Mr Aird said the judgment, flowing from a High Court case in 2016, shows the complexity of the analysis required and also explains why the British government appealed the High Court decision.

“Only three of the 11 judges disagreed, reflecting the complexity of the constitutional analysis, and perhaps justifying the decision of the government to appeal,” Mr Aird said.

The government appeal argued that triggering article 50 without parliamentary consent was allowed because it fell within the executive’s prerogative power.

In essence, the government took the view that Brexit is about membership of the European Union, which it argued is a prerogative matter.

Writing for The Conversation, Birmingham Law School professor Fiona de Londras explained that prerogative powers are limited to ensure that the integrity of parliamentary sovereignty is persevered.

“[Prerogative power] also cannot usually be used to reduce the rights enjoyed by people in the UK – which withdrawal from the EU would almost certainly do. Even though triggering article 50 does not bring those changes about on its own, it puts in train a process the inevitable end of which is these fundamental constitutional and legal changes,” Professor de Londras said.

Mr Aird also highlighted the significance of the court’s position that Brexit could be legally enacted without the consent of Scotland, Wales and Northern Ireland. The decision clears the way for the British Parliament to proceed with its own exit timetable, he said.

“A decision in favour of the assemblies would likely have derailed Theresa May's proposed timetable for triggering article 50, and meant that the Brexit limbo in which we are currently living would have likely continued for some time yet,” Mr Aird said.  

“The judgment means that [the Prime Minister] has a fighting chance of keeping to that timing, provided that Parliament does not seek to make significant amendments to the authorising bill. The expectation is that the bill will be kept very short, to minimise the scope for troublesome amendments,” he added.

Another interesting aside in the judgment, Mr Aird observed, was Lord David Neuberger’s opening comment stating that the decision had nothing to do with the political question of whether the UK should exit the EU or when it should exit.

“The legal challenge concerned how it should exit,” Mr Aird said.

“The Supreme Court has issued a legal judgment and not a political or policy statement. 

“Far from being the 'enemies of the people', the power of the independent judiciary to ensure that our government acts in accordance with the law is one of the constitutional fundamentals of British democracy.”

The British government is now left to decide how to formulate the article 50 bill to ensure a smooth passage through Parliament.

Although it is unlikely that the Parliament will "perpetually refuse" the bill to be triggered, Professor de Londras said this week's decision ensures that Parliament is empowered to make the government accountable for how it gives effect to the Brexit outcome the people voted for.