This article explores the conditions under which it is possible to bring claims based on non-international investment agreement ( IIA) norms of international law in investment treaty arbitration. For that purpose, it analyzes in the first instance broad dispute settlement clauses incorporated in IIAs that make reference to the settlement of 'any investment dispute'. Such clauses grant jurisdiction to investment treaty tribunals to hear non-IIA claims. However, at least two additional conditions need to be satisfied for the investor to bring a self-standing claim based on a non-IIA norm of international law. First, the non-IIA instrument ( a contract or another international treaty) may include a dispute settlement clause envisaging exclusive jurisdiction in favour of another forum. Second, the investor's standing to bring a claim based on a non-IIA norm of international law depends on whether this norm attributes any legal entitlement in the benefit of the investor.