Why would Brits need a “European court” to tell them that? Is Britain already so tired of being a nation that they are looking to authority outside themselves for justification?
They didn’t ‘need it’. The question was not put to the ECJ by the UK Government. It was put by the devolved Scottish government, which has consistently opposed Brexit since the referendum. The position was unclear, since there are no precedents and the question isn’t directly addressed in the treaties. It was the view of the EU Commission that although it would be possible for a member state to withdraw Article 50 once submitted, it could only do so with the consent of all the other member states. The ECJ rejected that, and confirmed -as the Scottish government hoped - that Article 50 could be withdrawn unilaterally.