But, to give it its full name, Magna Carta Libertatum (my italics - I don't think they had 'em back then) gets it the right way round. It was in some respects a happy accident. In 1215, a bunch of chippy barons were getting fed up with King John. In those days, in such circumstances, the malcontents would usually replace the sovereign with a pliable prince who'd be more attentive to their grievances. But, having no such prince to hand, the barons were forced to be more inventive, and so they wound up replacing the King with an idea, and the most important idea of all - that even the King is subject to the law.