Constitutional Limits on Extra-Judicial Activity by State Judges: Wainohu and Conundrums of Incompatibility

The Kable principle is transforming Australian constitutional law. This article examines one aspect of this transformation: the emerging separation of powers limitations on extra-judicial activity by state judges. Wainohu v New South Wales, decided by the High Court of Australia in 2011, established that ch III of the Australian Constitution constrains the legislative and executive functions that a state judge can validly undertake, in addition to their ordinary judicial role, even when those functions are conferred on the judge in their personal capacity. This article discusses the impact of this decision on the ability of state judges to undertake three kinds of extra-judicial service as members of non-judicial tribunals, as Royal Commissioners, and as executive officials. In doing so, consideration is given to the relationship between Wainohu and the principles, also derived from ch III, that limit engagement in extra-judicial work by federal judges. It is claimed that Wainohu is a legitimate extension of the Kable principle that highlights the profound shift that has occurred in recent decades in the constitutional status of Australian courts and judges. Accepting this is so, an argument is advanced in favour of a conceptually unified approach to the crucial test of incompatibility with federal judicial power that is a common feature of state and federal doctrine in this area.