Jones v. Harris Associates reached the Supreme Court after a showdown between two of the most well known judges on the 7th Circuit and, indeed, the whole country: Chief Judge Frank Easterbrook and former Chief Judge Richard Posner. Both are closely associated with the University of Chicago Program in Law and Economics and have taught at the university’s law school.

Posner delivered his opposition to Easterbrook’s Jones opinion as a dissent in the circuit’s decision not to hear the case en banc. It’s an unusual venue for such a high-impact opinion, says John Baker, of counsel at Stradley Ronon Stevens & Young.

“Judge Posner’s opinion was thoroughly researched,” he says. “Something you would not really expect from a mere dissent for a rehearing en banc.”

The circuit split caused by both judges’ well-thought out writing set the stage for the Supreme Court’s resolution.