The development of the sharia economic sector in Indonesia has shown significant growth, yet it is accompanied by the increasing occurrence of defaults (wanprestasi) in the implementation of sharia contracts. The regulation of default in Indonesia generally refers to the Kitab Undang-Undang Hukum Perdata, which adopts a formalistic and contractual approach, thus not fully reflecting the principles of Islamic justice. Meanwhile, the Kompilasi Hukum Ekonomi Syariah incorporates sharia values; however, its regulation remains partial and lacks comprehensive legal certainty. This study aims to analyze the regulation of default in sharia contracts based on Islamic justice principles and to formulate the ius constituendum as a legal reconstruction for the future. This research employs a normative legal method with a literature study approach, analyzing statutory regulations, fatwas, and relevant legal doctrines. The findings indicate that the concept of default in Islamic law encompasses not only contractual breaches but also moral and ethical dimensions, including al-ta’addi (misconduct), al-taqshir (negligence), and mukhalafat al-syuruth (violation of agreed terms). Furthermore, compensation in sharia law (ta’widh) is limited to actual losses and excludes interest. Therefore, a legal reconstruction is necessary, focusing on the classification of default based on its causes, the standardization of compensation, and the strengthening of dispute resolution mechanisms through restorative justice approaches. This is expected to create a more just, proportional, and sharia-compliant legal framework for Islamic economic practices in Indonesia.