For the first time in the court’s history, all of its current 11 justices gathered to hear the legal challenge, brought by Gina Miller in December. But given the prime minister’s recent statement on the government’s negotiating objectives for Brexit, what is still at stake?
Will Brexit still take place?
Regardless of the Supreme Court’s decision, Brexit still means Brexit. The court is not questioning the decision of the people in the referendum. It is determining the relative powers of parliament and the government. In doing so, the court will look at what are called prerogative powers. These are powers that used to belong to monarchs and which are now mostly exercised by the government.
The scope of these powers is determined by the courts. In its original ruling on the Miller case in November, the High Court concluded that the government held no prerogative power to trigger Brexit. The government argued that this was the wrong decision, hence the appeal to the Supreme Court, which was heard in December.
If the government succeeds in its appeal, the secretary of state for exiting the European Union, David Davis, has the power to trigger Article 50. If the government loses its appeal, then the Supreme Court will confirm the decision of the High Court and issue its own declaration that there is no prerogative power to trigger Article 50.
What if there is no prerogative power?
The UK upholds the rule of law. One of the principles of the rule of law is that the government cannot act unless it has been given the legal power to do so. If the Supreme Court decides Davis does not have power from the prerogative, he will have to look elsewhere for a law giving him the power to trigger Article 50.
But the court’s decision will only determine whether there is a prerogative power. It will not conclude that an Act of Parliament is needed. This is because of the different powers of parliament and the courts: the Supreme Court can determine the content of the law, but it cannot actually instruct parliament to pass a new law.
Still, if the court decides the government has no prerogative power to trigger Article 50, another legal power is needed. As argued by Lord Pannick in the Supreme Court, and accepted by Prime Minister Theresa May in response to a question posed in parliament on January 18, only an act of parliament can provide it. In this case, if the government wishes to trigger Article 50, it would need to initiate legislation in parliament, asking it to give the minister the power to do so. This legislation may just empower the minister to act, or may place conditions on how the minister may exercise his powers.
The prime minister recently stated that the final outcome of the negotiations on Brexit would be put to a vote in both the House of Commons and the House of Lords. It may be that parliament wishes to place this promise on a legal basis. Or parliament may be satisfied that political assurances are enough.
What about Scotland, Wales and Northern Ireland?
Much was made during the appeal hearing at the Supreme Court of the Sewel convention, a version of which is found in the Scotland Act 2016. This convention recognises that the Westminster parliament will not normally legislate on a devolved matter without the consent of the Scottish parliament.
To date, convention has not been enforced by the courts. You cannot go to court and ask it to impose a legal obligation on the Westminster parliament to obtain the consent of the Scottish parliament.
It is unlikely that the Supreme Court will decide that Westminster is legally required to obtain the consent of the devolved legislatures. However, any discussion of the Sewel convention by the Supreme Court could reinforce the political pressure on the parliament in Westminster to involve the devolved nations if it must enact legislation to give the minister power to trigger Article 50. The prime minister stated in her Brexit speech that “the devolved administrations should be fully engaged” in the process of Brexit negotiations.
Why should we care?
Given the prime minister’s statement on Brexit on January 17 that MPs will be consulted on the final Brexit deal, it may seem that the decision of the Supreme Court will make very little difference. However, it will determine the relative power of parliament and the government.
Those who argue in favour of the original decision by the High Court do so by drawing on the importance of democracy and parliamentary sovereignty. If a majority of voters wanted the UK parliament to take back more control, then surely it should be for parliament to determine what conditions, if any, should be placed on the exercise of Article 50?
Those who argue against this stress the importance of the referendum. If parliament voted to let the people decide – which it did by passing the European Union Referendum Act 2015 – then is it not for the government to enforce the will of the people?
But this might set a dangerous precedent. It could pave the way for the government to withdraw from other treaties without the control of parliament. For example, could the government also use the prerogative to withdraw from the European Convention on Human Rights?
The decision of the Supreme Court will not alter the decision to leave the EU, but it does have the potential to radically change the nature of the UK constitution, determining the powers of the people, of parliament and of the government.