This study was motivated by the increasing number of criminalization cases against environmental activists who voice public interests, as seen in High Court Decision Number 374/Pid.Sus/2024/PT SMG. In this context, issues arise regarding the effectiveness of applying the principle of procedural justice through the Anti-SLAPP mechanism in providing fair legal protection. This research fills the gap in previous studies, which have primarily focused on substantive justice, neglecting the fair legal process as the core of procedural justice, despite procedural justice being a crucial pillar in protecting public participation. This study employs a qualitative method with a normative legal approach, examining relevant legislation, particularly Article 66 of Law No. 32 of 2009 on Environmental Protection and Management, as well as Islamic legal perspectives on protecting amar ma’ruf nahi munkar in environmental issues. The analysis focuses on the extent to which legal procedures in the case have reflected the principles of a fair trial, such as judicial impartiality, the defendant's right to defend themselves, and transparency in the legal process. The research findings indicate that the application of Anti SLAPP in the ruling still leaves several procedural issues that suggest potential violations of the principles of procedural justice. On the other hand, Islamic law emphasizes the importance of due process in law enforcement, making it relevant to enrich the framework for evaluating the implementation of positive law. Thus, this study contributes to critiquing and strengthening the aspect of procedural justice in legal protection for environmental activists from criminalization.