There was nothing in the EU Referendum Act that made the result legally binding
The European Union Referendum Act 2015 – the law that allowed the referendum to take place – didn’t specify what would happen in the event of a vote to leave.
We know that because it didn’t contain any explicit statement to make clear that the result would be legally binding.
The
House of Lords Constitution Committee explained in a 2010 report why that’s the case. It said “because of the sovereignty of Parliament, referendums cannot be legally binding in the UK, and are therefore advisory”.
In other words, unless Parliament actively agrees to bind itself to the result of a future referendum, it is not legally obliged to enact the outcome.
In fact, the government recognised the need to make these things explicit in 2011, when Parliament passed the legislation to allow for a referendum on electoral reform. Section 8 of the Parliamentary Voting System and Constituencies Act 2011
makes very clear that the government would have to enact a new voting system in the event of a “yes” vote.
There was no such provision in the EU Referendum Act, which in legal terms means that the result was not binding.
Indeed, this was the basis of the supreme court ruling in January 2017, which clarified that an act of Parliament was required before the government could trigger Article 50.
The culture secretary said the EU referendum was binding – it wasn’t