The Human Rights Defence in International Investment Arbitration: Exploring the Limtis of Systemic Integration

In a variety of investment arbitration cases, respondent States have argued that the measure
complained of by the investor was mandated by the State’s human rights obligations. This defence raises intricate questions concerning the relationship between international investment law and human rights law. Tribunals have generally been reluctant to engage with the argument and to interpret the relationship between investment law and human rights in a straightforward manner. This article discusses two other possibilities: harmonious interpretation and prioritisation. Harmonious interpretation seeks to read provisions from investment treaties and human rights treaties together, whereas prioritisation gives normative superiority to one provision over another. We conclude that harmonious interpretation is facilitated by the discretionary character of common treaty standards in both human rights and investment law, but that the final result is not likely to be very different from prioritisation, because even harmonious interpretation requires that one provision is read in the light of, and thereby subjugated to, another provision.