I read International Relations at university and spent three happy months at Wolfson College, Cambridge, researching and writing a paper on ‘Attitudes to Sovereignty in Europe.’ So I find listening to the Brexit debate in the UK very frustrating.
We have to remember that sovereignty means different things to different people, and if we don’t use it in its proper sense, then one side wins the argument before it has started.
Sovereignty is not the same as power or independence, so letting others fish in UK waters is not a loss of sovereignty; because the UK allowed it and negotiated it in return for something else. Something like, access to markets for its fish, or the right to fish in another country’s waters or a better trade deal. This is the kind of decision that only a sovereign nation can make, it makes its own political decisions to its own advantage. If it changes its mind it can leave the organisation responsible, re-negotiate the deal or even end it and enforce those decisions.
You can say the same about any deal or membership of any organisation; the UN, ECHR, NATO, the International Postal Union or whisper it who dares, the EU.
A sovereign country does not lose its sovereignty just because its trades total isolationist independence to its advantage. If that was the case every country in the world except for N Korea would have lost its sovereignty centuries ago.