Central to the judge’s reasoning for their decision was the distinction between domestic law and international law. Domestic law affects individuals directly by creating or altering their legal rights. International law does not, as it is in the form of treaties between sovereign states, to which individuals are not party.
It is also essential to appreciate the difference between the crown in parliament and the crown prerogative powers. The crown in parliament effectively just means parliament, and the crown prerogative powers mean the powers of the executive government, i.e. the powers of government ministers.
It is a fundamental principal of British constitutional law that parliament is sovereign, meaning that, in the words of leading jurist Professor A.V. Dicey, parliament has “the right to make or unmake any law whatever; and, further, that no person or body is recognised by the law … as having a right to override or set aside the legislation of parliament”.
UK constitutional law also recognises that the crown prerogative powers include the right to conduct international relations, and to make and unmake treaties. This means that ministers may conduct these affairs without referring to parliament, though for reasons of political necessity they often do.
The final aspect of the situation that we need to appreciate is the legal framework through which the UK joined the EU. Put simply, the government negotiated treaties known as the Community Treaties, and then parliament passed legislation: the European Communities Act 1972. The legislation was necessary because, as previously explained, treaties are between sovereign states and do not effect individuals; an act of parliament was therefore needed to allow European legislation to become effective in UK domestic law and create rights for UK citizens.
We now come to the central issue. Theoretically, because article 50 is part of a treaty, the crown prerogative powers could be used to activate it. However, activating article 50 would affect UK domestic law, and only parliament has the power to do this.
The government argued that in passing the European Communities Act, parliament implicitly acknowledged that the crown prerogative powers could be used to affect domestic law, for example by invoking article 50, and thus gave the executive government the power to do this.
The judges did not accept this argument. They referred to a previous judgement of the Supreme Court that “the ECA is a constitutional statute, having such importance in our legal system that … it could only be repealed or amended by express language in a subsequent statute or by necessary implication from the provisions of such a statute”. The judges did not feel that necessary implication was present, as they considered that what was supposedly implied was so contradictory to the principals of the UK constitution that the Parliament of the day would have made it explicit had it been intended.
This post is part of the main blog article: “Brexit, the High Court and Article 50 – the latest twist“.