Of the four dissenting opinions in today’s Supreme Court ruling on same-sex marriage, Justice Clarence Thomas’ is by far the most interesting and compelling. Thomas effectively argues that state recognition of marriage cannot be a form of “liberty” protected by the Due Process Clause of the Fourteenth Amendment because liberty only includes protection of individual rights against government interference, not the conferral of government benefits. His analysis has an important kernel of truth. But it ultimately fails to prove that laws banning same-sex marriage are constitutional.

The majority opinion by Justice Anthony Kennedy relies heavily on the notion that the right to marriage is a “fundamental” liberty protected by the Fourteenth Amendment, which therefore cannot be denied to same-sex couples. Thomas, however, contends that liberty does not include the conferral of benefits by the government:

Even assuming that the “liberty” in those [Due Process] Clauses [of the Fifth and Fourteenth Amendment] encompasses something more than freedom from physical restraint, it would not include the types of rights claimed by the majority. In the American legal tradition, liberty has long been understood as individual freedom from governmental action, not as a right to a particular governmental entitlement.

Thomas cites extensive historical evidence indicating that the liberty protected by the Due Process Clause was historically understood in this limited way. He is largely correct, both as to the historical meaning of “liberty” in the Due Process Clause, and with respect to the fact that the right to state recognition of marriage includes at least some components that don’t fit that understanding. For example, marriage often includes the right to certain tax and welfare benefits granted by the federal and state governments. These can hardly qualify as a form of liberty.

Still, Thomas’ analysis suffers from two important limitations. First, even if his argument is completely correct, it does not refute the more powerful Equal Protection Clause rationales for a right to same-sex marriage: that state laws that recognize opposite-sex marriage unconstitutionally discriminate on the basis of gender or sexual orientation. When state laws discriminate on the basis of suspect classifications such as race or gender, that discrimination is usually unconstitutional regardless of whether the laws in question grant positive benefits or not. For example, state governments can choose to provide or deny public education, as they wish. But it is unconstitutional for them to provide it only to whites or only to men.

The second flaw in Thomas’ position is that marriage recognition by state governments is not purely a matter of conferring positive benefits provided by the state. Marriage is also a contractual relationship between private parties, under which they take on various reciprocal obligations to each other. In most states that banned same-sex marriage before today, a same-sex couple could not sign an enforceable marriage contract, even if its content was limited to purely private marital obligations between the two parties.

And, as co-blogger David Bernstein and Ryan Williams have shown, the right to freedom of contract was, from early on, understood as an important element of the liberty protected by the Due Process Clause of the Fourteenth Amendment, and its analogues in state constitutions. The framers of the Fourteenth Amendment repeatedly referred to the right to make and enforce contracts as one of the basic rights of citizenship that they sought to protect by enacting the amendment. The right to contract was far from unlimited. One can argue about whether it should be construed broadly enough to include same-sex marriage. But it most certainly was part of the liberty protected by the Due Process Clause.

In his separate dissent, which Thomas joined, Justice Antonin Scalia suggests that entering into marriage is not really an exercise of freedom because “[f]reedom of Intimacy is abridged rather than expanded by marriage. Ask the nearest hippie.” Whatever “the nearest hippie” might say, freedom surely includes the right to voluntarily enter into a contract that restricts your future options. The right to enter in an employment contract is a form of liberty, even if it might restrict your choices about how to spend your time at work. Similarly, the right to enter into marriage is a form of liberty as well. In exchange for giving up your right to pursue certain kinds of “intimacy” with other people, you (hopefully) gain a relationship of tremendous value. Although some hippies might disagree, the right to make a binding commitment is a hugely important element of liberty. A person who can’t make such commitments – including in the sphere of marriage – is less free than one who can.

Not all the rights incident to marriage are an element of private contract. Some are indeed benefits conferred by the state. To that extent, Thomas is right that the objectives sought by same-sex marriage advocates cannot all be achieved through the Due Process Clause. But many rights incident to marriage are simply enforceable private contractual obligations that are as much an element of liberty as any other contractual rights.

Overall, I think the Due Process Clause argument for same-sex marriage is much weaker than the Equal Protection Clause argument. The majority would have done well to rely much more on the latter. Thomas’ insightful critique highlights some of the reasons why. But the Due Process Clause argument is not nearly as weak as he contends.

Thomas is also wrong to conclude that the majority “rejects the idea—captured in our Declaration of Independence—that human dignity is innate and suggests instead that it comes from the Government.” Here, he confuses the moral justification for dignity (which indeed exists outside of government) with the means for protecting dignity, which may indeed involve constraints on government action that degrades people and undermines their dignity. It is perfectly coherent to say that the right to enter into same-sex marriage contracts is an inherent one that exists apart from government and that governments infringe on human dignity when they deny that right or otherwise discriminate against same-sex relationships.

Thomas’ failure to consider the distinction between justification and enforcement is at the root of the weakest part of his opinion: the passage where he writes that “[s]laves did not lose their dignity (any more than they lost their humanity) because the government allowed them to be enslaved. Those held in internment camps did not lose their dignity because the government confined them. And those denied governmental benefits certainly do not lose their dignity because the government denies them those benefits. The government cannot bestow dignity, and it cannot take it away.” It certainly true that slaves and victims of unjust internment did not lose their right to dignity, which, as Thomas emphasizes, stems from their “inherent worth” rather than a decision made by the government. But it is pretty obvious that slavery and internment violated that right.

I am skeptical that the concept of “dignity” adds much to constitutional analysis that is not already better captured by the rights to liberty and equal protection of the laws – rights that, unlike dignity, are specifically listed in the Constitution. But Thomas’ critique of the majority’s dignity analysis is partly undermined by its own excesses.

Overall, Thomas’ dissenting opinion effectively exposes some key weaknesses of the Due Process Clause liberty justification for a right to same-sex marriage. But it fails to prove that laws banning same-sex marriage are constitutional.

UPDATE: I should note that Thomas goes wrong in one part of his opinion where he claims that the liberty protected by the Due Process Clause is limited to “locomotion” and “freedom from physical restraint and imprisonment.” Thomas provides little support for this claim, largely relying on a 1926 article by Charles Warren that has long since been superseded by more recent and more thorough historical research.

UPDATE #2: When I first put up this post, I missed co-blogger Sasha Volokh’s brief discussion of Thomas’ opinion in his thoughtful post earlier today. But I think Sasha misses some of the same points as Thomas himself. In particular, both ignore the way in which the right to marry is an element of freedom of contract, and therefore not simply a conferral of government benefits.