An opinion poll in Britain has revealed that 40% of British Muslims favour the introduction of sharia law in parts of the UK. It might surprise people to know that I actually agree. The reasoning, however, is quite complicated and is not because I have any sympathy with sharia law.
John Rawls, perhaps the most influential political philosopher of last century, argued that we all have different values but that, given that fact, we could still all live together in a liberal democracy. He argued there are certain things we want, whatever else we want, including certain freedoms and so on. This was called a thin theory of the good. Islam, however, has what I would call a thick theory of the good. Indeed, it is so thick it is not compatible with other people's theories of the good.
If Britain was a country of first-generation immigrants, we could reasonably say that they should live by our rules. Unfortunately, huge numbers of British Muslims were born there. It is their home. Surely they should have the opportunity to live as full a life as they can. If they are true Muslims, who wish to live by sharia law, and their goods and go to end most deeply held beliefs require living by sharia law, I think there should be a place for them in the country of their birth.
There are certain areas in Britain, that are almost exclusively Muslim. I see no harm in allowing at least one of these pockets to become a semi-independent Muslim state. The less insular Muslims could live somewhere else, while those who really wanted to live under sharia law could live there.