Also known as:Fed. R. Civ. P. 23 · Rule 23 · FRCP 23 · Federal Rules of Civil Procedure 23 · class action rule
Written by attorneys · grounded in primary & secondary sources — see below
A procedural rule promulgated under the Rules Enabling Act that establishes the prerequisites and procedures for maintaining a class action in federal court. The rule requires satisfaction of numerosity, commonality, typicality, and adequacy before certification and further mandates that one of the categories in subdivision (b) be met.
Sources & Authorities
How it applies
Common Examples
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Typicality and Adequacy in Pharmacy Rebates
Fairview Manufacturing and other independent pharmacies sued Meridian Labs in federal court under diversity jurisdiction seeking statutory interest on late rebate payments. The named plaintiff purchased the same rebate contracts and suffered identical delays as absent class members. The court found the representative's claims typical of the class and determined that the plaintiff and counsel would fairly protect class interests, allowing certification under Rule 23(b)(1)(A) to avoid inconsistent adjudications.
State Ban Displaced in Interest Claims
Francois Fortier filed a diversity class action against Foster Forge seeking statutory interest on delayed payments. A state statute barred class treatment for such interest-only claims. The federal court applied Rule 23 to assess certification because the rule regulates procedure without altering substantive rights to interest.
Select any source to read its text and confirm it supports the definition.
Cases
Statutes
Federal Rules
Hornbooks
Study Supplements
Federal Rule Controls Over State Procedure
Fatima Flores sued Fairfield Bank in federal court under diversity jurisdiction for delayed interest credits on deposits. A state statute prohibited class actions for interest disputes. The court applied Rule 23 to decide certification rather than the state restriction because the federal rule directly addressed the procedural question.
Hanna v. Plumer380 U.S. 460 (1965)
Class Certification Survives Mootness
Frederick Ferguson filed a class action challenging a state residency requirement for divorce. By the time the case reached the Supreme Court the named plaintiff's individual claim had become moot. The Court held that the class action could proceed because the controversy remained live for absent class members.
Sosna v. Iowa419 U.S. 393 (1975)
Fraud on the Market Supports Certification
Freya Freeman and other investors sued Basic Inc. alleging misleading public statements about a merger. Individual proof of reliance would have overwhelmed common issues. The Court applied a rebuttable presumption of reliance under the fraud-on-the-market theory to satisfy predominance and permit class treatment.
Basic Inc. v. Levinson485 U.S. [224], at 238 1988
Supplemental Jurisdiction Over Class Claims
Fabian Flynn and other customers sued Exxon Mobil in a diversity class action for overcharges. Some class members' claims fell below the jurisdictional amount. The Court held that supplemental jurisdiction extended to those claims once the named plaintiff's claim satisfied the amount-in-controversy requirement.
Exxon Mobil Corp. v. Allapattah Services, Inc.545 U.S. 546, 558–59 (2005)
Common questions
Frequently Asked
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Does Rule 23 govern class certification in a diversity action when a state statute bars class treatment for the same claims?+
Yes. When Rule 23 directly addresses whether an action may proceed as a class and is valid under the Rules Enabling Act, it controls over a conflicting state statute that merely limits the availability of the class device.
Supporting sources
What must a plaintiff show to satisfy the typicality and adequacy requirements under Rule 23(a)?+
The claims or defenses of the representative parties must be typical of the class, and the representatives must fairly and adequately protect class interests without conflicts that would impair vigorous prosecution.
Supporting sources
When may a federal court decline to exercise supplemental jurisdiction in a class action containing both federal and state claims?+
A court may decline supplemental jurisdiction when the state claims substantially predominate over the federal claims in scope, damages, or evidentiary demands, even if the class allegations share some common facts with the federal claim.
Supporting sources
Does Rule 23 permit certification when individual reliance issues would otherwise overwhelm common questions?+
Yes. Courts may apply a rebuttable presumption of reliance, such as under the fraud-on-the-market theory, to satisfy predominance when common questions of falsity, materiality, and scienter predominate over individualized reliance issues.
Supporting sources
380 U.S. 460 (1965)Conflict of Laws
…period when Cohen arose can appreciate the strong state policy reflected in the statute. I think it wholly legitimate to view Federal Rule 23 as not purporting to deal with the problem. But even had the FederalRules purported to do so, and in so doing provided a substantially less effective deterrent to strike suits, I think the…