Plaintiff S164-2018a; Plaintiff S164-2018b; Plaintiff S164-2018c, In the matter of an application for leave to issue or file

These three applications before the High Court of Australia concerned an applicant seeking leave to issue or file applications for constitutional writs. The applicant had previously applied for orders that the Minister for Home Affairs show cause why writs of prohibition and habeas corpus should not issue, seeking release from immigration detention on the grounds of the constitutional invalidity of certain provisions of the *Migration Act 1958* (Cth). These initial applications were dismissed by Gageler J, and subsequent applications for leave to appeal these decisions were also dismissed by Nettle and Gordon JJ. The current applications sought to challenge these dismissals by way of constitutional writs, alleging jurisdictional error.

The primary legal issue before the Court was whether constitutional writs, such as certiorari and mandamus, could be used to challenge decisions made by Justices of the High Court exercising the Court's jurisdiction. The applicant contended that the Justices had fallen into jurisdictional error and sought to quash their decisions and compel a hearing by a differently constituted bench. The Court was also required to determine the competence of these applications for constitutional writs in the context of High Court proceedings.

The Court reasoned that constitutional writs are directed at inferior tribunals, courts, and public officials exercising administrative jurisdiction, not at superior courts like the High Court or its Justices when exercising the Court's jurisdiction. The High Court is a superior court with the inherent power to determine its own jurisdiction, and its decisions are not amenable to supervision by constitutional writs. Challenges to errors of law in decisions of High Court Justices are to be pursued by way of appeal, subject to the grant of leave, not by constitutional writs. Consequently, the applications were deemed incompetent.

The Court ordered that the applications for leave to issue or file be refused in each of the three matters.