比例原則在國際投資仲裁中的適用反思：場域邊界與規範張力

Reflection on the Application of Proportionality Principle in International Investment Arbitration: Field Boundary and Normative Tension

比例原則廣泛適用於國際投資仲裁實踐，保護了外國投資者的權益，但這並不能否認其適用於國際投資仲裁存在理論薄弱、根基不穩的脆弱性。從合法性看，對源自國內行政法的比例原則，仲裁庭並未清晰闡明其在國際投資仲裁法律體系中的法源定位，國內法和國際法的場域邊界造成該原則在國際投資仲裁中的適用存在合法性障礙。從合理性看，仲裁庭適用比例原則時參照了人權法院的判例，但因缺乏與人權法院等效的環境要素，導致規範效果難以契合投資仲裁的需求。針對比例原則在國際投資仲裁適用中面臨的雙重困境，東道國可以考慮在對外簽訂投資協定時明確規定比例原則的適用模式或引入相關利益優先條款。仲裁庭在適用比例原則裁判時則需要綜合考量東道國的社會背景，避免過於主觀的價值評判。

The principle of proportionality is widely applied in the practice of international investment arbitration, which protects the rights and interests of foreign investors, but it cannot be denied that it has weak theoretical reliance and unstable foundation when applied to international investment arbitration. From the point of view of legality, the arbitral tribunal did not clarify its legal source position in the legal system of international investment arbitration, and the field boundary between domestic law and international law caused legal obstacles in the application of this principle in international investment arbitration. From the perspective of rationality, when applying the principle of proportionality, the arbitral tribunal referred to the precedents of the Human Rights Court, but due to the lack of environmental elements equivalent to those of the Human Rights Court, the normative effect could not meet the demands of investment arbitration. As to the double dilemma faced by the principle of proportionality in the application of international investment arbitration, the host country can take into consideration clearly stipulating the application mode of the principle of proportionality or introducing relevant interest priority clauses when signing investment agreements with foreign countries. When applying the principle of proportionality, the arbitral tribunal should comprehensively consider the social background of the host country and avoid over-subjective judgment of value.