Just discovered that Neil MacCormack, author of Legal Reasoning and Legal System (which I've been trying to understand) and Regius Professor of Public Law at Edinburgh University is also a SNP MEP. Rebutting Michael Howard's "countries have constitutions" mantra he says,
“The Tories oppose any constitution, fearing it would make Europe into a country, a super-state even. But constitution does not imply country, in the case of the EU. In substance, the EU already has a constitution, but is not a country. If ‘constitution’ did entail ‘country’, then the game would already be up for the Tories. They would have to join the UKIP after all."