While Paul’s idea is interesting from a theoretical perspective, there is a perfectly rational reason that government has given a privileged position to marriage in the first place. Traditional families have been integral to the formation of society and human beings are social animals. In times of need, people have historically turned first to family. The raising of children, emotional and economic support and other social benefits derive from the traditional family. If we do away with this, the need will remain and people will demand that an ever larger government fill the role of economic, emotional and social support that is now provided by the family. I doubt this is Paul’s desired outcome.
A problem is that with LBJ’s “Great Society” and welfare, which replaced a parent with a government paycheck, that ship sailed a long time ago.
One cannot really run a society on pure libertarian principles. It just won’t work.
Eventually, the “shoulds” and “oughts” of human life will get in the way.
The moment you have LAWS, you are implicitly admitting that certain moral principles must be adhered to by society whether individuals like it or not.
And these LAWS will depend on what Moral Values ( i.e. First Principles ) society adheres to. It can be informed by Christianity, Islam, Buddhism or Atheism, but you cannot escape or avoid adhering to something.