Sovereign immunity, a cornerstone of international law, traditionally protects states from legal proceedings in foreign jurisdictions. However, in the realm of investment arbitration, this doctrine faces increasing tension as states enter into bilateral investment treaties (BITs) and multilateral agreements that allow private investors to initiate claims. This paper examines the evolving nature of sovereign immunity within the investor-state dispute settlement (ISDS) framework, focusing on the distinction between jurisdictional immunity and enforcement immunity. Through a comparative analysis of national court practices in the United States, United Kingdom, France, and Switzerland, it explores the complexities of enforcing arbitral awards against sovereign states. Highlighting key cases such as Letco v. Liberia and Micula v. Romania, the paper underscores the legal and practical hurdles in executing awards. The study concludes with proposals for harmonizing treaty language, adopting model enforcement laws, and fostering judicial cooperation to ensure a balanced approach that respects state sovereignty while maintaining the credibility and enforceability of investment arbitration.
