The U.S. Supreme Court served up plenty of red meat for conservative commentators Monday: Not only did it rule 5-4 in favor of white firefighters in New Haven, Conn., who claimed discrimination in promotions practices, but in so doing, it reversed an appeals court panel that included Sonia Sotomayor, President Barack Obama’s nominee to replace retiring Justice David Souter.

By the time you read this editorial, you might have gotten an earful from cable TV talkers about how the court majority struck a mighty blow against “reverse” discrimination and repudiated Ms. Sotomayor, whose confirmation hearing begins in two weeks.

That is nonsense. The case of Ricci v. DeStefano is notable for what it doesn’t decide. The case was resolved on narrow facts. Constitutional issues were deferred until another day. The high court’s majority described its task as providing “guidance to employers” faced with “statutes and principals” that “point in different directions.”

To read the decision is to see the difficulties employers face when trying to craft systems that fairly measure qualifications for promotion and yield a diverse pool of candidates. These are difficulties the city of St. Louis know only too well.

St. Louis suffered a bitter rupture in race relations over fire department promotions in 2007. Sherman George, the city’s first African-American fire chief, was demoted after refusing an order from his boss, Mayor Francis Slay, to make promotions from a list of candidates selected by a test that Mr. George deemed flawed.

The list  included only a few black candidates, but the department’s tests and promotions process had been upheld by a federal judge after lengthy litigation.

The New Haven Fire Department case presented the same controversy from a different angle. In New Haven, it was the city that refused to go forward with a promotions list in which minority candidates were underrepresented, believing the process had been discriminatory.

A trial court held that the city was within its rights to scrap the promotional list and start over; the appeals court — including Ms. Sotomayor — agreed.

On Monday, the Supreme Court said that employers may void promotional lists that are a product of discriminatory promotional processes. And the court said employers do not have to seek a judicial ruling before acting. But, the court ruled, before promotions lists can be thrown out, there must be “a strong basis in evidence” that discrimination occurred. That standard requires more evidence than test results in which “higher-scoring candidates were white,” the court said.

Nothing about the court’s decision in New Haven case is sensational. The same cannot be said for promotions at fire departments — many of which have had long histories of racial exclusion.
Promotions processes are imprecise and imperfect, even at their very best. They are fraught with high emotion. Results almost invariably are challenged in court because people feel aggrieved.

True diversity is reached only when employers have a deep, continuing commitment to create opportunity for all talented people. That begins with recruitment and continues with training and mentoring. Candidates must be tested and selected fairly — not on rote memory, but on what it really takes to lead and succeed.

Ultimately, promoting diversity and reducing the heat of racial grievance depends on leadership, not lawsuits.