The UK Supreme Court’s ruling voiding Boris Johnson’s suspension of Parliament is one for the ages -- a landmark in British constitutional law of the kind that comes around only once every few centuries.

The court’s judgment tried to downplay how astonishing its decision was. But the reality is that the unanimous court broke new ground in making the judiciary, not Parliament, the ultimate arbiter of constitutional legality in the UK. Although, the court said this case was a “one-off”, it nevertheless sets a radical new precedent, thereby fundamentally altering the British constitution, which evolves by customary practice rather than amendment.

A core idea of the judgment was that suspending or “proroguing” Parliament was an executive act.

Technically, Parliament doesn’t send itself home when it’s prorogued. Rather, the prime minister advises the queen to exercise her traditional royal prerogative to instruct Parliament to take a break. The way the court presented the question it had to answer was as whether “the executive” -- effectively, the prime minister -- acted within the legal limits when he sent Parliament home for longer than usual with no apparent purpose other than to block discussion of Brexit at a moment of major political consequence.

Framed in this way, the case did not pose a conflict between parliamentary sovereignty and the authority of the judiciary. Indeed, the judgment, written by Lord Brenda Hale, the court’s chief, insisted that the court was actually upholding the power of Parliament, because it could only act in its sovereign capacity and hold Boris Johnson’s government accountable when actually in session.

From the standpoint of pure democratic theory, this approach makes some sense. The prime minister isn’t the Parliament. So if he can effectively send the Parliament home to prevent it from annoying him. That would seem to undercut the Parliament’s authority.

Yet at the same time, there’s also something very strange about this way of looking at the case. In real-world terms, Johnson is prime minister by virtue of Parliament. The Conservative Party formed a government. That party chose him to be prime minister. A parliamentary vote of no-confidence could bring down his government -- and Johnson with it. When a prime minister selected by Parliament chooses prorogue, that looks in power-political terms very much like a political decision ultimately attributable to Parliament.

Traditionally, the idea of parliamentary sovereignty was supposed to mean that Parliament had the ultimate authority to review policy decisions by the prime minister and his or her government. But now the Supreme Court has taken it upon itself to review whether a particular decision is “lawful.” That creates a tension between parliamentary sovereignty and judicial review.

The court addressed this tension by saying that judicial review is different from Parliament holding ministers responsible, because it focuses on legality, not politics. But that logic is somewhat circular. Johnson’s decision to prorogue Parliament was definitely political. And until the Supreme Court’s judgment, there was no judicial precedent to say it was unlawful.

Even more astonishing was the court’s explanation of how it determined that Johnson overstepped his power to prorogue. As the court forthrightly acknowledged, “a prerogative power is not constituted by any document.” That led the court to admit, with true British understatement, that “determining” the unwritten power’s limits “is less straightforward” than determining the extent of statutory power.

The court went then went on to determine the limits of the prorogation power by looking to the effects of a prorogation would have. A given prorogation would be unlawful if it “has the effect of frustrating or preventing without reasonable justification, the ability of Parliament to carry out its constitutional functions as a legislature and as the body responsible for the supervision of the executive.” In such a situation, the court held it “will intervene if the effect is sufficiently serious to justify such an exceptional course.”

Again, this is perfectly reasonable as a matter of democratic theory. But as a matter of British constitutional law, it’s radically new.

In essence, the court assumed for itself the power and authority to determine whether a given exercise of a traditional constitutional power would have bad effects. That makes the UK Supreme Court into the guardian of Britain’s constitutional democracy.

What’s radical about making the court the protector of democracy is that is displaces Parliament from that traditional role. Under the guise of saving Parliament and its sovereignty, the Supreme Court effectively placed itself above Parliament.

Given that this has all happened due to the Brexit vote, the greatest irony here is that Britain only has a Supreme Court because European Union rules essentially required it to establish one. To fulfill those requirements, it changed the name and institutional function of its highest judicial body, the old “law lords,” making it independent of Parliament. That’s why the UK Supreme Court is just 10 years old, while Parliament can trace itself back to the Middle Ages.

When the old law lords, technically a committee of the House of Lords, became the UK Supreme Court, defenders of the transformation said it was only a formality. Yet the exercise of judicial review in the prorogation case strongly undermines that decadeold argument. Call a group of judges a Supreme Court, and it will start acting like one.

The British Constitution changes step by step. The steps, however, come in different sizes. This one is more like a leap -- a leap into the world of judicial supremacy. Constitutional lawyers be talking about it 100 years from now, and beyond.


Noah Feldman
Noah Feldman is a Bloomberg Opinion columnist. He is a professor of law at Harvard University and was a clerk to US Supreme Court Justice David Souter. His books include “The Three Lives of James Madison: Genius, Partisan, President.” -- Ed.

(Bloomberg)