My research explores a struggle for truth and justice waged by Tamil family members of the disappeared during the last phase of Sri Lanka’s civil war (1983-2009), the vast majority of them women. Conceptualising this struggle, increasingly waged at the UN Human Rights Council in Geneva, as a subaltern, dissident, and transnational struggle against impunity, I ask how does the postcolonial Sri Lankan state defer accountability and entrench impunity for mass atrocity in the age of universal human rights? How do we understand impunity for mass atrocity? What is at stake in such struggles?  How do victim survivors of war challenge impunity?  Why is truth and justice so elusive, even where there appears to be political will to address demands for justice? And what are the limits and possibilities of internationalised justice? Taking an interdisciplinary, intersectional feminist approach, and drawing on anthropology, law, and political science, I grapple with these questions based on a multi-sited ethnography conducted in Sri Lanka and Switzerland. This research conceptualise impunity not merely as a breakdown of the rule of law or a state of legal exception, but as an extra-legal phenomenon entangled with hegemonic, Sinhala Buddhist majoritarian nationalist conceptions of the nation and its postwar nation building project. I argue that what is at stake in the postwar struggle for justice in Sri Lanka is not merely questions relating to guilt or innocence or amnesty or punishment, but national identity, and nationalist visions of who is included and excluded within the nation. In demanding for truth and justice for disappearances, I contend that the women next of kin of the disappeared are posing a radical challenge to the postwar Sinhala Buddhist nationalist nation building project itself.