In Miller (No 2), the Supreme Court held that article 9 is intended to protect freedom of speech and debate in the Houses and their committees and the right of the Houses to manage their own affairs without external interference.  While prorogation may take place within the House of Lords, the Court noted that it is not a decision of the House or something upon which Members can speak or vote. It considered that the Commissioners were not acting in their parliamentary capacity, but instead were acting in an executive capacity ‘carrying out the Queen’s bidding’. Prorogation, the Court held, does not form part of the core business of Parliament, but rather terminates that business.

What other actions might be affected by the UK Supreme Court’s reasoning?  Dissolution (outside the UK in places where it remains a prerogative power) would also be an executive act imposed on Parliament from outside and not protected by art. 9 from being questioned or impeached.  But a dissolution, whether for political advantage or not, supports rather than frustrates the constitutional principles of representative and responsible government, because it gives the people the opportunity to determine the composition of Parliament and thus the Government.  It is the effect of the dissolution, not the purpose, that matters.

An exception might arise when immediately after an election has been held, the incumbent Prime Minister fails to win a majority and seeks another election rather than letting an alternative government be formed.  In such a case, the request for a dissolution might legitimately be rejected (see the example of Tasmania in 1989 where the Governor indicated he would reject such advice if given) unless no government could be formed.  Post Miller (No 2), it might also be challenged in a court as unlawful because its effect is to frustrate representative government by failing to give effect to the initial election.

The more difficult question concerns royal assent to bills.  What if a bill were passed by both Houses against the Government’s will and ministers advised the Queen to refuse assent?  Would that advice be ‘unlawful’ because it frustrated the ability of Parliament to fulfil its legislative functions?

On the above reasoning, royal assent, although announced in the Houses, is not itself a parliamentary proceeding protected by art. 9.  It may nonetheless be argued that the Queen gives royal assent as a constituent part of Parliament, acting on the advice of the two Houses, rather than ministers. While ministers may legitimately advise the Queen to defer assent or not to assent to a bill when some error in it, unknown at the time of its passage, is later identified, this is because they may be assumed to represent a majority of the House of Commons.  But if ministers have lost that majority support with respect to a particular bill, and have been defeated in both Houses in relation to its passage, there is a good argument that the Queen should not act upon advice to refuse assent to it.  On the basis of Miller (No 2), it might now be argued that such advice would be unlawful and therefore ineffective.

In the past, it was the ‘veiled sceptre’ of regal or vice-regal reserve power to reject government advice that deterred governments from constitutionally inappropriate behaviour.  As that power is gradually withdrawn from the Queen in the United Kingdom (eg by the Fixed-term Parliaments Act 2011), it seems that the courts are filling the vacuum in providing the source of deterrent.  But as long as the deterrent is effective and governments behave in accordance with constitutional principle, there should be no need for the Queen or the courts to act.

Anne Twomey is a Professor of Constitutional Law at the University of Sydney