Environmental Impact Assessment as Customary International Law in ASEAN Region: Some Legal Issues

In ASEAN region, while EIA is acknowledged as customary international law, its implementation varies in each country due to differences in historical backgrounds, legal status of the EIA, political motivations, and economic development priorities. This article examines the role of EIA as customary international law and EIA implementation in ASEAN member states to analyze challenges in EIA integration in the ASEAN region. It is concluded that the EIA implementation in the ASEAN region still faces several legal issues that need to be addressed. The key issues include the diversity of domestic legal framework, a lack of clear regulation and guidelines for public participation, insufficient political will and overlapping authorities, and traditional ASEAN cultures, particularly the “ASEAN way” or the principle of non-intervention among member states. Accordingly, ASEAN needs to enhance cooperation and adopt a unified approach to effectively integrate EIA practices, aligning them with regional environment and sustainable development goals.