The UK Constitutional Law Association’s blog has a number of interesting posts about the constitutional aspects of Britain’s withdrawal from the European Union. Particularly noteworthy is a piece by Nick Barber, Tom Hickman, and Jeff King arguing that Britain might not be able to trigger Article 50 without an Act of Parliament.
Their logic runs like this: giving notice under Article 50 is an irreversible decision. The Treaty of Lisbon does not contain any provision to rescind such notice, and countries that invoke Article 50 will be automatically released from the treaties of the European Union after two years even if an agreement with the other member states is not forthcoming (though this two-year period can be extended with the unanimous agreement of the other member states). Since invoking Article 50 is tantamount to withdrawing from the EU, the authors argue that Parliament must give permission before it happens. This is because the United Kingdom’s relationship with the European Union is governed by Acts of Parliament (e.g., the European Communities Act 1972), and withdrawing from the EU would effectively repeal those acts without parliamentary consent. Since it’s long been accepted that the Crown cannot unilaterally negate statute law, the Government cannot use the royal prerogative to activate Article 50.
It’s a very solid argument, but I’m not 100% convinced. As Adam Tucker has pointed out elsewhere on the UKCL Blog, the problem lies in section 2(2) of the European Communities Act, which states that the Executive may make provision “for the purpose of implementing any EU obligation of the United Kingdom, or enabling any such obligation to be implemented, or of enabling any rights enjoyed or to be enjoyed by the United Kingdom under or by virtue of the Treaties to be exercised” (emphasis mine).
Article 50 of the Treaty of Lisbon gives member states the right to withdraw from the EU, so it seems that the Government could simply make a statutory instrument under section 2(2) when giving notice of its intent to withdraw (given the significance of the matter, I suspect that it would be done by the Queen-in-Council). Parliament would still be involved in this process since paragraph 2(2) of Schedule 2 of the European Communities Act provides for parliamentary oversight of these statutory instruments–if they haven’t been approved in draft form by both Houses, they can be annulled by resolution of either House. If this is the case, the question of the royal prerogative would be moot. As the House of Lords observed in Attorney-General v De Keyser’s Royal Hotel Limited ( UKHL 1,  AC 508), the Crown cannot fall back on the prerogative if Parliament has created a statutory power.
Regardless of the mechanism involved, parliamentary involvement with Brexit could be incredibly messy. Passing an act could take a very long time. If pro-EU MPs decide to play hardball, the Government could be unable to limit debate. The House usually agrees to a programme motion that establishes a timetable for the bill’s legislative journey, but the Government’s majority is slim enough that such a motion could easily be defeated. If that were to occur, the bill could be filibustered by pro-EU MPs.
And then there’s the issue of the House of Lords. Given its leftward tilt, a Brexit bill could receive a chilly reception from their lordships. They could reject it outright or subject it to endless debate (there’s no such thing as a programme motion in the Lords). Ordinarily, peers would not adopt such a confrontational stance, but they’ve definitely grown more assertive in recent years. The Government could ultimately use the Parliament Acts to get the bill onto the statute book, but that would take years.
Proceeding by statutory instrument might be faster since there would only be a single up-or-down vote in each House, but it would also give the House of Lords an absolute veto over Brexit. Unlike bills, statutory instruments are not subject to the Parliament Acts.
The fact that there is so much uncertainty over Parliament’s role in Brexit does not bode well for the future. European leaders have made it clear that they want action sooner rather than later, but the Government might well find that it’s unable to oblige.