The U.S. Court of Appeals for the D.C. Circuit deepened a divide among circuits on Tuesday by holding that judges can’t deny class certification based only on a rule against “fail safe” class definitions, or when membership hinges on the case’s outcome on the merits.

Judges Patricia Millett and Harry Edwards and Chief Judge Sri Srinivasan sided with the minority of circuits in saying that courts weighing if a class should be certified shouldn’t ask if the definition is fail safe, but should instead tether their analysis to Rule 23, the federal rule for class action procedure, to weed out any problems.