R v Isaac; ex parte Transport Workers Union

The High Court of Australia considered an application for prohibition brought by the Transport Workers Union (TWU) against Mr. Isaac, the Registrar of the Industrial Registrar's Office. The dispute concerned the validity of certain rules of the TWU, which the Registrar had refused to register on the grounds that they were contrary to the public interest. The TWU sought to challenge this refusal.

The central legal issue before the High Court was whether the Registrar had acted within his statutory powers in refusing to register the TWU's rules. Specifically, the Court had to determine the scope of the Registrar's discretion under the relevant legislation to refuse registration on the basis that the rules were contrary to the public interest, and whether his decision in this instance was a proper exercise of that discretion.

The Court reasoned that the Registrar's power to refuse registration on public interest grounds was not unfettered. It required a substantial and demonstrable reason connected to the public interest, not merely a subjective disinclination. The majority found that the Registrar had failed to establish a sufficient basis for his refusal, concluding that his decision was based on an erroneous interpretation of the public interest and was therefore invalid. The Court applied principles of administrative law concerning the proper exercise of statutory discretion.