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The PM must be aware that in the battle with the EU and MPs over Brexit the UK’s sovereign status in international law is at stake.

Immediate: Friday 20th September 2019
PDF: Leave as You Entered: Brexit in International Law

As the Prime Minister prepares to leave the EU, he should be guided in executing the democratic will by the constitutional arrangements of international law.  Dr Thomas Grant* explains in Leave as you Entered: Brexit in International Law, the government should recognise that in exiting the EU no special arrangements are needed nor any ‘deal’ and that the overarching principle which should guide future talks is that the UK’s sovereign status and constitutional freedom on the international plane must be respected.

Dr Grant, an international lawyer attached to the Lauterpracht Centre in Cambridge, explains that the UK has already agreed a deal – Article 50 is itself a withdrawal agreement. Under it both parties agree terms by which to implement a member state’s international law right to leave. He warns that the new government must avoid the mistakes made by its predecessor of treating the EU as a state rather than an international treaty organisation under international law.

Any future talks with the EU must not compromise UK sovereignty by any behaviour which implies the UK is a constituent territory of the EU or under its constitution.

In a checklist of ‘next steps’ for the Prime Minister, Dr Grant proposes how best the government can make sure that UK sovereignty is not bartered away. He proposes:

  • No substitute or alternative terms for exit should be agreed other than those already in the text of Article 50 TEU.
  • New rules and arrangements can bring uncertainty in law, so nothing should be agreed without utmost scrutiny to avoid such risks.  A working group of relevant ministries, departments, agencies, and other public bodies should carry out this scrutiny under clearly set out terms and directions.
  • What matters is that the substance of the UK’s future relationship with the European Union is consistent with the implementation of the UK’s right of exit under international law.
  • The UK should have no preconceived notions about the precise format or title for any deal on its future relationship with the EU – whether a treaty, a standstill, an interim agreement, ‘mini-deals’.
  • Because future UK-EU relations will be under international law, not EU law, no EU organ—e.g. the Council, the Commission, the ECJ—should have the right to exercise jurisdiction over the UK or adopt binding decisions that determine the UK’s rights or obligations.
  • The UK can only accept future dispute settlement machinery that is fair, neutral and independent.
  • This is the common international practice. It should be taken as a given in negotiations with the EU because a state functioning in international law as the UK is in exiting the EU and will be doing in its future relations with the EU, is independent. So it cannot be presumed to be subject to such compulsory procedures by a partial body.

The proposals, prepared in August, should guide the Prime Minister to avoid being side-tracked from leaving the EU, either by MPs who seek to obstruct the democratic decision being executed, or by pressure from the EU to limit the UK’s sovereign freedom.

Welcoming these proposals, Politeia’s Director, Sheila Lawlor, says:

‘Restoring and preserving the UK’s constitutional sovereignty is fundamental to Brexit. Leave as You Entered: Brexit in International Law shows that those MPs who seek to delay or obstruct the democratic decision being executed are not merely undermining the UK’s position in the Brexit talks, but likely to undermine its constitutional sovereignty as a state in international law. Dr Grant’s timely proposals should help the Prime Minister to avoid the trap into which his predecessor and anti-Brexit MPs have fallen – of compromising the UK’s freedom and potentially its sovereignty, by strengthening the EU’s hands.’

* * * *

Leave as You Entered: Brexit in International Law by Thomas D. Grant will be released by Politeia, 14a  Eccleston Street, SW1 W9LT, on 20th September, priced £8-00. Hard copies are available from

*The Author: Dr Thomas Grant is an international lawyer and Fellow of the Lauterpracht Centre for International Law in Cambridge and Senior Research Fellow at Wolfson College. Dr Grant’s books include Aggression against Ukraine: Territory, Responsibility, and International Law (2015) and Admission to the United Nations: Charter Article 4 and the Rise of Universal Organization (2009). For Politeia, he is co-author of Avoiding the Trap – How to Move on from the Withdrawal Agreement (2019).

Enquiries to Politeia: Joshua Murphy, 0207 799 5034,