However the Court rejected arguments that the UK's devolved assemblies in Northern Ireland, Scotland and Wales should give their assent before Article 50 in invoked. But the decision may potentially change the Prime Minister, Theresa May plans to trigger Article 50 before the end of March as she will now seek the consent of Parliamentarians first.
The British government launched a Supreme Court battle over who has the power to trigger the formal process of leaving the European Union, seeking to overturn a legal ruling that could derail its Brexit strategy.
The most powerful Court in the land upheld a High Court decision that ruled it unconstitutional for Theresa May to formally trigger the process of leaving the EU without first consulting MPs. The government's lawyers argued that the High Court ruling was wrong that parliament had accepted before the referendum that ministers would use ''prerogative'' powers to implement its result. But the government's lawyers accepted that Article 50(1) allows the UK to withdraw from the European Union with its own constitutional requirements.
The government argument failed to establish the relationship between the Crown's prerogative, i.e. the residue of monarchical authority that is now exercised by ministers, and the doctrine of parliamentary sovereignty. On the one hand, it is an established feature of the UK constitution since 1688 that an Act of Parliament cannot be supplanted by the exercise of prerogative power. On the central issue, settled since 1688, the Crown cannot use prerogative to remove an Act of Parliament. On the other hand, it is equally established that the prerogative powers of the Crown cover international relations and the conclusion of treaties.
The government argued that the Crown has a prerogative power to authorise the UK's withdrawal from the EU, and that this power can only be taken away by express terms in an Act of Parliament. In the absence of express statutory words, the prerogative powers of the Crown over Article 50 remain intact. This argument was correct, but only with respect to rights and obligations created as matter of international law. As soon as individual rights protected by domestic law are affected, Parliament must be involved.
In relation to individual rights protected in domestic law that could be affected by the EU withdrawal, there are three categories: 1. Rights that were capable of replication in domestic law, 2. rights enjoyed by the UK nationals in other Members states, 3. rights that cannot be replicated in UK law and would be lost upon withdrawal.
In regard of the individual rights protected in domestic law that could be affected by the EU withdrawal: rights that capable of replication in domestic law and rights enjoyed by the UK nationals in other members states, there is nothing in principle to stop Parliament from enacting its provisions in domestic law. In regard of the individual rights protected in domestic law that cannot be replicated in UK law and would be lost upon withdrawal, the government agrees that those rights would irretrievably be lost upon withdrawal. This is here lies the government's defeat.
This is why the government lost its appeal:
First, the notification of the European Council under Article 50 could be reversed, then the Parliament must be involved. And since the question involves a question of the EU Treaty law, the final answer could only be given by the Court of Justice of the EU.
Second, by agreeing that the Article 50 notification would inevitably lead to the loss of some individual rights, rights that cannot be replicated in domestic law, the government lost its appeal.
The ruling does throw a spanner in the works of the government's Brexit strategy. But its focus is strictly constitutional, not political. The Supreme Court has not expressed an opinion on whether Article 50 should be triggered. The only question it examined is whether, as matter of the UK constitutional law, the Crown acting through the government, is entitled to use prerogative powers to trigger Article 50 in order to cease to be a member of the European Union.
By Guylain Gustave Moke
International Affairs Expert
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