Just when you thought the U.S. Supreme Court was a distant memory of spring, the briefs are in for the blockbuster affirmative action case coming in October. It involves a student claiming she was denied admission to the University of Texas because she is white.Nobody is prepared to tell the court the real reason we still need affirmative action: It would be shameful madness to recruit and train an elite that included only a handful of blacks and Latinos. Instead, the core argument for retaining some element of affirmative action in admissions is "diversity."The Obama administration and the universities claim that diversity is beneficial because it enhances the educational experience in the classroom for all the students, not that it serves a vital political function.The idea is that pedagogy will gain immeasurably and incalculably (double meanings intended) from the expression of different perspectives.The friends of the court can hardly be blamed for adopting the educational diversity rationale. It is, after all, the law of the land, expressed by Justice Sandra Day O'Connor in the 2003 Grutter v. Bollinger case and rather hopefully couched in the prediction/promise that it would last just another 25 years. In addition to precedent, the diversity case for admission policies has the virtue of not acknowledging the original rationale for affirmative action: restorative justice for blacks and Latinos, who as recently as the 1950s were legally barred from many universities. In a world where Barack Obama is U.S. president, it is easy to believe that educational racism is history -- or that past efforts to fix it have somehow succeeded.Yet the Obama era can also point us to the true societal reason we still need affirmative action: We are a country run in no small part, though not exclusively, by a meritocratic elite.The universities are important filters shaping that elite. Their idea of merit relies heavily, though not exclusively, on grades and standardized tests. (Don't get me started on legacy admissions or lacrosse players.) Yet if these yardsticks were the whole ball of wax, there wouldn't be enough blacks and Latinos to populate that elite in any vaguely appropriate proportion to the population.If some 30 percent of Americans were seriously underrepresented in the upper echelons of society, what would that make of our claim to be the land of opportunity -- or of equal justice under law? A more cynical observer might add that it is extremely difficult to run a country, democracy or no, if a third of the citizens feel excluded from governance. Seen from this perspective, affirmative action is a social necessity.Even if we could be governed by an elite that didn't look like America, would it be right? Meritocracy fits poorly with democracy if the meritocrats aren't representative. The problem isn't that unrepresentative universities wouldn't be democratic. It's that governance by the elites they produce would be.The crucial question for the Supreme Court, then, is whether it is prepared to be the agent of a formal equality that would seriously disrupt the way a diverse meritocratic elite is now chosen. The deans of the Harvard and Yale law schools hint at this point in their own two-person brief when they point out that every sitting justice went to one of their schools. In an earlier era, such a lack of educational diversity would have been considered outrageous. Today, we rely on the educational institutions to do the diverse elite selection for us -- so that today's court includes Justices Clarence Thomas and Sonia Sotomayor, two Yale Law School-educated nonwhites.Five justices may decide they don't mind overturning our entire meritocratic system. If they do, our elite-producing institutions will face a crisis. Either they will have to find new ways of creating social diversity, or we will have to stop using them to make the meritocrats who govern us.Noah Feldman, a law professor at Harvard University and the author of Scorpions: The Battles and Triumphs of FDR's Great Supreme Court Justices, is a Bloomberg View columnist.