The arbitrary deprivation of dual nationality in investment arbitration

Abstract Recently, some investment tribunals have held that the doctrine of ‘effective and dominant nationality’ is a ‘relevant rule of international law’ according to which dual nationals can only invoke the protection of the respective bilateral investment treaty to the extent that they invoke their effective and dominant nationality to sue the State of their non-dominant nationality. However, the idea that multiple nationalities are an evil that must be avoided in the interest of States has ceased to be valid. In 1960, less than a third of states accepted dual nationality. By 2018, three-quarters of states allowed their nationals to possess another nationality. We are currently witnessing a paradigm shift that some arbitrators are still reluctant to acknowledge. When an investment tribunal claims to apply the ‘effective and dominant nationality principle’ what it is actually doing is refusing to recognize one of the claimant’s nationalities. The non-recognition of a nationality that does not correspond to an express legal norm and does not respond to a legitimate purpose is arbitrary and, therefore, should be prohibited as it violates a fundamental human right.