Let me hop in here for a comment turned post.
The W2K positions sounds great if you are Daniel in Babylon or even a Christian serving in the Chinese government. But is this our situation?
Rather, we in the West have a right to appeal both to nature and the Decalogue because the Decalogue is historically woven into the fabric of the Anglo-American cultural, legal, and political tradition. Maybe we cannot point to an unbelieving neighbor and say that abortion is wrong because God says so… not very convincing to an unbeliever I suppose but we can certainly point to the revealed law of God as it has been historically recognized and taken into account by our legal tradition.
What I am saying is that W2K is sound on an abstract basis but when applied it must take into account the role that Christianity has played in shaping the culture WE (not Daniel or Joseph) actually serve within.
Christendom still has some clout around here (and this is am objective reality whether Reformed theologians it is a good thing on theoretical basis).