Fifteen Eighty Four

Academic perspectives from Cambridge University Press


Brexit and the Foreign Affairs Prerogative

Campbell McLachlan

On Monday 5 December 2016, the UK Supreme Court will hear the Government’s appeal from the judgment of the Divisional Court in R (Miller) v Secretary of State for Exiting the European Union. It is the case of the century on the scope of the foreign affairs treaty prerogative. A unanimous Divisional Court held that the Government could not give notice of withdrawal from the European Union Treaty without the authority of Parliament. Parliament had given directly effective EU rights the force of law in the UK under the European Communities Act 1972 and these rights could not be taken away without its approval.

The Government claims in its brief to the Supreme Court that ‘acts of the Government in the exercise of the prerogative can alter domestic law.’ In my view, this central proposition in the Crown’s case is contrary to the ‘general principle that the Crown cannot change the law by the exercise of its powers under the prerogative. This was the great principle which was settled by the Civil War and the Glorious Revolution in the 17th century.’

The fact that there can in 2016 be serious controversy about so fundamental a principle shows how underexplored the foreign affairs power has been in British Constitutional law. It has been shrouded in what Gina Miller herself described as ‘the ancient secretive Royal prerogative’. Strangely for such a pivotal power, there had been no recent book dedicated to exploring the legal constraints on its contemporary exercise.

It was in order to fill this gap that I decided to write my book Foreign Relations Law. What I found in my research is that, while the Government undoubtedly retains very important powers in the foreign relations sphere–including the power to make and unmake treaties–the foreign affairs power is distributed among the three organs of constitutional government. Both Parliament and the courts have important functions of their own in this sphere as well. It is for Parliament to determine the law of the land. What Parliament has provided, the Government may not dispense with by the exercise of prerogative power: s 1 Bill of Rights Act 1688. The courts will intervene in order to protect the rights of individuals, where they are infringed by the exercise of the foreign relations power.

This is what makes Miller such an important case, as I explained in a recent radio interview. It will not only determine the future course of the United Kingdom’s exit from the European Union. It also puts in play those most basic principles of the British Constitution: Parliamentary sovereignty and the Rule of Law, since ‘[i]t is’, as Lord Diplock said, ‘350 years and a Civil War too late for the Queen’s courts to broaden the prerogative:’

About The Author

Campbell McLachlan

Campbell McLachlan QC is Professor of International Law at Victoria University of Wellington. He is a New Zealand Law Foundation International Research Fellow and sometime Visiting...

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