You’re staring at an MBE question with five parties, three claims, and a class of 200 plaintiffs. Your brain freezes. Can these people even sue together? Joinder questions on the MBE aren’t just testing whether you know the rules—they’re testing whether you can apply Rules 19, 20, and 23 under time pressure without second-guessing yourself.
Let’s fix that.
Why Joinder and Class Actions Trip Up Bar Examinees
Civil Procedure joinder rules feel like a logic puzzle wrapped in procedural requirements. The MBE loves testing these concepts because they force you to juggle multiple issues at once: subject matter jurisdiction, personal jurisdiction, whether claims arise from the same transaction, and whether parties are required or merely permitted to join.
The biggest mistake? Treating all joinder rules as interchangeable. Rule 19 (compulsory joinder) asks whether a party must be joined. Rule 20 (permissive joinder) asks whether parties may join. Rule 23 (class actions) asks whether numerous parties can be represented by a few. Each has distinct requirements, and the MBE will punish you for conflating them.
Here’s what you need to memorize cold.
Rule 20: Permissive Joinder of Parties
Rule 20 governs when multiple plaintiffs can sue together or when a plaintiff can sue multiple defendants in a single action. This is “permissive” because no one is required to join—it’s allowed if two requirements are met.
The Two-Part Test for Permissive Joinder:
- Same transaction or occurrence: The claims must arise out of the same transaction, occurrence, or series of transactions or occurrences.
- Common question of law or fact: There must be at least one question of law or fact common to all parties.
Both prongs must be satisfied. If the claims arise from completely separate events, joinder is improper even if they involve similar legal issues.
MBE Hypothetical:
Plaintiff A and Plaintiff B were injured in separate car accidents—one in January, one in March—both caused by defective brakes manufactured by Defendant Corporation. Can they join as co-plaintiffs under Rule 20?
No. Even though both claims involve the same legal theory (products liability) and the same defendant, the accidents are separate occurrences. There’s no single transaction linking them. Each plaintiff must sue separately unless they can satisfy the same-transaction prong.
Now change the facts: Plaintiff A and Plaintiff B were passengers in the same car when the brakes failed, causing a single accident that injured both. Can they join?
Yes. Same transaction (one accident), common question of fact (were the brakes defective?). Rule 20 is satisfied.
Watch for the Jurisdiction Trap:
Even if Rule 20 permits joinder, you still need an independent basis for subject matter jurisdiction. If the case is in federal court based on diversity jurisdiction, adding a plaintiff from the same state as the defendant destroys complete diversity. The MBE will test whether you remember that permissive joinder doesn’t cure jurisdictional defects.
Rule 19: Compulsory Joinder (Required Parties)
Rule 19 deals with parties who should be joined if possible, and if they can’t be joined, whether the case can proceed without them. This rule has a three-step analysis that the bar exam loves.
Step One: Is the Absentee a Required Party Under Rule 19(a)?
A person is required to be joined if feasible when:
- Complete relief cannot be accorded among existing parties in the person’s absence, OR
- The person claims an interest in the action and disposing of the case in their absence would either:
- Impair their ability to protect that interest, OR
- Leave existing parties subject to a substantial risk of multiple or inconsistent obligations.
If the absentee doesn’t fall into one of these categories, they’re not required. End of analysis.
Step Two: Is Joinder Feasible?
If the person is required under Rule 19(a), the court must join them if feasible. Joinder is feasible unless:
- It would destroy subject matter jurisdiction (e.g., destroy complete diversity), OR
- The court lacks personal jurisdiction over the absentee, OR
- Venue would be improper.
If joinder is feasible, the court orders the absentee joined. If not, move to step three.
Step Three: Can the Case Proceed Without the Absentee?
Under Rule 19(b), if the required party cannot be joined, the court decides whether to proceed without them or dismiss the action. The court considers:
- The extent of prejudice to the absentee or existing parties
- Whether protective measures can lessen prejudice
- Whether a judgment without the absentee would be adequate
- Whether the plaintiff would have an adequate remedy if the action is dismissed
If the absentee is deemed indispensable, the case must be dismissed. This is rare but appears on the MBE.
MBE Hypothetical:
Plaintiff sues Defendant over ownership of a parcel of land. A third party, Neighbor, also claims an ownership interest in the same land. Is Neighbor a required party?
Yes. Neighbor has a direct interest in the subject matter, and resolving the case without Neighbor could impair Neighbor’s ability to protect that interest (they wouldn’t be bound by the judgment but also couldn’t relitigate the issue). If Neighbor can’t be joined because it would destroy diversity, the court must determine under Rule 19(b) whether Neighbor is indispensable. If so, the case is dismissed.
