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

There is no formal hierarchy between, or international rule of precedent applicable to, the three regional human rights systems and the eight UN Human Rights Treaty Bodies with active competence to entertain individual complaints. By scrutinising the practice of duplicative proceedings of UN Treaty Bodies (UNTBs), this article makes the argument that the res judicata and lis pendens principles have not prevented the UNTBs from reviewing cases previously examined by a regional human rights court. In doing so, the case is made that while the UNTBs usually defer to regional courts’ factual and legal findings when analyzing cases with the same parties, substantive rights, facts and events, judgments that apply the margin of appreciation doctrine are much more at risk of being revised and contradicted by UN Human Rights Treaty Bodies. Distinct opportunities for horizontal dialogue between UNTBs and regional human rights courts are thus opened.