The basic concept which lies at the heart of my point about Congress, courts and the Fourteenth Amendment is indeterminacy. Consider as examples some commonplace legal principles: fairness, reasonableness, and proprtionality. These norms are all indeterminate because more than one concrete norm for implementing them is available. Thus, “fair” notice in beginning a suit against someone who has moved without leaving a forwarding address may be satisfied by mailing the complaint to his last known address, delivering the complaint to the nearest living relative, newspaper notice, or some combination of these. Each is more or less “fair.” Because the law has to be concrete in such circumstances, the competent authority (usually, the legislature) has to make a choice among such reasonable options. Once that choice is made, there is an end to it — the way to commence a suit against an absent defendant is settled.
“Equality” works this way too. Let’s suppose that in around 1868 reasonable people reasonably disagreed about whether genuinely comparable school facilities and faculty resources (and the like) constituted “equal educational opportunity” for blacks and whites, even if the schools were segregated. If this were the state of opinion, a court applying section one of the Fourteenth Amendment to a state with such schools might well be obliged to say: these schools do not violate the EPC; the state has adopted a reasonable view of what equality entails (even, the court might add parenthetically, if the choice is not what I — the judge — consider to be the best one). If this were the state of opinion, however, Congress could decide that segregated schools, though not inconsistent with the EPC, were not nearly as good a way to enforce the equal protection of the laws as would be integrated schools. Congress could then legislate against segregated schools, exercising a power to make a general principle concrete, in roughly the way a legislature might settle the best, or most fair, way to give notice of a suit.