Rule 23: Class Actions on the Bar Exam
Class actions allow one or more plaintiffs to sue on behalf of a larger group. The MBE tests whether a proposed class satisfies the prerequisites and fits within one of the recognized categories.
Four Prerequisites for Any Class Action (Rule 23(a)):
Every class action must satisfy all four:
- Numerosity: The class is so numerous that joinder of all members is impracticable. (No magic number, but typically 40+ members.)
- Commonality: There are questions of law or fact common to the class.
- Typicality: The representative parties’ claims or defenses are typical of the class.
- Adequacy of Representation: The representative parties will fairly and adequately protect the interests of the class.
If any of these four is missing, the class cannot be certified. Period.
Rule 23(b) Categories:
Even if all four prerequisites are met, the action must also fit into one of three categories under Rule 23(b):
- 23(b)(1): Prosecuting separate actions would create a risk of inconsistent adjudications or impair the interests of absent class members. (Rare on the MBE.)
- 23(b)(2): The defendant has acted or refused to act on grounds generally applicable to the class, making injunctive or declaratory relief appropriate. (Think civil rights cases seeking systemic change.)
- 23(b)(3): Common questions of law or fact predominate over individual questions, and a class action is superior to other methods of adjudication. This is the most common category and requires notice to all class members, who have the right to opt out.
MBE Hypothetical:
Two hundred consumers purchased the same defective toaster from Defendant Corporation. Each consumer suffered minor burns and property damage ranging from $50 to $500. Plaintiff files a class action in federal court under diversity jurisdiction, seeking damages on behalf of all purchasers. Can the class be certified?
Analysis: Numerosity is clearly satisfied (200 members). Commonality exists (was the toaster defective?). Typicality and adequacy depend on whether Plaintiff’s claim is representative and whether Plaintiff can adequately represent the class—assume yes for the hypo. The action fits Rule 23(b)(3) because common questions (defect, causation) predominate, and a class action is superior given the small individual damages.
The Class Action Fairness Act (CAFA) Wrinkle:
For diversity jurisdiction, the normal rule requires complete diversity and $75,000 in controversy. But under CAFA, a class action needs only minimal diversity (at least one plaintiff from a different state than one defendant) and an aggregate amount in controversy exceeding $5 million. The MBE occasionally tests whether you know this exception to the complete diversity rule.
In the toaster hypo above, even if the named plaintiff is from the same state as the defendant, minimal diversity exists if any class member is diverse. And 200 claims of $50–$500 each easily exceed $5 million in the aggregate.
How to Approach Joinder Questions on the MBE
When you see a multi-party question, follow this checklist:
- Identify the rule in play: Is this about whether parties can join (Rule 20), must join (Rule 19), or whether a class action is proper (Rule 23)?
- Apply the elements mechanically: Don’t skip steps. For Rule 20, check same transaction and common question. For Rule 19, walk through all three steps.
- Check jurisdiction separately: Permissive joinder doesn’t create jurisdiction. If the question involves diversity, confirm complete diversity still exists (or CAFA applies for class actions).
- Watch for red herrings: The MBE will include irrelevant facts to distract you. Stay focused on the elements.
The examiners know most students mix up Rules 19 and 20, or forget that Rule 23(a) has four prerequisites, not three. Drill these distinctions until they’re automatic.
Memorize These Takeaways
Rule 20 (Permissive Joinder):
- Same transaction or occurrence + common question of law or fact
- Doesn’t cure jurisdictional defects
Rule 19 (Compulsory Joinder):
- Step 1: Is the absentee required? (Complete relief impossible, or absentee’s interest would be impaired)
- Step 2: Is joinder feasible? (Jurisdiction, venue, personal jurisdiction)
- Step 3: If not feasible, is the absentee indispensable? (If yes, dismiss)
Rule 23 (Class Actions):
- Four prerequisites: numerosity, commonality, typicality, adequacy
- Must fit a 23(b) category (usually 23(b)(3) for damages)
- CAFA: minimal diversity + $5 million for class actions
If you want all 99 Civil Procedure rules organized for active recall—including the full joinder framework, supplemental jurisdiction limits on joined parties, and every other topic the MBE tests—FlashTables covers them in a two-column format designed for exactly this kind of rapid review. No fluff, just the elements you need to apply under pressure.
Now go drill some practice questions. You’ve got this.