Today the Supreme Court ruled, by a majority of 8 to 3, that the Government cannot legally use prerogative powers to trigger Article 50.

The judgment rejected the Government’s appeal against the November 2016 High Court ruling, and stated that Ministers “require the authority of primary legislation” in order to give the Article 50 notice.

On the devolution questions raised, the Court unanimously held that UK Parliament is not legally required to seek consent from other devolved legislatures, e.g. the Scottish Parliament [para 151].

Both elements of the judgment emphasise the constitutional significance of the sovereignty of Parliament. Here we consider some of the implications for Parliament.

What does the judgment mean for Parliament’s role in Brexit?

The Secretary of State for Exiting the European Union, David Davis MP, responded by announcing that a short Bill will be introduced “within days” in order to provide the Government with the legal authority to give the Article 50 notice.

The majority judgment stressed that the form of such legislation is “entirely a matter for Parliament”. The judgment is solely concerned with the question of the legality of the Government’s proposed use of the prerogative. The Article 50 notice “can only be lawfully be carried out with the sanction of primary legislation enacted by the Queen in Parliament” [para 122]. A resolution of the House of Commons alone, without legislation, would not be sufficient [para 123].

What reasons did the majority give for rejecting the Government’s appeal?

The judgment is based on various aspects of a fundamental constitutional principle:

We cannot accept that a major change to UK constitutional arrangements can be achieved by ministers alone; it must be effected in the only way that the UK constitution recognises, namely by Parliamentary legislation [para 82].

The Government can make and withdraw from treaties, but this cannot change domestic law

The majority described the UK’s position as a ‘dualist’ state, which means that treaties and domestic law are seen as two separate systems. Treaties are governed by international law only and have no effect within domestic law. The UK Government has the general prerogative power to make or withdraw from treaties, but whenever treaty changes require a change to domestic law, the Government must always “seek the sanction of Parliament”. The judgment said that this system “exists to protect Parliament not ministers” [para 57].

Applying the principle to this case, the judgment held that the UK Government could withdraw from the EU Treaties only if Parliament “positively created” the power for ministers to do so [para 86]. This was because the EU Treaties are a source of domestic law and domestic rights that ministers cannot alter.

The European Communities Act 1972 [ECA] made EU law into domestic law

The Government had argued that the ECA was not the source of domestic legal rights. Instead the Act was a conduit for rights and obligations that were “contingent” on the Government’s exercise of the prerogative in conducting foreign affairs.

The majority judgment disagreed. The justices accepted that the ECA acts as a “conduit pipe” by which EU law was “grafted onto” UK law, and that the ECA is not the originating source of EU law. However, the Supreme Court also judged that the effect of the ECA was to constitute EU law as an “independent and overriding source of domestic law” [para 65].

Irrespective of whether Parliament repeals the ECA, triggering Article 50 would mean EU law is no longer a source of domestic law after Brexit. This amounts to a major constitutional change. For such a change to be brought about by ministerial decision alone, the judgment explained, would be inconsistent with the ordinary application of “basic concepts of constitutional law”, namely Parliamentary sovereignty [para 82]:

…the continued existence of the conduit pipe, as opposed to the contents which flow through it, can be changed only if Parliament changes the law. [para 84]

If Parliament had intended to enable ministers to use the prerogative to remove a source of domestic law, it would have had to be clearly included in the ECA so that Parliament would have “squarely confronted” the idea [para 87]. General words would not be sufficient.

The European Referendum Act 2015 did not enable ministers to trigger Article 50 without legislation

The majority pointed out that the European Referendum Act 2015, unlike for example the Parliamentary Voting System and Constituencies Act 2011 (which led to the AV Referendum), did not make provision for any legal consequences of either possible outcome.  If a referendum result necessitates changes to the law in order to be implemented, the UK constitution requires that the change be made through parliamentary legislation [para 121].

What did the Court say about devolution?

The supremacy of Parliament was also emphasised in the majority’s handling of the devolution issues.

Under the Sewel Convention the UK Parliament typically seeks the consent of the Scottish Parliament or that of the Northern Ireland or Welsh assemblies before legislating on devolved matters.

One of the questions raised before the Court was whether the convention means an Act of Parliament authorising the UK’s exit from the EU is contingent on the devolved legislatures’ consent? The Court unanimously said no.

Whilst the judgment stressed the importance and fundamental role of constitutional conventions, it highlighted their political nature. It emphasised that there is no role for the courts in ensuring their enforcement:

Judges therefore are neither the parents nor the guardians of political conventions; they are merely observers [para 146].

Parliament’s putting the Sewel Convention on a statutory footing in the Scotland Act 2016 (and in the Wales Bill 2016-2017) reflected the convention as a statement of political intent. The Court found Parliament’s intention was to entrench it as a convention – not as a legal rule. Despite the convention’s importance in the harmonious operation of the UK constitution, its operation lies outside the remit of the courts. The devolved legislatures therefore have no legal veto on an Act of Parliament authorising the Government to trigger Article 50.

Neither is Parliament constrained by the devolution legislation. The Northern Ireland Act 1998 (and the Scotland Act 1998 and the Government of Wales Act 2006) was enacted on the basis that the UK would remain in the EU and requires the NI Executive and Assembly to comply with EU law. However this falls short of a requirement that the UK remains a member of the EU.

A final point: accrued rights

Both sides agreed that “rights enjoyed by UK residents granted through EU law will be affected” by withdrawing from the EU Treaties [para 69]. However, the majority judgment also mentioned (in brackets) that “rights and liabilities already accrued” might continue after Brexit [para 70]. It gave no further details, and it’s not clear whether this is an acknowledgement of what have been termed ‘acquired rights‘.


Picture credit: British Parliament by Rennett StoweCreative Commons Attribution 2.0 Generic (CC by 2.0)