Official and scholarly sources confirm a genuine causal mechanism: EU membership transferred law-making competence in certain policy areas to the EU level, and EU law had primacy over conflicting UK law in those areas. The UK Parliament itself acknowledges that membership "resulted in a loss of sovereignty in so far as the Government has been obliged to fulfil the requirements of the EU Treaties and law." The EU held exclusive competence in areas such as the customs union, common commercial policy, and conservation of marine biological resources, and shared competence in many others, including the internal market, environment, agriculture, and consumer protection. House of Commons Library research (cited by Full Fact) finds that a meaningful, though contested, proportion of UK law was influenced by the EU, with estimates ranging widely depending on methodology. However, the evidence does not support the stronger implication made in the interview turn ("it doesn't really make any difference who's in No 10"). Major domestic policy areas that most drive election outcomes—tax, public spending, health, education, welfare—remained largely outside EU competence. Research by Bartle, Dellepiane-Avellaneda, and McGann covering 1945–2015 finds that party control (which elections determine) had a significant, consistent effect on the broad direction of domestic spending policy throughout the period of EU membership: Labour governments raised spending, Conservative governments cut it. Constitutional analysis (e.g., Public Law for Everyone) also notes that parliamentary sovereignty was not extinguished by EU membership; Parliament retained the domestic legal authority to override or repeal the European Communities Act 1972, and the European Union Act 2011 expressly affirmed that EU law had effect only because Parliament allowed it. Thus, EU membership plausibly reduced the scope of policy areas that UK general elections could decisively affect, and this scope may have widened as EU competence expanded over time. But the effect was partial: elections continued to determine the broad direction of the most salient domestic policies. The causal link is credible but not as decisive as the claim implies. Sources: - UK Parliament, "UK Parliament and the EU: Contemporary context" — https://www.parliament.uk/about/living-heritage/evolutionofparliament/legislativescrutiny/parliament-and-europe/contemporary-context/ - Full Fact, "UK law: What proportion is influenced by the EU?" — https://fullfact.org/europe/uk-law-what-proportion-influenced-eu/ - House of Commons Library, "How much legislation comes from Europe?" — https://commonslibrary.parliament.uk/research-briefings/rp10-62/ - Public Law for Everyone, "If European Union law is supreme, can Parliament be sovereign?" — https://publiclawforeveryone.com/2016/02/21/1000-words-if-european-union-law-is-supreme-can-parliament-be-sovereign/ - Bartle, Dellepiane-Avellaneda & McGann, "Policy accommodation versus electoral turnover: policy representation in Britain, 1945–2015," Journal of Public Policy — https://www.cambridge.org/core/journals/journal-of-public-policy/article/policy-accommodation-versus-electoral-turnover-policy-representation-in-britain-19452015/A8577DECDEC25A302CE1DE1D26DD28D7 - UK Government, Review of the Balance of Competences: Trade and Investment — https://assets.publishing.service.gov.uk/media/5a7ba80340f0b638d61be162/bis_14_591_balance_of_competences_review_Trade_and_investment_government_response_to_the_call_for_evidence.pdf