Over the past few decades, the landscape of foreign investment has undergone a paradigm shift, moving beyond purely profit-driven motives to integrate non-financial considerations into decision-making frameworks. This research addresses a critical tension: while traditional legal and economic systems often perceive compliance with environmental, social, and governance (ESG) standards as a financial burden, neglecting these requirements can lead to "creeping expropriation," violations of fair and equitable treatment, and heightened political risks. The study explores how non-financial requirements redefine the mutual rights and obligations of host states and foreign investors, and evaluates their impact on economic efficiency. Adopting a descriptive-analytical and quantitative-econometric methodology, the research utilizes the TOPSIS multi-criteria decision-making technique. The findings suggest that, contrary to traditional views, non-financial requirements serve as essential instruments for internalizing externalities and correcting market failures. From a legal perspective, the article examines the evolution of these standards in international instruments and their specific standing in Iranian law under the "public economic order" and Article 50 of the Constitution. Ultimately, the TOPSIS analysis demonstrates that