UNITED KINGDOM MAY NOT LEAVE THE EUROPEAN UNION -- CNN

The UK made a historic decision to leave the European Union on Thursday -- but has so far hesitated on pulling the trigger to go.

Now questions are being asked as to whether it has to happen. Here are the scenarios,

Can the referendum be ignored?

The referendum itself was advisory, rather than legally binding, and nothing was legally set in motion as a result of the vote.

Theoretically, the government could ignore the result, although doing so would presumably prompt an angry reaction from the 52% of Brits who voted to leave.

"The referendum doesn't itself trigger Brexit," said Kenneth Armstrong, professor of European law at the University of Cambridge. "It still requires the decision of a government."

Specifically, a Brexit requires the UK government to invoke Article 50 of the Treaty of Lisbon, the EU legislation governing a potential breakup.

During the referendum campaign, Prime Minister David Cameron, who led the Remain campaign, repeatedly said that a Leave victory would automatically result in the triggering of Article 50. But in the wake of the shocking Leave victory, he has said he plans to resign in October and will leave it to his successor to invoke the article -- raising hopes among some that it might not happen.

Armstrong said that while the chances of Article 50 not being triggered as a result of the referendum were "very slim," the decision ultimately remains a political one.

"With the internal politics of the both the main political parties in such turmoil, it's so hard to know what the position of the UK government is going to be," he said.

Armstrong said the vote was "an instruction from the British people to withdraw from the European Union" and as such, "cannot be ignored."

However, the longer the decision to invoke Article 50 is delayed, the more opportunity there is for politics to intervene, he said.

Though, on his part, Cameron told the House of Commons on Monday that the referendum result "must be accepted and the process of implementing the decision in the best possible way must now begin.

Will there be a second referendum?

Many disappointed Remain voters have focused their hopes on calls for another vote, with more than 3.5 million people having signed an online petition calling for a do-over, and a Labour Party MP public calling for a second referendum to be held.

There is no legal obstacle to a second referendum being held, analysts say.

However holding a second, divisive referendum simply because some people were not happy with the outcome is unlikely to prove a palatable solution, said Armstrong.

"I don't believe that this petition for a second referendum in and of itself can halt Brexit," he said.

There's one scenario under which the issue could be revisited at the ballot box: A general election could serve as a proxy second referendum on the issue.

"It would need to be a general election in 3-4 months' time that indicated a changed politics, and maybe then you'd be right to go back and check with the people that this is what we really wanted," said Armstrong.