Tips for Minding the “Ascertainability” of a Class

While most federal circuits agree that Rule 23 of the Federal Rules of Civil Procedure imposes an implied “ascertainability” requirement for class certification, a growing circuit split has emerged regarding the level of scrutiny courts should apply when determining if that requirement has been met. In this article, we discuss the circuit split and the impact of the Second Circuit’s recent decision on the issue in In re Petrobras Securities Litigation, and we provide guidance on what class action litigants may expect going forward.