As the Association of Southeast Asian Nations (ASEAN) becomes an influential actor in international investment rule-making, this article scrutinizes the environmental provisions within ASEAN investment agreements and evaluates their adequacy in preserving ASEAN member states’ (AMS) regulatory autonomy for environmental protection. Through a comprehensive survey of fifteen plurilateral investment agreements, the study conducts a comparative analysis with international treaty practices to determine the effectiveness of these provisions in reconciling environmental concerns with foreign investment promotion objectives. These findings reveal that environmental provisions in ASEAN investment agreements are often vague or narrowly tailored, limiting their ability to provide adequate regulatory space for AMS to implement necessary environmental measures. This article concludes by offering recommendations for enhancing environmental provisions in future ASEAN investment agreements to ensure a more balanced approach safeguarding both investment promotion and environmental regulation rights of AMS.

1. Introduction
2. ASEAN Investment Agreements: Intra-Region toExternal Plurilateral Agreements
3. Need to Incorporate Environmental Issues in ASEANInvestment Agreements
4. Types of Environmental Provisions in ASEANInvestment Agreements
    A. General Exception Clause
    B. Precluding Non-Discriminatory Regulation as a Basis for Claims of IndirectExpropriation
    C. Exceptions to National Treatment
    D. Expert Reports on Environmental Issues Requested by Investment Arbitration
5. Reserving State’s Right to Regulate Environmental Issues under ASEAN Investment Agreements
    A. Lack of an Overarching Principle
    B. Reference to Environmental Protection in the Treaty Preamble
    C. Provisions Strengthening States’ Right to Regulate Environmental Matters
6. Conclusion

• Kim Anh Dao(Ph.D. candidate in international law at Korea University; Lecturer at Law Faculty of Foreign Trade University (Vietnam).)