Toward the end of March, libertarian Republican Rep. Justin Amash of Michigan tweeted that the "[r]eal threat to traditional marriage & religious liberty is government, not gay couples who love each other & want to spend lives together." The comment prompted a Twitter exchange with Jennifer Bendery of the Huffington Post about the Defense of Marriage Act, which Amash supports repealing. Amash's spokesman later explained the congressman's position that the government should not be involved in marriage at all:

"I think in his ideal world, the governments – at all levels all together – would get out of marriage," [spokesman Will] Adams told HuffPost's Chelsea Kiene on Wednesday. "Much like we don't want the government involved in my church's communion or we don't want the government to regulate my church's baptism, we don't want to have government regulate another sacrament in my church, which is marriage. That's then his position."

Getting the government out of marriage entirely is a fairly common libertarian solution to the thorny question of recognizing non-traditional relationships. It's seen as a path for helping simplify a complex tax code that results in absurd incentives and penalties. It robs the state of its paternalistic authority to put its stamp of approval on private relationships and places them firmly in the hands of citizens.

But as a legal matter, separating marriage from the government entirely may be just too much, at least in the United States. Helen Dale, a three-time fellow at the Institute for Humane Studies and a classical liberal trained in different types of legal systems, wrote a brief in defense of same-sex marriage recognition for the Reason Foundation (the non-profit that publishes Reason.com and Reason Magazine). As a "libertarian aside" in her brief (pdf), she detailed how America's significant use of common law in family courts—that is, the accumulation of case law built up over years of precedents—may be a huge hurdle to such a broad libertarian goal:

[I]t may just be more difficult to privatize marriage in any common law jurisdiction. At common law, the law of marriage and the family is part of public law — and always has been — even when in the hands of the Church. This is why there was no 'common law marriage' in England. In civilian countries, by contrast, family law is private law, and thus much more amenable to manipulation via private law mechanisms. That is why there was 'marriage by habit and repute' in Scotland.

Dale, who lives in Edinburgh, Scotland, compares England and Scotland to demonstrate the differences between common law (as practiced in America and England) and civil or Roman law (as practiced by Scotland), which relies more on legislative statutes and not legal precedents determined by case rulings. In a phone interview, Dale said such distinctions are important because of America's use of common law. Libertarians may see privatizing marriage as simplifying and liberating the system. But the reality may end up being the opposite. She sees the difference between common law and civil law and warns of huge consequences for those who do not.

"Common law of contract has built up over thousands of years," she said. "It's not just something you can sweep away. It's very expensive, very awkward. It leads to lots of litigation and pain. All the people who advocate for this need to go into it with their eyes open and be aware of how much change is involved. There would be fundamental changes to families and contracts."

For example, Dale asked, what would happen in a system where marriages were treated as entirely private contracts if a couple decided to enter in a relationship defined by Sharia Law? What would happen if parts of the contract contradicted rights recognized by constitutional precedents or case law?

Richard Epstein, libertarian legal scholar at University of Chicago and New York University and author of Simple Rules for a Complex World, also argued those who want to completely privatize marriage do not appreciate the severity of the legal tangles that would arise. At the conservative-libertarian blog Ricochet, Epstein responded recently to a column at National Review Online about serious legal consequences when the government is unable to clearly track relationships between people:

One notable gap in the [John] Fund column was any reference to the status of children of this union. That covers issues dealing with child support and inheritance rights. It also deals with issues of guardianship and divorce. It is hard enough to deal with these questions when it is known who is married to whom. It is even harder to deal with them when the nature of these private relationships resists standardization. Things do not get any easier when the subject turns to external attribution rules that are commonly tied to spousal status. Do your shares and mine count as a single holding sufficient to create a control block under tax or securities law? Or are they to be considered separately so that this designation cannot be applied? What about reporting rules for various kinds of conflict of interest situations in business or biomedical research? If there are intermediate statuses that people can adopt, all of these external groups are going to have to develop criteria to apply their own provisions. It will prove to be messy, costly, and inefficient.

Epstein's preference is to expand legal recognition to include same-sex partners and even potentially polygamous relationships, not to try to completely change the relationship between laws and families.

In a phone interview, Epstein expressed frustration at libertarians pushing such extreme changes without considering all the consequences.

"A libertarian has to sort-of understand that he's not making it in a first principles world," Epstein said. "We can make the world more libertarian in general by opening the licensing procedure."