45 CFR 1617.2: Definitions.

(a) Class action means a lawsuit filed as, or otherwise declared by the court having jurisdiction over the case to be, a class action pursuant to Rule 23 of the Federal Rules of Civil Procedure or the comparable State statute or rule of civil procedure applicable in the court in which the action is filed.

(b)(1) Initiating or participating in any class action means any involvement at any stage of a class action prior to or after an order granting relief. “Involvement” includes acting as amicus curiae, co-counsel or otherwise providing representation relating to a class action.

(2) Initiating or participating in any class action does not include representation of an individual client seeking to withdraw from or opt out of a class or obtain the benefit of relief ordered by the court, or non-adversarial activities, including efforts to remain informed about, or to explain, clarify, educate or advise others about the terms of an order granting relief.