Defer or Revise? Horizontal Dialogue Between UN Treaty Bodies and Regional Human Rights Courts in Duplicative Legal Proceedings.

The article examines the absence of a formal hierarchy or binding precedent between the three regional human rights systems—the European Court of Human Rights (ECtHR), the Inter-American Court of Human Rights (IACtHR), and the African Court on Human and Peoples' Rights (ACtHPR)—and the eight United Nations Human Rights Treaty Bodies (UNTBs) that entertain individual complaints. It focuses on how principles designed to prevent duplicative proceedings, such as res judicata and lis pendens, have not stopped UNTBs from reviewing cases previously examined by regional courts, especially when regional judgments apply the margin of appreciation doctrine. The Human Rights Committee (HRC) and Committee against Torture (CAT) illustrate divergent approaches: the HRC often conducts de novo reviews of legal questions and may revise regional court findings, particularly where regional courts afford wide discretion to states, while the CAT tends to defer more to regional decisions. The article highlights tensions between promoting universal human rights standards and respecting regional particularities, noting that some states have issued reservations limiting UNTBs' competence to re-examine cases decided by regional courts. Ultimately, the interplay between UNTBs and regional courts creates opportunities for horizontal dialogue but also raises challenges related to legal coherence, forum shopping, and the legitimacy of overlapping human rights adjudication.