British Prime Minister Theresa May launches her Supreme Court challenge on Monday against a High Court ruling that she needs to seek parliamentary approval before triggering Article 50.
While Mrs May had indicated that she wanted to trigger Article 50, to begin the official negotiation process of leaving Europe, a challenge in the High Court led to three judges ruling that she needed the say-so of parliament to do so.
If the Supreme Court does agree with the High Court, then Mrs May’s timetable could be in trouble. Britain decided to leave Europe in the June referendum, but some politicians and media outlets are claiming that judges are deliberately trying to prevent the divorce from Europe.
In a case set to last four days, all 11 of the Supreme Court justices will be sitting on the panel. It is the first time that every one of the courts justices will have taken part in the same panel, and they are expected to announce their verdict in the New Year.
Supreme Court Vice President Brenda Hale said the case would throw up complex questions about the constitutional relationship which exists between the government and parliament. She said she doubted there was a written constitution anywhere in the world which would provide the answers.
If Mrs May wins her appeal, she will be able to go ahead with the timetable she promised following the referendum. However, if she loses, then parliament could do everything possible to try to block Brexit altogether. Most MPs supported staying in Europe in the June referendum.
Analysts say that the more parliament is allowed to get involved, the less chance there is that Britain will make a hard exit from Europe in which it puts immigration control over access to the European single market.
The Liberal Democrats are even threatening to vote against Article 50 entirely unless Mrs May agrees to hold a further referendum once a final deal has been threshed out.