This is the seventh in a series about the oral argument in ​Shelby County v. Holder.

Much ink has been spilled ​over a number of what I view as minutiae over the oral argument in Shelby County v. Holder. But there's one significant question at stake, so far mostly undiscussed: what standard of review should apply?

Without getting into the weeds (and grossly oversimplifying some of the principal cases), there are three major schools of thought as to how the Supreme Court should evaluate Congress's exercise of power under the Fourteenth and Fifteenth Amendments. The first is essentially rational basis, or a deferential "necessary and proper" view, first articulated in McCulloch v. Maryland​ in 1819: "If the end be legitimate, and within the scope of the Constitution, all the means which are appropriate, which are plainly adapted to that end, and which are not prohibited, may constitutionally be employed to carry it into effect."

The second is a more exacting review, "congruence and proportionality."​ In City of Boerne v. Flores​ in 1997, the Court concluded that the Fourteenth Amendment was "remedial, rather than substantive," which limited the scope of ills that Congress could address: "The appropriateness of remedial measures must be considered in light of the evil presented."

The Court identified these two standards in Northwest Austin. And the third is perhaps idiosyncratic. Justice Scalia in Tennessee v. Lane rejected his previous use of the "congruence and proportionality" standard. His test would find that Congress may "enforce" the tenets of the Fourteenth Amendment but not enact prophylactic legislation.

Complicating this is that there has been a great deal of application of "congruence and proportionality" under the Fourteenth Amendment, but it's largely been resisted under the Fifteenth Amendment, particularly as the test is of relatively recent vintage.​ Apart from the dispute of which standard to apply to the Fourteenth Amendment, then, is what to apply to the Fifteenth Amendment.

We can perhaps glean some hints as to what test the Court will apply by the questions asked. Admittedly, even if a justice asks about a particular test, she may not intend to use that test; but, I would suspect (and this is admittedly a hunch) justices are more inclined to ask about the standards they intend to write about.

Chief Justice Roberts and Justices Kennedy and Alito all cited "congruence and proportionality" as the standard.

CHIEF JUSTICE ROBERTS: Is the formula congruent and proportional today, or do you have this reverse engineering argument?

...​

To -- to the problem or -- or was the formula congruent and proportional to the remedy?

​Tr. at 45.

CHIEF JUSTICE ROBERTS: Well, we also said congruent and proportional.

Tr. ​at 56.

​

JUSTICE KENNEDY: Is that a methodology that in your view is appropriate under the test of congruence and -- and proportionality?

Tr. at 19.​

JUSTICE ALITO: But when Congress decided to reauthorize it in 2006, why wasn't it incumbent on Congress under the congruence and proportionality standard to make a new determination of coverage? . . .

But why -- why wasn't that required by the congruence and proportionality standards?

Tr. at 33-34.​

Justice Sotomayor suggested the standard might be irrelevant, and did ask about the Fifteenth Amendment.

JUSTICE SOTOMAYOR: And so the question becomes, why do we strike down a formula, as Justice Kagan said, which under any circumstance the record shows the remedy would be congruent, proportional, rational, whatever standard of review we apply, its application to Alabama would happen.

​Tr. at 6.

JUSTICE SOTOMAYOR: Would you tell me what you think is left of the rational means test in Katzenbach and City of Rome? Do you think the City of Boerne now controls both Fourteen -- the Fourteenth and the Fifteenth Amendment and how we look at any case that arises under them?

​Tr. at 27.

Justice Breyer repeatedly emphasized rational basis review.​

JUSTICE BREYER: And so the question I guess is, is it rational to pick out at least some of those States? And to go back to Justice Sotomayor's question, as long as it's rational in at least some instances directly to pick out those States, at least one or two of them, then doesn't the statute survive a facial challenge?

...​

That's the question of rationality.​

​Tr. at 12-13.

JUSTICE BREYER: Is that an irrational decision?​

Tr. at 17.​

JUSTICE BREYER: So it was rational when you continue.​

...​

I want to know what your response is as to whether we should -- if he's right -- if he's right that there is an ir rationality involved if you were writing it today in treating State A, which is not too discriminatorily worse than apparently Massachusetts or something.

Tr. at 43-44.​

JUSTICE BREYER: ​ Now the question is, is it rational to do that?

Tr. at 60.​

(Note that some of these address the "equal footing doctrine," a slightly different argument about whether Congress may treat some states differently than others.)​

​I should note one important fact: oral argument may (emphasis on "may") have illuminated what standard they intend to apply. But there is essentially no attempt to ask the advocates which standard should apply, or why a particular standard is preferred (except Justice Sotomayor's question about the Fifteenth Amendment). It is as if each justice has already determined the standard and is simply asking the advocates to apply that standard given the factual context.

That's certainly a useful exercise. But it does suggest that oral argument is not serving the clarifying purpose that one might aspire for it to perform.