What is Sovereignty?

In reading Canadian Aboriginal rights jurisprudence, the central role that judicial acceptance that the British Crown was, and is, sovereign plays in Canadian law and politics becomes crystal clear. Before one can make such an assertion, however, once has to address the fundamental question that lies behind the assertion — what is sovereignty? Is there a principled definition of what “sovereignty” is that allows sovereignty to exist in a society governed by the rule of law? Or is sovereignty merely a legal fiction, created to provide an ex post facto legal justification for what is, in truth, merely an exercise of raw power? And if it is a concept that can exist in conjunction with the rule of law, how is sovereignty legally acquired and secured?