(CN) — Pivotal legal opinions on Great Britain’s decision to leave the European Union took center stage Tuesday, and stuck fresh blows to embattled Prime Minister Theresa May.

On Tuesday morning, an advocate general of the European Court of Justice issued a nonbinding opinion stating that Britain can unilaterally cancel its decision leave the EU.

A cross-party group of Scottish politicians sought the opinion, in part to bolster the case for calling a second referendum with the aim of nixing Brexit.

Scotland voted overwhelmingly to remain within the European Union during the Brexit referendum in 2016.

Also Tuesday, the House of Commons in London debated the British attorney general’s legal advice about what effects Brexit may have. The debate focused on whether ministers of May’s government should be held in contempt for releasing on Monday only a summary of the legal advice they received.

In a 311-293 vote Tuesday evening, the House passed a contempt motion and ordered the release of the full legal advice. That could happen by Wednesday.

The full legal advice was believed to contain strong warnings that a deal May struck with the EU could tie Northern Ireland to Europe’s rules and customs indefinitely. The fate of Northern Ireland is a major dilemma in the Brexit negotiations. To avoid re-establishing border checks between Ireland, which is within the EU, and Northern Ireland, negotiators agreed to keep Northern Ireland aligned with EU rules and customs until an arrangement can be agreed upon. The concern is that such a trade agreement may not materialize. So, under this scenario, Northern Ireland could be separated from the rest of the United Kingdom, creating other problems.

These are momentous days for Britain. The House of Commons is set to begin five days of discussions on the Brexit deal May has made with the EU. Under May’s withdrawal deal, Britain as a whole would remain closely aligned to the EU until a new trade agreement can be hammered out.

But her deal has been met with opposition from many sides and it is uncertain if it can survive a vote in Parliament, expected to take place next Tuesday. If the deal fails in Parliament, then May’s own survival as prime minister could be at risk. May has confidently stated she’s not leaving 10 Downing Street any time soon.

Many in her own Conservative Party, however, argue that Britain needs to make a clean break with the EU to free itself from cumbersome EU rules and allow it to strike trade agreements around the world. They say May’s deal keeps Britain tethered to the EU indefinitely.

Others argue that the deal leaves Britain worse off than if it remained part of the EU.

What happens in the coming days is viewed as a historic moment in Britain — and much is at stake economically and politically. Britain is to leave the EU on March 29, 2019.

The Tuesday opinion by EU Advocate General Campos Sánchez-Bordona added to the uncertainty over the fate of May’s Brexit plans.

In his opinion, Sánchez-Bordona advised the Court of Justice to allow a state to unilaterally revoke its decision to exit the EU before a withdrawal agreement is concluded.

He said that such a decision should be allowed as a “manifestation of the sovereignty” of a nation.

As with any international treaty, he said, a nation should be allowed to leave the EU and also decide on its own whether to rescind that decision.

He added that such a move should be permitted only if the decision is in keeping with “constitutional requirements” and “does not involve an abusive practice.”

A panel of judges with the European Court in Luxembourg is expected to issue a formal ruling in the coming days. In late November, the court held a rare special hearing on the matter and convened all 28 judges. The court will send its ruling to the Scottish courts.

Regardless, the importance of the court ruling may be limited because May’s government has said it does not plan to revoke its decision to leave the EU. But the opinion does bolster the arguments of those seeking to remain within the EU.

“We now have a roadmap out of the Brexit shambles,” said Alyn Smith, a Scottish National Party member of the European Parliament, in a statement. He was one of several Scottish lawmakers involved in the case.

He said the legal opinion was likely to be confirmed by the Court of Justice. He said the opinion should be read as a way to “stop the clock” on Brexit and showed that May was offering a “false choice” between her “disastrous deal or chaos.”

For different reasons, Britain and the EU objected to allowing unilateral revocations of Article 50, the clause that allows a member state to leave the EU.

Britain said the case should not have been taken up by the Court of Justice because the matter was “hypothetical and merely theoretical,” as neither the government nor Parliament intended to cancel the Brexit decision.

But Sánchez-Bordona said a ruling was necessary because “the dispute is genuine; the question is not merely academic, nor premature or superfluous.” He said a decision on whether a country can decide to revoke a withdrawal “has obvious practical importance and is essential in order to resolve the dispute.”

The advocate general noted that a ruling by the Court of Justice will clarify the options British parliamentarians have “when casting their votes” on whether to accept May’s withdrawal agreement.

The EU objected because it was concerned that allowing member states to withdraw from the bloc and then reverse course without the consent of other EU states could become a tool abused by nations unsatisfied with EU policies.

(Courthouse News reporter Cain Burdeau is based in the European Union.)