Matters can appear very complicated. Many commentators make matters unnecessarily confused by refusing to consider what sovereignty actually is before they start commenting. Instead they will have an idea of what ought to happen and then propose their own definition of sovereignty in their discussions. But really sovereignty is not an elusive or nebulous idea at all. It is in fact quite simple, and the simple concept is sufficient to illuminate the issues.
Sovereignty is really a feudal or imperial concept.
A ruler is sovereign over those matters which he can determine simply by choosing that they should be so. This may seem rather archaic and irrelevant but we can make the concept of sovereignty very clear by considering just two examples from the feudal hierarchy. First God's sovereignty. When theologians say that God is sovereign what they mean is precisely that God can make anything happen simply by choosing that it should happen. In the feudal system God's sovereignty is universal and absolute.