In the Diallo case, the ICJ was required to answer the question of whether the Republic of Guinea could exercise diplomatic protection not only on behalf of its national, Diallo, but also on behalf of two corporations which were incorporated in the Democratic Republic of the Congo but which were owned by a national of the Republic of Guinea. While the Court decided, in line with Barcelona Traction, that the exercise of diplomatic protection for violation of direct rights of shareholders was admissible, it did not accept the claim on behalf of the companies ‘by substitution’. In its reasoning it took a rather restrictive view of the existing exceptions to the rule that protection can only be exercised on behalf of nationals.
