Interesting, and possibly problematic.
I'm no lawyer but it seems to me that the legal bases against imposing local sharia are overwhelming. I cannot open a little chattel slavery enclave in North Lafayette. There is a clear stance for freedom, and that is the benefit of a written constitution; those wronged can claim their Constitutional rights. Canada and (other) European nations frequently lack the clear delineation.
My concern is the multiculturalists who will refuse to go to court to protect a Muslim girl's rights. We can fight to take down the Easter Bunny (Cuniculine, patriarchal bastard!) but if enough people sit still while a young girl has to wear a hijab, or honor killings are enforced, than this enclave could happen.
In a way, it would be an interesting test of the Left that Christopher Hitchens left. Would they place women's rights and gay rights above multiculturalism?