Administrative law updater: Judicial review of prerogative powers

By John Carroll, Cain Sibley, Neil Cuthbert
18 Oct 2019
The decision in R (Miller) v The Prime Minister [2019] UKSC 41 shows courts can invalidate the exercise of prerogative powers, even in highly charged political circumstances such as Brexit.

What is the problem decision-makers face?

The exercise of prerogative (or non-statutory executive) powers is fundamental to Australia's constitutional system of government. In 1902, Alfred Deakin observed:

"shorn of prerogative powers, the Commonwealth Executive would be a mere appendage to the Parliament – a board of subordinate officers exercising such powers as might be conferred upon it, but without independent authority of any kind."

Decision-makers will occasionally need to exercise these prerogative powers to make decisions. For example, a decision-maker may grant a pardon: Ogawa v Attorney-General (No 2) [2019] FCA 1003. Prerogative powers also include the power to enter into treaties and declare war, to grant honours, and to protect the nation and preserve public safety.

The High Court has not addressed this issue for some time, but it is important to remember that exercises of prerogative powers can be challenged in judicial review proceedings. Where a judicial review challenge succeeds, a Court may declare that an exercise of prerogative power, or the recommendation leading to it, was contrary to law.

How did Miller (No 2) (UK) affect this?

The UK Supreme Court in R (Miller) v The Prime Minister [2019] UKSC 41 (Miller (No 2)) shows that judicial review of prerogative powers can occur – and be successful – in highly charged political circumstances, such as prorogation of the UK Parliament in the lead up to Brexit.

To determine the lawfulness of the exercise of the prerogative to prorogue the UK Parliament, the Supreme Court devised a two-part test:

  1. What was the effect of the decision?
  2. Was there a reasonable justification for that effect?

The Court followed the usual course of issuing a declaration, but the declaration effectively invalidated the decision.

The facts and decision in Miller (No 2) (UK)

In the weeks leading up to Brexit day (31 October), when the UK is set to leave the European Union, the British Prime Minister prorogued parliament for five weeks to allow for a Queen’s Speech. Typically, prorogations last for days, not weeks. In the UK, the power to prorogue parliament is prerogative.

The UK Supreme Court considered that the exercise of that prerogative was justiciable. Applying the two-part test, the Supreme Court unanimously held the prorogation was "unlawful, null and of no effect":

  • the effect of the prorogation was to frustrate or prevent "the constitutional role of Parliament in holding the Government to account", as Parliament would not sit for five out of a possible eight weeks before Brexit day. As the House of Commons did not "support the Prime Minister" on this issue, it was "especially important" that the Prime Minister "be ready to face the House of Commons".
  • there was no reasonable justification for the prorogation. On the evidence before the Court, it was "impossible" to conclude that there was "any reason – let alone a good reason". Had a reason been identified, given the nature of the decision, a ‘great deal of latitude’ would have been afforded.

The day following the Court’s decision, the House of Commons resumed sitting and the prorogation was expunged from the record.

After Miller (No 2), here's what you need to remember

Although this decision occurred in a different constitutional and judicial review context, the High Court of Australia is likely to consider the analysis in Miller (No 2) in any future challenge to the exercise of prerogative powers in Australia.

Unsurprisingly given the Westminster foundations of the Australian Constitution, the High Court has a history of drawing on British administrative law, most recently by adopting the materiality test for jurisdictional error. The decision in Miller (No 2) reaffirms that exercises of prerogative powers are reviewable by Courts. It also emphasises the importance of clearly articulating both the effect of a decision and the justification for it.

Decision-makers should be careful to identify any non-statutory powers that may need to be exercised in order to reach an outcome in a given case. When exercising such powers, or making a recommendation leading to their exercise, decision-makers should ensure that they:

  • articulate a clear basis for their decision or recommendation; and
  • consider the effects of the exercise of prerogative power, and provide an adequate justification for those effects.

If a challenge to the exercise of a prerogative power succeeds, decision-makers should be mindful that a Court may have power to make a declaration that effectively invalidates the decision. This might be the case even where the character of the decision appears quintessentially political.


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