There's also something to be said about the progressive revelation of the Law and how much of revelation we should enforce. The Christian ideal of the New Testament is different (and more strict in some ways - cf polygamy) than The Law revealed to Moses, which is more strict than the commandments given to Noah which are held to be for all the human race. Civil law certainly shouldn't enforce constraints against divorce when the Mosaic law allowed for it, despite well-considered Christian disapproval. The nations are a law unto themselves, but our ideas of what that law are might not always be what we think.
I'll say what is to be said about "the progressive revelation of the Law". The idea that revelation is continuing to progress is not Orthodox. Christ has come to this world and given it the Ultimate revelation. There will be no new revelation changing our understandings of things, and it is heretical to think otherwise. Dogma clarifies established truth; it doesn't add or discover new truth.
The Christian ideal is more strict in every way, as it means we are to strive to not merely follow a set of laws and then be a-OK, but to strive to become like Christ Himself. Love your enemy and turn the other cheek is more difficult than simple dietary restrictions or even OT rules on sex and marriage.
Civil law can be whatever people manage to make of it. If we can manage to make the law Christian, then divorce ought to be difficult. The Christian ideal is to not divorce at all. Ever. For any reason. Yes, Christ allowed the exception. But again, not as the ideal, but as the allowance for the hardness of our hearts. But if civil law may reflect Christian morality on what is allowed, divorce will STILL be difficult, and generally speaking, only for infidelity.
As to what we should enforce, we should teach people what marriage is meant to be, and law will reflect that. It's no good teaching that marriage is an indissoluable union and then say that in civil life, people may do whatever they want. Let them think more carefully about getting married. People need the guidance of Tradition and wise law, that proceeds from a thing that knows better than they what is good for them. And for their children, about whom we are so quick to forget in all these discussions.
In general morality, as opposed to worship and practice, if we DO have power in society, as rulers, either through being a monarch, tsar, or president, or if the vote actually represents power (which it most often does not), then we OUGHT to demand law that actually supports morality. It's not forcing Christian faith to tell people they must obey a particular moral code in law, that they may be punished for cursing or drunkenness or lewdness in public. Even Caesar could legitimately tax people; he just had no right to force worship.
