The short answer to the question is that Article 50 of the Treaty of Lisbon allowed a state to leave. Such an answer raises the question of why the United Kingdom has, so far, been the only state to invoke and execute the right to leave under the article. The reasons why some of the poorest and most deprived areas of the United Kingdom led it out of the EU on June 23, 2016, are complicated and do not fit into an easy chronological or legal order. From the very broadest point of view, membership of the Union, and the Community before it, was a limitation on the freedom of the House of Commons to legislate and represented a second sovereignty in the UK. It is very tempting to take a ‘grand sweep of history’ approach and to note that the Westminster regime has never dealt well with alternative sovereignties. The claims of the Catholic church were expunged in 1533, for instance, as were those of Wales to separate treatment; the Irish parliament was subordinated to Poyning’s law, ...
This is a collection of personal and largely unedited observations covering the years from 2006 to now; I assert my copyright but am fine with links and footnotes. Some posts are obviously much more researched than others, and any errors are wholly mine except where I have innocently disseminated or linked to other bloggers or commentators.