Rule 23.Class actions

Rule 23(a) sets four prerequisites that must all be satisfied before anyone can sue or be sued as a class representative: the class must be so numerous that joining every member is impracticable; there must be questions of law or fact common to the class; the representative parties' claims or defenses must be typical of the class's claims or defenses; and the representative parties must adequately protect the interests of the class.

Rule 23(b) then requires one of three additional showings. Under (b)(1), separate actions by or against individual members would risk inconsistent adjudications that create incompatible standards of conduct for the opposing party, or would risk adjudications that, as a practical matter, dispose of or substantially impair the interests of class members not before the court. Under (b)(2), the opposing party has acted or refused to act on grounds generally applicable to the whole class, making final injunctive or corresponding declaratory relief appropriate for the class as a whole. Under (b)(3), common questions of law or fact predominate over questions affecting only individual members, and a class action is superior to other available methods for adjudicating the controversy — a finding the court bases on class members' interest in individually controlling their own litigation, the extent of any related litigation already under way, the desirability of concentrating the litigation in this forum, and the difficulties likely in managing a class action.

Rule 23(c) governs certification and notice. As soon as practicable after the action's commencement, the court must decide by order whether it will be maintained as a class action, and that order can be conditional and can be altered or amended before a decision on the merits. For a (b)(3) class specifically, the court must direct the best notice practicable to the class, including individual notice to members who can be identified through reasonable effort, telling each member of the right to request exclusion by a specified date, that the judgment will bind everyone who doesn't request exclusion, and that a member who stays in may enter an appearance through counsel. The judgment itself must describe the class members bound by it — for (b)(1) and (b)(2) classes, those the court finds to be members; for (b)(3) classes, those who received notice, didn't request exclusion, and were found to be members. The court can also certify a class action as to particular issues, or divide a class into subclasses treated as separate classes.

Rule 23(d) gives the court broad authority to manage a pending class action — controlling the course of proceedings, ordering notice for the protection of members or the fair conduct of the case, imposing conditions on representatives or intervenors, and requiring pleadings to be amended to drop allegations about representing absent persons. Rule 23(e) requires court approval before any class action is dismissed or compromised, along with notice to the class by mail, publication, or other means the court directs — except that a dismissal without prejudice to the class, or with prejudice to the named plaintiff only, can be ordered without notice if there's a showing that no compensation has passed, directly or indirectly, from any defendant to the plaintiff or the plaintiff's attorney, and that none has been promised.