In a boost for those campaigning for Britain to remain in the EU or hold a second referendum, a top EU legal adviser has confirmed that Britain could withdraw its notice to leave the EU unilaterally, without getting the support of other member nations.

In an opinion statement to judges at the European Court of Justice, published on Tuesday, Advocate General Campos Sanchez-Bordona pointed to a “third way” that was now open to the U.K., which is facing the real prospect of a no-deal Brexit amid massive parliamentary opposition to the withdrawal agreement reached between the British government and the EU-27 group of nations in November.

This third way involved Britain “remaining in the EU in the face of an unsatisfactory Brexit,” he wrote in the opinion. While it is a non-binding ruling, the opinion of Advocate Generals are mostly followed by judges at the ECJ. The opinion comes ahead of a ruling in a case brought by petitioners — led by Scottish Members of the European Parliament — who had sought a ruling on Britain’s ability to extract itself from the Article 50 process, by which Britain triggered Brexit over 18 months ago.

“The opinion “puts the decision about our future back in the hands of our own elected representatives where it belongs,” said Jo Maugham QC, one of the petitioners and a prominent anti-Brexit campaigner.

Future relationship

The development adds to the uncertain political landscape in the U.K., even as EU leaders and the U.K. agreed to the terms of Britain’s withdrawal, as well as a vision for the future relationship. Despite repeated direct interventions from the PM, all opposition parties, including the government’s former ally, Northern Ireland’s Democratic Unionist Party, are set to oppose the deal.

In another show of unity, the DUP, Labour, the Liberal Democrats, the Green Party, Plaid Cymru, and the Scottish National Party all signed a motion demanding the government publish the full and final advice provided to it by the Attorney General on the withdrawal deal. On Monday, the government published a summary of the legal advice, despite a parliamentary vote that had required the full advice to be released.

Opposition parties are pushing for the launch of contempt proceedings against senior government ministers over the issue, which the government has shown no signs of backing down on.

The government has insisted that its approach was in the “national interest”, that legal advice had to be treated as confidential and that publishing the advice in full would mark a dangerous precedent.

However, opposition leaders and even some Conservative MPs have criticised the decision to ignore a parliamentary vote, pointing to Cabinet sources who have anonymously briefed some of Britain’s national dailies (including the Times) that the negative conclusions of the legal advice were the real reason that the government was avoiding releasing full details.

During a lengthy debate on Tuesday, Labour’s shadow Brexit Secretary Keir Starmer told MPs that through its action the government had treated Parliament in a “contemptuous” manner.

With Britain set to leave the EU on March 29, Brexit remains mired in uncertainty. A government defeat on December 11, could pave the way to another general election or a second referendum on Brexit, though some also believe that with markets set to react dramatically, opponents could ultimately support a deal.

Five days of debate on the withdrawal deal — ahead of the December 11 vote — were set to commence on Tuesday afternoon, with an opening by the Prime Minister, though the start was delayed by the debate on the contempt of Parliament issue.