The concept of sovereignty will certainly feature in the debate concerning E.U. membership.
It's always useful to provide an early definition of central terms in any discussion.
Osborn’s Concise Law Dictionary 12th Ed. 28 February, 2013 – available to all current OU students through the Westlaw database – provides a very helpful definition of sovereignty that reveals the context-sensitive nature of sovereignty:
Sovereignty
“The supreme authority in an independent political society. It is essential, indivisible and illimitable (Austin). However, it is now considered both divisible and limitable. Sovereignty is limited externally by the possibility of a general resistance. Internal sovereignty is paramount power over all action within, and is limited by the nature of the power itself. In the British Constitution the Sovereign de jure is the Queen or Crown. The legislative sovereign is the Queen in Parliament, which can make or unmake any law whatever. The legal sovereign is the Queen and the Judiciary. The executive sovereign is the Queen and her Ministers. The de facto or political sovereign is the electorate: the Ministry resign on a defeat at a general election”.
(The Austin referred to is John Austin (1790 - 1859) the English legal philosopher whose book on jurisprudence, published in 1832 - the year of the Great Reform Act, is one source of traditional thinking on sovereignty)