Offred
The UK constitution is a collection of written laws (Bill of Rights), common law decisions and current society practises. It may be constitutional to criminalise homosexuality in 1969 but it would be unconstitutional to do so today as the views of the society has changed.
This is also a quirk in the UK constitutional framework that sometimes there is a legal right to do something provided that the said thing is never done, for example, the Monarch refusal to ascend parliament's bills.
Ok, UK did not have nationwide referendum until 1975, so this is a relatively new instrument in the constitutional framework. In recent years (such as in 2010 Parliament's referendum report), it is generally accepted that issues that have constitutional significance such as leaving the EU will need to be decided via a referendum.
Now, of course we agree that the legal status of the referendum is that it is not legally binding on the parliament. However, as with Peter Browning's submission during the constitution committee, he said:
"If the people vote one way, their representatives another, who should prevail, who is sovereign? This issue needs very careful consideration."
So, this question is not settled.
Having made further considerations on the issue, the hypothetical situation is pretty much as the following:
- Referendum is not legally binding on the parliament.
- However, if parliaments vote against the referendum then it will cause a constitutional crisis which will be settled via a general election
- If the GE returns the party which campaign to carry out the referendum than it will be carried out (sort of binding) and may lead to other constitutional reforms.
- There isn't really an option for the parliament to vote against the referendum and get away with it.