EU

To determine whether the country should be in the EU, you have to weigh the pros and cons for the taxpayer. 

Freedom of movement, some tech and food regulations (like the charger standardisation) and freedom of trade are positives. 

I don't know what the EU demands of members, to really know if membership is worth it. I don't know enough about the possible bad, but I'd study them and, of course, check with the two councils. I have heard of the EU scattering migrants across Europe, which could be a bad for the taxpayer.

Sovereignty alone isn't a good enough reason, because the bad and the possible bad might be outweighed by the good. Clearly, it's hard to tell, because of how tight the EU membership referendum was.

You have to remember that if someone speaks of sovereignty as a reason for not being in the EU, what they might really want is more power for themselves, and aren't meaningfully trying to empower the people.