In the UK, both sovereign and subject are bound by 820 years of the Common Law, a system that is taken for granted, and understood by few. I have chosen three quotations to explain how important it is to understand the differences between Common and Civil Law as the differences are not about law, but about a system that has created the culture in which those in the Anglosphere live. That culture is under threat on both sides of the atlantic.
Rulers don't like Common Law as it gives individuals rights and thus rulers seem determined to undermine it. Rulers like Civil Law as through it they can control its citizens rather than allow its citizens control of the state. In the UK we have just had our first trial without jury. The European Arrest Warrant allows people to be taken from the UK with no examination of the evidence, no right of appeal, just on the say so of another European court. Habeas Corpus is dead.
Also, Common Law breeds individualism that can flourish in a spirit of freedom. Great men and woman have grown in this culture of freedom. Civil Law breeds or rather forces conformity. Individualism is frowned upon and even repressed.

The answer, of course, is very little.
