歐、美、日等先進國家，對於「通姦」之行為，均以除罪化相因應。我國刑法第239條通姦及相姦罪之制定，對於婚姻關係存續中，配偶與第三人之性行為處以刑事制裁，對人民之性自主權，利用公權力加以限制，是否違憲？本研究針對此問題提出全盤之檢討，認為通姦行為並未對其他個人發生實質上法益損害或危險，僅屬婚姻契約上忠實義務之違背問題；其次，通姦罪之法定刑
只是一年以下有期徒刑，在刑事司法實務上，通常不會判超過六個月，而且可以易科罰金，其嚇阻作用甚小；再者，對通姦罪之取證，因為本罪不罰未遂犯，除非被告承認犯罪，否則，在舉證責任上，要證明被告犯罪，其困難度很高。所以，通姦罪既無具體之保護法益存在，刑罰規範之內容即欠缺合憲性、必要性及正當性，在憲法原則之要求下，應無刑法之效力。因此，刑法第239條顯然違反憲法第23 條之規定，應屬無效，何況，其懲罰對象又衍生出另一個性別不公之問題，實有必要予以除罪化。

America, Japan and countries in Europe have decriminalized adultery.
Article 239 in the criminal code of Taiwan establishes that duringa marriage,a spouse engaging in sexual acts with a third party will be penalized for adultery. Is this code unconstitutional in its use of public power to limit the people's sexual rights? This study discusses all facets of the issue. This study holds that adultery breaks the contract of fidelity in a marriage agreement,and this does not cause essential damage or danger to the rights of other individuals.
Additionally, the statutory punishment for adultery does not pose much threat with a sentence less than one year and common judiciary sentence
less than six months with a transferable monetary fine. Also, non-penetration or attempts are not punishable; it is difficult to acquire evidence provingthe accused guilty unless the accused admits to the crime. Criminalization of adultery does not specifically protect legal rights, and the penalty lacks constitutionality,necessity and validity; under the principles of constitution, this penalty should not be in effect. This is why article 239 of criminal code violates article 23 of the constitution and should be considered void. In addition, this also brings up the issue of unequal punishment contingent upon the gender of the accused; to avoid these pitfalls the decriminalization of adultery is a necessity.