In 2012, the Fifth Circuit became the first circuit court to explicitly reject an argument that a fail-safe class—a class defined in terms of the defendant’s liability—was barred from class certification under Federal Rule of Civil Procedure 23. Drawing on previous cases in which it had rejected challenges that class definitions were circular, the Fifth Circuit in In re Rodriguez outright disclaimed a prohibition against fail-safe classes. This decision diverged from the Sixth and Seventh Circuits’ proscription against certifying fail-safe classes, creating a split among the circuits.

This Note explores this circuit split and argues that fail-safe classes must be proscribed because they allow class members to escape the bar of res judicata. This Note concludes that characterizing a class as fail-safe should provide independent justification for denying class certification.