I don't agree with all of Delmar's views, but ANY law is an act of violent force, to enforce some type of morality, whether a right view of morality or a wrong one.
Our laws are backed up by the threat of retribution as a means of oppression/coercion. Force is only used in response to resistance. And violent force is only used in response to violent resistance. This is the functional methodology of what we call "law", and in most cases a state of lawlessness will be far more oppressive/coercive and violent than the rule of law by a social consensus.
Human beings cannot live together and remain totally free. Sacrifices, accommodations, and compromises have to be made for us to live together in peace, harmony, security and prosperity. So the goal is to obtain a reasonable and functional balance between the freedom that's sacrificed, and the freedom that's achieved and protected; and the needs and desires of the individual, with the needs and desires of the social group (family, clan, village, county, state, nation, and/or species).
As a libertarian, I believe in using legal force ONLY to prevent acts of violence against other people or their property. I don't believe it is the job of Christians to enforce all elements of the OT legal code, but only those precepts which prevent men from violating the rights of other men. This is where I disagree with theonomists.
You seem to be very confused about what constitutes violence, what constitutes force, what constitutes oppression/coercion, and why the rule of law is essential to human society. You also seem to have an inordinately inflated idea of 'property', for some reason.
But let's not kid ourselves about laws being an enforcement of morality.
Whether or not a law "enforces morality" is mostly just coincidental. If you think murder is "immoral", of example, and there is a law in your society against murder, then you may think the law is "enforcing your morality". That is, you might think that if you're rather self-centered and small-minded. But in fact, the law may well have nothing to do with enforcing your or anyone else's morality. It may well have been written solely for the purpose of maintaining peace within the society of humans you live amongst. Period. And the fact that it aligns with your personal moral proclivities is just coincidental.
And in the United States, as in most modern nations of the world these days, this is exactly the case. Most laws are written and are enforced solely for the purpose of maintaining peace and stability within the various societies of humans that make and enforce them. They are not intended to promote any particular moral view, and the fact that they may or may not do so is just happenstance.
You have tied yourself into an absurd position where you don't even believe morals exist, and you don't think laws should "enforce morality" yet I suspect you support more laws than Delmar does.
I have never stated that morality does not exist. I have never stated that laws don't coincide with some people's moral views. I have only tried to point out that in modern societies such as our own, the laws are not written nor enforced for moral reasons. They are written and enforced for the purpose of maintaining the peace and security of the society of humans we are living with.
If there is a marriage contract than adultery, it seems to me, would be a violation of said contract, even using purely secular reasoning.
And it is considered a breach of contract, by law. That's why divorces often involve legal procedures for a resolution.
The question, in my mind, would be whether the victim of such actually wants to go to the courts or not. They may well not wish to do so. Also, its really hard to prove.
Some people do, some people don't. I don't see why this is an issue for you.