Does the Prime Minister require the consent of Parliament to implement Brexit?

Question

Does the Prime Minister require the consent of Parliament to implement Brexit?

Answer

There is a case before the High Court debating whether it would be legal for Theresa May to trigger Article 50 of the Lisbon Treaty, thereby triggering the two-year negotiation period which would end with Britain’s exit from the EU, without the consent of Parliament. Is a Parliamentary vote required for her to take this action?
The power to engage in international relations and enter into (or leave) treaties with other sovereign nations is what is known as a ‘royal prerogative’ , namely a power that can be exercised by the government without the need to obtain any kind of approval from Parliament. As such, the starting position is that the government is free to trigger Article 50 without Parliament’s consent: though other actions implementing Brexit, such as repealing the European Communities Act 1972, will require consent.
Nevertheless, the government will still have to behave in a procedurally fair manner when triggering Article 50, meaning there will be a degree to which they must be open with their reasoning, consult those who might be particularly affected, and so on. It might be the case that procedural fairness in this instance requires the triggering of Article 50 to be subject to at least some form of Parliamentary debate. This is unlikely however: issues of foreign policy falling within the prerogative are usually deemed to either be non-justiciable (not capable of evaluation by the court) or requiring quite low levels of procedural fairness.

References

Table of Cases

Lloyd v MacMahon [1987] AC 625

Council of Civil Service Unions v Minister for the Civil Service [1983] UKHL 6

Books

Oliver D, Constitutional Law and Human Rights, (Butterworths, 1997)

Websites

Gavin Stamp, ‘Brexit in the High Court’ (BBC, 20 October 2016), accessed 22 October 2016