Today's legal opinion that the UK has the unilateral right to withdraw its notice of withdrawal from the EU is 'unwarranted interference with parliamentary proceedings', according to an expert in parliamentary privilege. Giving an opinion in Wightman and Others v Secretary of State for Exiting the European Uniona case referred by the Court of Session in Scotland, European Court of Justice advocate general Campos Sánchez-Bordona rejects the UK government's claim that the case is inadmissible as it is purely hypothetical. 

Opinions by the advocate general are not binding on the court but are a very strong indication of which way the decision, expected in the next few days, will fall. 

The advocate general proposes that the Court of Justice should, in its judgment, declare that Article 50 of the Treaty of European Union allows the unilateral revocation of the notification of the intention to withdraw from the EU, provided that the revocation has been decided upon in accordance with the member state’s constitutional requirements, is formally notified to the European Council and does not involve an abusive practice. 

The opinion was welcomed by Liberal Democrat Tom Brake and Labour's Chris Leslie. In a statement issued by London firm Bindmans, they said: 'The court usually follows the advocate general and we hope that it will do so in this important case. For political reasons, HMG has tried very hard to stop the court giving a ruling on the important topic of revocability. We await the court's judgment with considerable interest, giving the timing of the current parliamentary processes on Brexit.'

However in a paper for thinktank Policy Exchange, Sir Steven Laws, first parliamentary counsel from 2006 to 2012, argues that it is not the function of courts to give unsolicited legal advice to parliament. 'It is certainly not the function of the courts to inform the debate on issues that might form the basis of a motion of no confidence in the government. The courts should not seek to pre-empt or prescribe decisions on the relevance of particular matters to proceedings in parliament. In the House of Commons that is the exclusive prerogative of the speaker.'