In stark contrast to its typical disinclination to engage with the case law of other courts and tribunals, the International Court of Justice has shown a remarkably consistent attitude of deference towards specialised courts and tribunals the last two decades. That trend was, however, disrupted in 2021 in the judgment rendered in Qatar v. U1E where the Court explicitly rejected the interpretation provided by the Committee on the Elimination of Racial Discrimination according to which nationality-based differential treatment can, in some circumstances, constitute a prohibited racial discrimination pursuant to the Convention on the Elimination of All Forms of Racial Discrimination. The purpose of this article is to unpack the modus co-vivendi that seemed to prevail between the ICJ and specialised courts and tribunals until Qatar v. UAE. Building on the social ecology theory, the article frames the emergence of the ICJ's deferential attitude towards specialised courts and tribunals as a response of the Court to its shifting environment, namely a world of increasingly numerous international adjudicatory bodies competing for various resources. It then investigates the issue of whether the modus co-vivendi will survive the Qatar v. UAE judgment and offers some reflections about its practicability and normative desirability. The article makes an original contribution to the literature on international judicial behaviour as well as on competing claims to authority in the international legal order.
