The High Court's decision in Kirk v Industrial Court of New South Wales (2010) 239 CLR 531 follows the 2009 decision in International Finance Trust Co Ltd v New South Wales Crime Commission (2009) 240 CLR 319; both decisions breathing new life into the principle from Kable v Director of Public Prosecutions (NSW) (1996) 189 CLR 51. Whereas the 2009 case involved a relatively straightforward application of Kable (as developed and re-articulated in subsequent cases), the decision in Kirk is far-reaching. The High Court has effectively extended the reach of ch III of the Constitution, holding that the supervisory jurisdiction of the state supreme courts is a defining characteristic of those courts and cannot therefore be removed. The implications of the decision will be played out over time, in cases where jurisdictional error is alleged and where state privative clauses come under closer scrutiny by the courts. However, the wider significance of Kirk lies in the High Court's defiant stance with respect to preserving its own supervisory role in reviewing the fundamental errors of inferior courts and tribunals. In this respect, the impact of Kirk may not be completely felt until the matters which the Court was ultimately able to sidestep in Kirk, but which absorbed the parties and interveners in their submissions, arise for determination in a future case.