Class Actions: Rule 23(a)

A class requires numerosity, commonality, typicality, and adequacy.

Related Parties & Joinder rules

• Compulsory CounterclaimsA counterclaim arising from the same transaction or occurrence must be raised or it is waived.
• Permissive CounterclaimsA permissive counterclaim does not arise from the same transaction and requires independent jurisdiction.
• CrossclaimsCrossclaims are always permissive and must arise from the same transaction or occurrence.
• Permissive Joinder of PartiesParties may join when claims arise from the same transaction or share a common question of law or fact.
• Compulsory JoinderA required party must be joined if feasible when complete relief cannot be accorded or existing parties face prejudice.
• Indispensable PartiesIf a required party cannot be joined, the court decides whether equity requires dismissal.
• Impleader (Third-Party Practice)A defendant may bring in a third party who may be liable for all or part of the plaintiff’s claim.
• InterpleaderInterpleader allows a stakeholder to force competing claimants to litigate entitlement to the same property or funds.

Part of Civil Procedure on Core Legal Rules — foundational MBE-tested principles with primary-source citations.