When law professor Marin Levy clerked on the U.S. Court of Appeals for the Second Circuit, she learned for the first time about the court's "non-argument calendar" used for certain immigration cases. She wondered if other circuits had one too, but nobody had a definitive answer.

"It was a clerk of court at the time who summed this up by saying that what we don't know about the other courts far exceeds what we do [know]," Levy, who teaches at Duke University School of Law, said this week at a Supreme Court Historical Society event.