The paper addresses jurisdictional issues on the case of NSD initiating investment arbitration against Belgium/Luxembourg. Under the Russia-Belgium/Luxembourg BIT, the states undertake to prevent expropriation of investments and, if it does happen, to pay timely and fair compensation. Such “expropriation” may also occur due to sanctions. Being a Russian intermediate custodian for a number of foreign securities, the NSD has accounts with the centralized European securities Euroclear/Clearstream depositories. Since the inclusion of the NSD in the list of entities provided for in Annex I of EU Regulation no. 269/2014 in June 2022, transactions with the securities were suspended, NSD’s account with Euroclear/Clearstream was blocked. Because the NSD accounts with foreign securities depositories were blocked, it became impossible to transfer non-Russian securities from a securities account opened with the NSD to another Russian or foreign securities depository. One of the ways to challenge the consequences of Euroclear/Clearstream actions is to file a claim with the investment tribunal against Belgium/Luxembourg. The case has two potential solutions: mass claim from the end-investors or one single claim by the NSD as a “nominee holder” of the end-investors’ securities. The first option might seem time- and resource-costly, which is why a claim by the NSD might seem more attractive. Hence, using the interpretation instruments of public international law, the paper aims at assessing the perspectives of initiating investment arbitration proceedings by the NSD, thereby focusing on interpretation of the two central terms in the Russia-Belgium/Luxembourg BIT — “investor” and “investment”. The paper concludes that prima facie the investment tribunal would have jurisdiction over the case rationae personae nonetheless the “nominee holder” status of the NSD, as well as jurisdiction ratione materiae, where the blocked securities could constitute an “investment” in the sense of the BIT. Consequently, the paper defines the legal ...