On Thursday afternoon, the United States Court of Appeals for the Sixth Circuit just became the first federal appeals court in the country to side with marriage discrimination. Although the immediate effect of this court’s 2-1 decision is that marriage equality will not quickly become the law in Michigan, Ohio, Kentucky and Tennessee, the most important consequence of the Sixth Circuit’s holding is that there is now a “circuit split” on the question of whether same-sex couples must be allowed to marry under the Constitution. A circuit split, which occurs when two or more federal appeals courts disagree on the same question of law, is one of the most common reasons that the Supreme Court agrees to hear a case. Thus, the Sixth Circuit’s decision on Thursday all but guarantees that the justices will decide whether the Constitution’s promise of equality extends to gay people in all 50 states.

To date, the Fourth, Seventh, Ninth and Tenth Circuits have all sided with equality, along with nearly every single federal trial judge to consider the question after the Supreme Court struck down the anti-gay Defense of Marriage Act in 2013. Moreover, the Supreme Court has stood aside and allowed the federal appeals court decisions supporting marriage equality to take effect. The momentum is clearly against discrimination, and Judge Jeffrey Sutton’s opinion for the Sixth Circuit shows a keen awareness of this fact. His decision reads like the Custer’s Last Stand of judicial opinions. In it, he tries to anticipate every single legal argument that can be raised in support of marriage equality, and then he attempts to bat it down.

To the justices who concern themselves with how the Constitution was understood at the time it was written, Sutton warns that “[n]obody in this case . . argues that the people who adopted the Fourteenth Amendment understood it to require the States to change the definition of marriage.” To those who worry about the legacy of anti-gay animus in the United States, he claims that bans on marriage equality “codified a long-existing, widely held social norm already reflected in state law.” To those that fixate on tradition, Sutton writes that “a State might wish to wait and see before changing a norm that our society (like all others) has accepted for centuries.”

According to longstanding Supreme Court precedent, however, groups that have historically been subject to discrimination that has little basis in their ability to “perform or contribute to society” enjoy heightened protection against discrimination under the Constitution. Sutton concedes the legacy of discrimination against gay people, yet he discounts its relevance to this case. His explanation for why is worth quoting at length:

We cannot deny the lamentable reality that gay individuals have experienced prejudice in this country, sometimes at the hands of public officials, sometimes at the hands of fellow citizens. Stonewall, Anita Bryant’s uninvited answer to the question “Who are we to judge?”, unequal enforcement of antisodomy laws between gay and straight partners, Matthew Shepard, and the language of insult directed at gays and others make it hard for anyone to deny the point. But we also cannot deny that the institution of marriage arose independently of this record of discrimination. The traditional definition of marriage goes back thousands of years and spans almost every society in history. By contrast, “American laws targeting same-sex couples did not develop until the last third of the 20th century.” This order of events prevents us from inferring from history that prejudice against gays led to the traditional definition of marriage in the same way that we can infer from history that prejudice against African Americans led to laws against miscegenation. The usual leap from history of discrimination to intensification of judicial review does not work.

Sutton is probably correct that marriage discrimination did not emerge in the same way that Jim Crow laws did. Jim Crow was part of a conscious and comprehensive effort to reduce African Americans to second-class citizenship. Laws excluding same-sex couples from the blessings of marriage, by contrast, were not always enacted with such conscious intent. But even if Sutton is correct that marriage discrimination was not enacted with the same conscious intent as Jim Crow, it is hard to see why that justifies weakening the Constitution’s promise of equality. Why does anti-gay bias become less harmful or less invidious because it was, until recently, so tightly woven into American culture that it would never have occurred to generations of Americans to extend equal rights to gay couples?

Discrimination, moreover, is does not become constitutional simply because it was enacted for relatively benign, or even benevolent, purposes. Many of the early cases challenging gender discrimination, for example, targeted laws that were intended to protect women or even place them on a chivalric pedestal. Craig v. Boren, which is arguably the Supreme Court’s most important gender discrimination case, struck down a law that discriminated against men. It is difficult to argue that the Oklahoma lawmakers who enacted that law did so because they were biased against males — especially because the law was enacted at a time when it was difficult for women to be elected to public office.

In any event, Sutton’s opinion is likely to be reversed by the Supreme Court. It is very unlikely that the justices would have allowed other court decisions siding with marriage equality to take effect unless they believed that there are five votes on the Court to extend marriage equality throughout the land.