But-for sex: equal protection and the individual right to marry a specific person without regard to sex.

• Author: Clark, J. Stephen
• Position: Symposium on LGBT Rights

When California's notorious Proposition 8 came before the United States Supreme Court two years ago, (1) Justice Kennedy made a potentially significant remark about discrimination against same-sex partners. When the oral argument turned to the appropriate level of equal protection scrutiny for classifications based on sexual orientation, Kennedy interjected, "Do you believe this can be treated as a gender-based classification? ... It's a difficult question that I've been trying to wrestle with." (2)

Kennedy was recurring to a longstanding legal theory characterizing the exclusion of same-sex partners from civil marriage as a sex-based classification. Ironically, this theory was first articulated by traditionalists opposed to same-sex marriage. In the 1970s, they used it to argue against ratification of the federal Equal Rights Amendment, (3) which would have required probing judicial scrutiny of governmental actions based on an individual's sex. (4) The sex-discrimination theory re-emerged in 1993, when the Hawaii Supreme Court affirmatively adopted it as the rationale for closely scrutinizing the exclusion of same-sex partners from civil marriage. (5) Since then, the theory has played a supporting role in other constitutional challenges as an alternative basis for invalidating the same-sex exclusion, (6) as in a federal ruling now on appeal to the Eighth Circuit. (7)

Kennedy's uncertainty about the theory is understandable. The exclusion of same-sex partners from civil marriage harms those lesbians, gay men, and bisexuals who wish to marry a same-sex partner, so one is apt to assume that the exclusion classifies on the basis of sexual orientation, not sex. When same-sex partners are excluded from civil marriage by a law that authorizes only opposite sex marriages--such as South Dakota's constitutional stipulation (8)--or by one that disallows same-sex marriages--such as the state's statutory exception to its policy of interstate recognition (9)--the intuitive reaction is often that the law discriminates against gays and thus classifies on the basis of sexual orientation. A law of this type does not look exactly like the kind of laws that the Court has deemed sex-based classifications. It seems different from such sex-based classifications as the exclusion of women from the Virginia Military Institute (10) or the adoption of different ages of majority for women and men. (11) The sex-based disparate treatment of women and men is manifest in those kinds of governmental actions, whereas any sex-based disparate treatment in the exclusion of same-sex partners from civil marriage is less obvious and thus more contestable. In an analogous context, for instance, Justice Scalia argued that a sodomy ban applicable only to same-sex partners did not facially classify on the basis of sex because "[m]en and women ... [were] all subject to its prohibition of deviate sexual intercourse with someone of the same sex." (12) It is not surprising that Kennedy has been uncertain whether the exclusion of same-sex partners from civil marriage can be viewed as a sex-based classification.

Nevertheless, as I have argued previously, (13) the answer to Kennedy's question is yes. Not only can the exclusion of same-sex partners from civil marriage be viewed as a sex-based classification, but that theory is actually the best way to view the exclusion, the way most consistent with existing equal protection doctrine. Critics of the theory, including Scalia, have generally rejected it only by contradicting the fundamental premise that equal protection is an individual right to a specific opportunity, not a guarantee of group-based parity. Whenever the government makes an individual's sex the but-for cause of a denial of a specific opportunity, the denial is a sex-based classification, which triggers intermediate scrutiny (14) and requires an "exceedingly persuasive justification." (15) As I shall explain, the exclusion of same-sex partners from civil marriage also triggers that standard of review because it denies an individual, because of her sex, the unique opportunity of marrying the specific person she loves.

1. THE INDIVIDUAL RIGHT TO EQUAL PROTECTION

   Even if the exclusion of same-sex partners from civil marriage seems different from more obvious kinds of sex-based classifications, one fundamental principle of equal protection law clarifies how the same-sex exclusion also qualifies as a sex-based classification. This basic principle is that equal protection is not a collective right, but an individual one. (16)

   As Chief Justice Roberts has observed, the Equal Protection Clause "'protects] persons, not groups."' (17) The text itself provides that "[n]o state shall ... deny to any person within its jurisdiction the equal protection of the laws." (18) The protection accrues to "any person"--singular. (19) '"At the heart of the Constitution's guarantee of equal protection,"' Justice Kennedy has observed, "Ties the simple command that the Government must treat citizens as individuals, not as simply components of a racial [or] sexual ... class.'" (20) The focus of analysis is the individual.

