The government’s appeal was dismissed in the Supreme Court yesterday. This means that Parliament has to give its approval before the formal process of leaving the EU can begin. The judgement and summary documents are available here.
The original case was about prerogative powers, defined by the High Court in the original case as “the residue of legal authority left in the hands of the Crown” however as the UK has a sovereign parliament it is argued that prerogative powers cannot be used to overrule legislation. The government argued, however, that it did have the prerogative power to “make and unmake treaties” allowing it to launch the process without requiring an Act of Parliament.
The Scottish Government was also involved in this case. The Lord Advocate’s intervention proposed that triggering article 50 required an Act of the UK Parliament and as a result also required a Legislative Consent Motion of the Scottish Parliament, under the Sewel Convention, given the effect it would have on matters devolved to the Scottish Parliament. However, in regards to the Sewel Convention the Supreme Court has ruled that the policing of its scope and the manner of its operation does not lie within the constitutional remit of the judiciary. This means the Scottish Parliament, as with the other devolved administrations, cannot veto the triggering of Article 50.