 In "Sidumo v Rustenburg Platinum Mines Ltd", O'Regan wrote separately to emphasise, in agreement with the majority judgment of Navsa AJ, her law-clinic colleague of thirty years earlier, that administrative law applies to labour law disputes.In the law of delict, O'Regan's contribution has been significant.In 2002, she wrote "Khumalo v Holomisa", one of the Court's first judgments on defamation law and arguably its only judgment applying the Bill of Rights directly to private parties.