This is how politicians could block Brexit, according to a constitutional expert

David CameronSky NewsPrime Minister David Cameron, resigning on Friday after the EU referendum vote.

The House of Commons and the House Lords could block Britain leaving the European Union because there is no mandate on how it should be done, a constitutional expert has told Business Insider. 

“The detail of a Brexit is totally unclear,” Dr Peter Catterall of Westminster University said in a Facebook Live interview with Lianna Brinded at Business Insider.

“We know that the civil service has done absolutely no planning for a Brexit and are not in a position to advise the present government or the incoming government on how this could be done.”

The main problem, Dr Catterall says, is that the binary nature of the referendum only stated that a Brexit should happen, but not exactly how it should happen:

“On the one hand, the legislation which set up the referendum did not specify what value we have to place on it or a roadmap of what happens thereafter. All it did was offer a binary choice: leave or remain. The reason it did that was because you couldn’t have specified the detail of all that a ‘leave’ vote would require. So it couldn’t be binding. But MPs on both sides of the Commons say they regard this vote as a mandate.”

The problem with that, Dr Catterall says, is that the method of leaving the EU was not on the ballot paper:

“Now we will get a change of government in the autumn to something people didn’t vote for. It looks like we’re going to get a more hardline Tory government, and if that had been on the ballot paper it probably wouldn’t have succeeded.”

So what does this mean? Quite simply, that in a parliamentary constitution, elected MPs have every right to ignore the outcome of a referendum. 

“It is perfectly legitimate for MPs in parliament on the Remain side to say that they don’t reject leaving the EU but we reject the terms on which you are trying to do it,” says Dr Catterall.

Some MPs, including Tottenham’s David Lammy, have already called for the government to ignore the referendum, tweeting “Wake up. We do not have to do this. We can stop this madness and bring this nightmare to an end through a vote in parliament. Our sovereign parliament needs to now vote on whether we should exit the EU.”

The House of Lords will be a problem

But assuming the Commons does somehow agree on a method of Brexit, the House of Lords — the upper house of the UK Parliament that can veto laws from the Commons — will also be a major hurdle. This is because it may see the Commons as having no mandate for a method of Brexit without a General Election,” says Dr Catterall: 

“You can get [a Brexit] thought the House of Commons. The House of Lords, however, where the Tories do not have a majority — nor do the Brexit side — could certainly block it on the grounds of there being no mandate for it. You could then have a parliamentary standoff, an implication of the Parliament Act.”

“The Commons might try and ram it through over two sessions just by overruling the House of Lords” he added. “But given the difficulties of not having a mandate to do it, and you’re only doing this because you claim to have a mandate, it gets into very murky politics. How can you do something you don’t have a mandate for when you’re only doing it because you claim you have a mandate. And in the case of Boris it looks like he doesn’t actually want to do it anyway.”

And Scotland may not play ball

And what about Scotland, where residents voted overwhelmingly to Remain (62% versus 38% for Leave) and Nicola Sturgeon hinted at another independence referendum? 

“She cannot block Brexit, but what she’s doing is [more clever]. She’s the only politician who sounds like she has a plan. She’s sending out a signal to the Scottish people, to Westminster and Brussels. Risk is that the EU, particularly the Spanish, will not like to see Scotland succeed because it might send a message to the Catalonians,” says Dr Catterall.

“The British constitution doesn’t have written rules set in stone about what actually happens in this situation. Sturgeon has no constitutional right to block a Brexit as the Scottish parliament doesn’t have that power. But customarily, Scotland is involved with things that will affect them. And this affects them big time.”

NOW WATCH: Hugh Hefner’s son reacts to the sale of the Playboy Mansion

NOW WATCH: Money & Markets videos

Business Insider Emails & Alerts

Site highlights each day to your inbox.

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.