How do you count the people in Congressional districts?

A savvy registered voter in New York brought a lawsuit challenging the constitutionality of the congressional districts in this state. His argument is that while the constitution requires that each congressional district have the same number of people, the districts are illegal because they do not have have the same number of people eligible to vote.

The case is Kalson v. Paterson, decided on September 9. As the Court of Appeals notes, "congressional districts within a state must have the same population." That way, the congressman in Manhattan wields the same power as the congresswoman in Buffalo (at least in theory, anyway). But, Judge Calabresi points out,

The Supreme Court . . . has never precisely defined what is the relevant “population” for the purposes of apportioning congressional representation. And, behind this case there lies a theoretically difficult question, whether congressional districts must be of the same total population — the number of residents within each district — or some different population that represents the number of votes cast in each district. Put differently, this is a choice between two conceptions of democratic equality, "electoral equality” and “equal representation.”

In other words, how do we classify "population": by the number of people in the congressional district, or by the number of people who are eligible to vote? The question is important, because the plaintiffs says that, since other districts have fewer registered voters, his vote actually has less weight than those cast in other districts.

A judge in the district court dismissed the case, hence this appeal. The Court of Appeals deems this an interesting case, and it is, although the Supreme Court hinted in 1969 that the plaintiff is probably wrong. At best, the Second Circuit says, this case is not obviously frivolous. Before the Court can deal with this issue, though, it has to resolve a procedural problem: cases like this should be handled by three district court judges before they reach the Court of Appeals, unlike 99 percent of all other cases which go before one district court judge. No one asked for a three-judge panel, and that normally prevents the Second Circuit from even hearing the case if, and only if, the case has a substantial basis in law. Put another way, if the case is weak, it does not matter that no three-judge panel was convened.

So the Second Circuit is tasked with determining whether this case is substantial or not, as opposed to determining whether the plaintiff should win the case and on what legal basis. The Court says this case is not substantial, however, excusing the lack of a three-judge panel in the district court and ruling against the plaintiff on the merits. Judge Calabresi reaches this conclusion because "Plaintiff does not assert that voting age is the best available proxy for actually equal voting power." The Court adds,

Even assuming, arguendo, that districts must be apportioned to create, or even just to approximate an equal number of voters, it does not follow at all that districts should be apportioned by voting-age population. Were it true, as Plaintiff argues, that [the Constitution] creates an individual right to an equally weighted vote, that right is not vindicated by having districts of equal voting-age population. Many persons of voting age cannot vote, such as felons, ex-felons, and noncitizens, and many eligible voters choose not to vote.