Is there a constitutional right to same-sex marriage? Or is there at least a constitutional right of homosexuals to be unburdened by a state constitutional provision defining marriage as a union between a man and a woman? Thanks to the Ninth Circuit Court of Appeals, which last week voided California’s Proposition 8, the Supreme Court may have to answer such questions in the not-too-distant future.

Anticipation of this event naturally induces speculation about its outcome, and because the philosophical lay of the land within the Court is so well known—four liberals, four conservatives, with Anthony Kennedy holding the balance—this speculation tends to take the following form: “What will Justice Kennedy do?” Indeed, as a number of commentators have noted, Judge Reinhardt’s opinion for the Ninth Circuit panel seems to be crafted with Justice Kennedy in mind.

Kennedy’s past opinions on related questions seem to indicate his openness to the constitutionalization of same-sex marriage, but the evidence is nevertheless equivocal. Kennedy authored Lawrence v. Texas, in which the Court struck down Texas’s law against homosexual sodomy, and in that opinion Kennedy permitted himself to wax somewhat indignant about the supposed irrationality of moral disapproval of such conduct. On the other hand, he also used that opinion to assure the nation, in the Court’s name, that the issues in that case had nothing to do with the question of same-sex marriage. As a result, Kennedy might not be so favorably disposed to a constitutional claim for same-sex marriage, since the advance of that cause has been for the last decade linked to the work of state courts that turned Lawrence’s reasoning precisely to the end that Kennedy and the Court disclaimed.

In view of these problems, as Matthew Franck noted in Public Discourse last Thursday, Reinhardt’s opinion seeks instead to assimilate the present case to Kennedy’s 1996 opinion for the Court in Romer v. Evans, which struck down a Colorado constitutional amendment that prohibited all levels of government within the state from treating homosexuality as a protected class under anti-discrimination provisions. As Franck observes, this case, too, is hardly a perfect fit for the cause. In Romer, Kennedy and the Court viewed the Colorado Amendment as an unheard-of innovation. Whatever the merits of that view, it would be difficult to say the same of Proposition 8, which simply restored the definition of marriage that had prevailed in California before the state supreme court decided to tamper with it.

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Neither Lawrence nor Romer, then, truly requires the Supreme Court to issue a right to same-sex marriage, and advocates of traditional marriage will do well—in light of Kennedy’s pivotal status in this case—to draw on everything in them that can resist such an outcome. Nevertheless, there is another aspect of Kennedy’s jurisprudential legacy that bears on this question and that should not be overlooked in finding arguments by which to persuade him to hold back from using the judicial power to redefine marriage. Justice Kennedy is famously associated with the joint opinion—put forward by himself, Justice O’Connor, and Justice Souter—in Planned Parenthood v. Casey (1992), in which the Court upheld the existence of a constitutional right to abortion. Although Kennedy was not the sole author of this joint opinion, he has subsequently referred to it with approval in later opinions authored only by himself, including in Lawrence v. Texas.

But the doctrine of Casey is clearly inconsistent with the view that there is a right to same-sex marriage. The Casey joint opinion explains that, although the supposed right to abortion is not to be infringed by the state, that right is nevertheless consistent with the state’s right to express its “preference” for natural childbirth. In other words, without forbidding abortion, the state may regulate it in such a way as to communicate its judgment that not having an abortion is the better option. In common sense, however, if a state may express its preference for natural childbirth without violating a woman’s personal right to abortion, it can surely express a preference for traditional marriage without violating the personal rights of homosexuals to live as they choose.

To be sure, because of the facts before the Court, the Casey opinion suggests only a limited way in which the state may express its preference for letting the unborn child live: by demanding the informed consent of the mother seeking the abortion, or, in other words, by requiring her to be made aware of the stage of development of her child, and the consequences of abortion for the child. In other words, the facts in that case only required the Court to acknowledge that the state could admonish a woman against having an abortion without in any way infringing on her right to have it if she wanted to. Nevertheless, no one could seriously deny that the state might go much further in actively encouraging the normal childbirth that it has a right to prefer. For example, a state law providing a tax credit or other benefits to mothers who carry their children to term and place them for adoption would be constitutionally unassailable.

A state that chooses to recognize marriages and to provide certain legal benefits for them, while not doing the same thing for homosexual unions, does nothing in principle different from the state that exercises its undoubted right to prefer and encourage natural childbirth over abortion. If we say otherwise, we must say that the right to same-sex marriage is somehow more fundamental, more to be protected, even than the right to abortion, a strange conclusion that Justice Kennedy would no doubt resist.

If the doctrine of Casey, which Kennedy had no small hand in crafting, is to be respected, then a state law that simply recognizes marriage while ignoring the conduct of homosexuals must be on solid constitutional ground. But Proposition 8 must be regarded as on even more solid ground than that. For California’s chosen mode of expressing its preference for marriage involves much less. California offers civil unions that provide homosexual couples with all the same material benefits as are provided to married couples. As has been pointed out before, the fight in California is entirely over the symbolic value of the term “marriage.” It is animated by the demand of homosexual activists not to equal benefits under law, but to equal recognition or equal public honor. In doing nothing more than reserving the traditional and venerated term “marriage” for heterosexual unions, the State of California is merely expressing its preference for such unions, without even encouraging them by means of legal benefits withheld from others. Surely it has a constitutional right to do something so minimal—again, if we are to remain consistent with Casey.

Lawyers arguing against Prop 8 might contend that the preceding arguments should fail because they confuse two areas of constitutional law. Casey was decided under the Due Process Clause, while the Prop 8 challenge is being brought under the Equal Protection Clause. Let us leave aside the obvious rejoinder that a law that merely expresses preference for or encourages a certain behavior—something the law does all the time—can hardly be said to deny anyone the equal protection of the law. In any case, the standards by which the Court evaluates claims under the Due Process and Equal Protection clauses in fact overlap. Liberal jurists have traditionally claimed that abortion, as a fundamental right, deserves the protection of “strict scrutiny,” meaning that laws regulating it must be regarded as constitutionally suspect and as justifiable only by a “compelling state interest.” Kennedy’s joint opinion in Casey backed away from this approach and held instead that laws regulating abortion must be subject to a less formidable “undue burden” standard. In either case, laws restricting abortion must, according to settled Court doctrine, be subject to some kind of heightened scrutiny. This is emphatically not the case with claims under the Equal Protection clause that do not involve suspect categorizations such as race or ethnicity, which laws protecting traditional marriage do not. Such cases are instead subject to what is called rational-basis review, which traditionally presumes the validity of the challenged law and places the burden of proof of its unconstitutionality on those challenging it. In other words, appealing to the different provisions under which these cases were heard only emphasizes the problem noted before: that the Prop 8 challenge asks the Court to treat same-sex marriage as an even more sacred right than abortion.

These are, admittedly, not the kind of arguments against a constitutional right to same-sex marriage that would be made in a more perfect legal world. It would be better if we could simply dismiss the idea as the constitutionally groundless invention that it is. But these are the kinds of arguments that might prevail with Justice Kennedy, which is the practical task before us if marriage is to be preserved in the present struggle.