Like many international tribunals, the International Court of Justice subscribes heavily to the principle of free admissibility of evidence. Neither its statute nor rules impose substantive restrictions on the admissibility of evidence, whether by way of exclusionary rules or an exclusionary discretion. Instead, the court’s practice has been to focus on evaluating and weighing the evidence after it has been admitted. There are certainly features of the ICJ that sets it apart from domestic courts and arguably justify such an approach: the ICJ is for settling disputes between sovereign states; it does not use a typical fact-finding system; its rules and practices reflect a mix of civil and common law traditions; and traditional exclusionary rules were not conceived with inter-state dispute resolution in mind. Yet for any judgment to have legitimacy, the evidential foundations must be strong and there should be a coherent and principled mechanism to sieve out problematic evidence at an early stage. Having this mechanism can also ensure that resources are not wasted and rights protected. Through an examination of the court’s rules and jurisprudence and the rules and practices of other international tribunals, this article makes the case for the codification of a provision that gives the ICJ an exclusionary discretion.