the binding effect of interpretations No.107 and No.164 of Justices of the Constitutional Court, which have emphasized that the rules of extinctive prescription should not be applied to the right of claim on registered real property. In the judicial practices, it is necessary to review the decisions of the Supreme Court, which have recognized the application of forfeiture to the right of claim in an excessively wide range and have resulted in the unjust loss of property owners.