You're right, it's not about sovereignty, it's about protecting the few assets we have left.
Scotland is responsible for 70% of the fishing which is allocated to members of the EEC, yet it has no say over these allocations.
Our fishermenm are going out of business daily, while Spanish, and others, catch right up to our shores, and send the fish directly abroad by road. The lorries which carry them arrive here with full fuel tanks, and almost never buy fuel at our inflated prices, so Scotland derives a nil benefit from these activities.
The UK heavy industries have been decimated through the activities of this hydra in Brussels, and all the money we have received in grants etc from there, wouldn't pay for half of the assets we have lost.
Where is our quid pro quo?

JM