People have opined that shadow laws that run parallel to normal jurisdiction like Sharia are bad. I agree – it must be one law for all. Introducing a competing law for one part of the population is an incredibly stupid idea. Judging a person by two different set of rules undermines everyone’s belief in justice: if the same deed results in more than one possible sanctions, something is wrong with your system. If everything results in the same, they are the same system, and no second set of laws is required.
What bugs me most, though, is that the most vocal proponents of shadow sharia law are really advocating something else: They want one law for believers, one for infidels, and none for themselves.