The Court held that where separate judicial review proceedings challenge distinct decisions made under different legislative regimes (here, the WA Environmental Protection Act and the Commonwealth EPBC Act), it is seriously arguable that they constitute separate justiciable controversies rather than a single 'matter' for federal jurisdiction purposes, even where the two regimes interact through an accredited assessment process. The fact that a party proposed but then did not press a ground of review linking the two proceedings was insufficient to enliven federal jurisdiction — this was distinguished from cases where a federal issue was pleaded but not ultimately decided, because here the ground was never before the court at all. On discovery, the Court ordered production of all material before the decision-maker, holding that where the manner of decision-making is challenged on unreasonableness grounds, supervisory review cannot be exercised without regard to the relevant material, and the decision-maker should not be the arbiter of what is relevant.
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