The Financial Services Authority (FSA/OJK), as one of the supervisors in the transaction on Islamic Economic Institutions still faces problems in carrying out its duty and function optimally. This research aims to find the legal basis, mechanism, and method of law enforcement for disobedience of sharia compliance in the practice of Islamic financial institutions by FSA in Indonesia. This is a normative empirical research employs statutory and conceptual approach. The results of this study indicate that the legal basis, mechanism, and method of law enforcement for disobedience of sharia compliance in the practice of sharia financial institutions by FSA in Indonesia are based on sharia principles and prudential principles in operating the Sharia Financial Institution (SFI/LKS). The law enforcement mechanism is carried out by the FSA. Refering to Article 5-9 of the FSA Law, the authority of FSA is to ensure of sharia compliance of Islamic banking transaction by Islamic banking Institution.