Prior to the rise of international investment treaties and institutionalization of investor–state arbitration, the protection of foreign investors from mistreatment in the host state courts was the preserve of customary international law, which prohibited a denial of justice and provided for diplomatic protection as a principal means of dispute settlement. In contrast, contemporary international investment law offers a whole array of legal standards that can be invoked in seeking redress for the acts of national courts before international arbitral tribunals. In addition to relying on the customary prohibition of denial of justice, investors can challenge judicial conduct under the treaty standards on expropriation, fair and equitable treatment and, in some cases, the obligation to ensure effective means of asserting claims. Although the multiplicity of standards available to aggrieved investors can be regarded as an inalienable part of an effective regime for the protection of foreign investment, it also gives rise to a number of fundamental problems relating to the application of procedural mechanisms designed to control the review of the conduct of national judiciary by international courts and tribunals. Focusing on arbitral cases in which claims of a denial of justice were brought under the rubric of ‘a judicial expropriation’ and ‘a failure to provide effective means of asserting claims’, this article seeks to ascertain when investor claims relating to the administration of justice in the host state courts become amenable to arbitral scrutiny. It argues that, by providing a variety of standards under which the acts of judiciary can be challenged, investment treaty law allows investors to circumvent procedural barriers and thus muddles the boundaries demarcating the scope of international review of national judicial conduct.