It is quite common in investment arbitration for the respondent State to include in its defense to treaty claims one or more criticisms of the investor’s underlying conduct. Yet while such arguments feature prominently in State defenses, they are rarely framed as counterclaims seeking affirmative relief. The reason may lie in an instinctive preference by States to pursue any affirmative claims in their own courts. But it may also lie in perceived limits to the jurisdiction of international tribunals to hear State counterclaims.
Two recent ICSID decisions have reached entirely different conclusions on the issue of jurisdiction over State counterclaims. This essay touches briefly on certain jurisprudential and policy factors that may explain the divergent results and frame future cases for further analysis.