The Supreme Court’s prorogation judgement is the latest episode in a larger parliamentary and judicial effort to dampen the strength of the executive in constitution. This is not to deny the constitutional significance (or novelty) of the judgement, but it does raise questions about how much discretion should be left to the executive in any new equilibrium.

Calls to curtail executive dominance have been heard for decades in the United Kingdom, but the 2003 Iraq War galvanized reformers. In the years since the war, the British constitution has underdone notable constitutional change aiming to rebalance the relationship between the executive and the legislature in Parliament’s favour. As the title of a 2003-2004 Commons Public Administration Committee report revealed, there has been a movement to ‘tame the Crown’. Facilitated by an increase in backbench rebelliousness and a coalition government, significant reforms were achieved within a decade. Most importantly, the Queen’s power to dissolve Parliament on the advice of the Prime Minister was transferred to the House of Commons.

The Supreme Court also contributed to this “taming”. In Evans, the Supreme Court ruled against the Attorney General’s decision to protect Prince Charles’ ‘spider memos’ from disclosure. Critics of the judgment noted that the Court arrived at this outcome through a rather creative interpretation of statute. In Miller (No 1), the Court denied that prerogative power could be used to trigger article 50 of the Lisbon Treaty and that an Act of Parliament was required to do so. While some applauded the decision as a vindication of the rights of Parliament, others observed that the Court’s treatment of the prerogative was surprising.

The Brexit saga has seen a redoubling of efforts to subject the executive to parliamentary control, including by displacing the Government’s control of the parliamentary agenda and enacting legislation to force the Government to apply for an extension.  While the Government seems in reality to lack the confidence of the Commons, confidence has not formally been withdrawn; the Government has been compelled to apply for an extension and the path to an early election has been blocked. Whatever else this may be, it is not a dominant executive.

It is perhaps not surprising then that defenders of the previous constitutional order have mused about how the Crown’s remaining prerogatives might be used to push back against Parliament. In the end, the Queen was advised to prorogue Parliament for an extended period of time, but not for a period that would span exit day itself.  In this symposium, Nick Barber has described this move as a form of constitutional hardball. To use Alison Young’s terminology, we might also see the prorogation as a kind of constitutional counter-counterbalancing. Either way, the executive deployed one of its remaining prerogative authorities to counter parliamentary opposition to Brexit.

In the past, advice to prorogue Parliament would likely have been deemed non-justiciable, as the Divisional Court found. The Supreme Court’s ruling, however, broke new ground, imposing legal controls on one of the executive’s remaining powers in relation to Parliament.  As Stephen Tierney has argued as part of this symposium, the Court deployed a novel understanding of the judiciary’s role in determining the scope and extent of a prerogative to rule that the prorogation was unlawful. It also transformed conventions about the executive’s accountability to Parliament into a constitutional principle open to judicial enforcement.

Although the judges held that the ruling was a ‘one off’, it is certainly plausible that other exercises of prerogative authority could be subject to these wider standards of judicial review. In theory, many decisions that might have been considered political questions or matters of ‘high policy’ are now open to judicial override.

Where does this leave the executive? Certainly, the prorogation has reinforced the sense in many quarters that the royal prerogative is open to abuse and that efforts to ‘tame the Crown’ should continue. Prorogation’s days as a prerogative exercised on the advice of ministers may be numbered. Yet the past decade and a half of reform, the troubles of the Johnson government, and this latest judgment suggests that efforts to constrain the executive have essentially succeeded. Perhaps the issue now is what discretionary powers and prerogatives the executive should be preserved, not how many more must be curtailed.

Once Brexit is settled, it may be worth asking what kind of powers and discretion should properly belong with the executive in the British constitution. As the Supreme Court itself emphasized, the British constitution operates with a separation of powers and according to the principle of responsible government. This leads one to ponder: what powers and responsibilities should remain with the executive as a separate, if submissive, organ of the state?

Philippe Lagassé is associate professor and Barton Chair at Carleton University, Ottawa, Canada.