A referendum would be sufficient.
'The City' World Conquest: The making of the 'One World Earth Corporation'
We should Test the Legality of the Treaties Surrendering SovereigntyAbout a former PM and the treaty of Rome.
The reward of £35,000, paid personally to Heath, in the guise of The Charlemagne Prize, was handed over to him after he had signed the Treaty of Rome.
"Heath later confirmed that he had lied to the British people about the implications of the Treaty. He told the electorate that signing the Treaty of Rome would lead to no essential loss of National Sovereignty but later admitted that this was not true - and he knew it was not true. He said he lied because he knew that the British would not approve of him signing the Treaty if they knew the truth.
Vernon Coleman 2011
Cameron, presumably with HMQEII's permission, allegedly got £10 million for his signature surrendering the country.