"Cast-iron guarantee"

On 26 September 2007, David Cameron penned an article for the tabloid Sun newspaper, in which he provided a "cast-iron guarantee": If ever he became prime minister, he promised, "a Conservative government will hold a referendum on any EU treaty that emerges from [the Lisbon] negotiations."

Yesterday, however, Cameron U-turned and abandoned his pledge, saying he could "no more hold a referendum on the treaty than ... a referendum on the sun rising in the morning."

"The Lisbon treaty has now been ratified by every one of the 27 member states of the European Union, and our campaign for a referendum is therefore over.  Why?" he asked. "Because it is no longer a treaty: it is being incorporated into the law of the European Union."

But is this really true?  If elected, is Cameron really prevented from holding a referendum?  Couldn't he just refuse to implement the EU treaty?

Legal position

Assuming the Tories win a majority of seats at next year's general election, they could withdraw from the EU or refuse to implement the Lisbon treaty.  Under the doctrine of parliamentary sovereignty, Parliament has absolute power to change or repeal prior legislation - as the saying goes, 'no parliament can bind the hands of its successors.'  Consequently, Cameron's U-turn is not motivated by legal prudence; it's a political decision.

Political reasoning