Anti-Brexit supporters demonstrate outside the conference centre at the annual Labour Party Conference in Liverpool, Britain, September 23, 2018. REUTERS/Phil Noble

EDINBURGH (Reuters) - The European Court of Justice has set a Nov. 27 date for a hearing to decide whether Britain’s parliament can unilaterally change its mind on Brexit, a legal source told Reuters, adding that the case is moving fast.

Scottish lawmakers opposed to Brexit filed a petition with Scotland’s Court of Session last year to show that Britain has a unilateral option of staying in the world’s biggest trading bloc, once the outcome of Brexit is known.

They argue that while there is no legal doubt that Britain could stop Brexit with the permission of the other 27 EU member states, it should seek to establish a legal right to do so unilaterally, whether the rest of the bloc likes it or not.

The news comes as Britain appears to be on the brink of an agreement with Brussels over its decision to leave the European Union, diplomatic sources said on Friday.

Because no country has ever left the EU before, the exact meaning of Article 50 of the Lisbon Treaty which regulates withdrawal from the EU is untested.

“We have our hearing on November 27 at 9am” the source said, speaking on condition of anonymity. “This shows the ECJ is moving at breakneck speed on this case.”

The ECJ, which rules on the meaning of EU law, hopes to make a decision on the case before Christmas, a source close to the case told Reuters on Thursday. No one at the ECJ was available to comment.