The <i>rebus sic stantibus</i> doctrine in international investment law and ASEAN context: the case study of Vietnam

Purpose The paper aims to recommend that developing countries, such as Vietnam, should review and modernize bilateral investment treaties (BITs), strengthen their domestic legal frameworks, develop impact assessment mechanisms and enhance their capacity for dispute prevention to respond effectively to unforeseen changes in circumstances. Design/methodology/approach First, primary sources include the Vienna Convention on the Law of Treaties (VCLT), BITs, free trade agreements (FTAs) and arbitration awards from significant investment disputes. Secondary sources, including academic articles and commentaries from leading international law experts, are systematically analyzed to build a theoretical framework. The analysis of arbitration decisions focuses particularly on landmark cases, concentrating on cases concerning economic crises, political transitions and environmental policy changes to identify trends in the application of the doctrine. The paper provides a comparative analysis, contrasting Vietnam’s old BITs with newer agreements such as CPTPP and EVFTA to assess the development of treaty language related to exceptions and regulatory space. Findings The disparity between old-generation BITs and new ones (e.g. CPTPP, EVFTA) creates challenges in striking a balance between investment protection and policy space for environmental, health and sustainable development. Research limitations/implications The research mostly combines analysis of Vietnam’s specific economic, environmental and political context for future application of the rebus sic stantibus doctrine. Practical implications Understanding and effectively applying the doctrine of rebus sic stantibus is crucial. From this approach, countries can develop effective mechanisms to respond to economic and social changes without violating their international obligations. Besides, developing countries may require emergency measures affecting foreign investment, such as the temporary requisition of private property, restrictions on the export of essential medical supplies or the imposition of new safety and environmental regulations. Social implications Implementing policies to protect public interests and sustainable development; the general trend in investment law worldwide is a shift toward a sustainable approach linked to governance and environmental objectives. Originality/value For developing countries like Vietnam, studying this doctrine holds significant and practical importance.