   As applied to sex, equal protection gives an individual the right to be free from unjustified legal detriments imposed on account of such individual's sex. In Davis v. Passman, (21) for instance, the Court held that an individual woman, who was fired as a congressional staffer solely because of her sex, established a prima facie denial of equal protection so as to trigger heightened scrutiny of her discharge. (22) Equal protection conferred upon her "a federal constitutional right to be free from gender discrimination which cannot meet [the] requirements" of heightened scrutiny. (23) The Court elaborated that "[t]his right is personal; it is [the individual woman], after all, who must suffer the effects of such discrimination." (24) This basic principal that equal protection is an individual right is the lodestar to keep in clear sight when considering whether the exclusion of same-sex partners from civil marriage constitutes a sex-based classification.

   One way to keep that lodestar in sight is to put the analytical focus squarely on one individual. A perfect example is Kaitlynn Hoerner. She is one of the plaintiffs in the pending challenge to South Dakota's exclusion of same-sex partners from civil marriage. (25) She met her same-sex partner, Krystal Cosby, in 2012. (26) Kaitlynn lives with Krystal in Aberdeen, South Dakota, where they are now raising a daughter who was bom to Krystal. (27) Kaitlynn applied for a license to marry Krystal, but the application was rejected under South Dakota's same-sex exclusion. (28) Kaitlynn has now challenged that rejection as a denial of equal protection. (29) Kaitlynn has an individual right to be free from unjustified legal detriments imposed upon her by the government on account of her female sex. Indeed, one may disregard all the other South Dakotans who have been denied marriage licenses under the same exclusion and imagine Kaitlynn's claim as if she had brought only an as-applied challenge.

2. THE BUT-FOR TEST

   The key question is whether the detriments that Kaitlynn suffered--the rejection of her application for a marriage license, the attendant refusal to allow her to marry her chosen partner, and myriad incidental burdens--were imposed upon Kaitlynn on account of her sex. The answer is yes. A detriment is imposed upon an individual on the basis of sex whenever that individual's sex was a but-for cause of the imposition. When that condition is true, the detriment is a result of a sex-based classification and thus triggers heightened scrutiny.

   Although the Court has not had much occasion to elaborate on the nature of the causation necessary to trigger heightened scrutiny, it has said enough to make clear that the standard is but-for causation. The Court said as much in one of its leading sex discrimination decisions, Mississippi University for Women v. Hogan. (30) That case involved a challenge to the refusal of a single-sex public university, Mississippi University for Women (MUW), to allow Joe Hogan, a locally employed male nurse, to take classes for credit toward an advanced degree because formal enrollment for credit was restricted to women. (31) The Court held that the refusal to allow Hogan to take classes for credit constituted a sex-based classification that triggered heightened scrutiny. (32) In reaching that conclusion, the Court manifestly used the but-for concept of causation.

   In explaining why the refusal triggered heightened scrutiny, the Court elaborated that Hogan would suffer at least two tangible detriments because of his sex. (33) First, if he wanted to take nursing courses for credit, he would have to drive some distance to another state nursing program that was coeducational. (34) A "similarly situated" woman would not have faced that inconvenience because she could have enrolled at MUW and avoided the driving. (35) Second, the distance meant that Hogan could not take nursing courses for credit while continuing to work full-time in the particular nursing job he held. (36) His female co-workers, in contrast, could do just that. (37) They thus "had available an opportunity, not open to Hogan, to obtain credit for additional training[,]" because they could simply enroll at MUW while continuing to work in their existing jobs alongside him. (38) Denying Hogan the opportunity to take courses for credit thus constituted a sex-based classification because it imposed upon Hogan '"a burden he would not bear were he female.'" (39) This language was key; it was the but-for test. Hogan would not have experienced these particular detriments but for his being male.

   This portion of the Hogan opinion also illustrated the precise operation of the but-for test. It required imagining a hypothetical situation in which Hogan's sex was different, but everything else remained exactly the same. (40) With...