Concept
Diversity Limits: § 1367(b)
Supplemental jurisdiction
Diversity Limits: § 1367(b)
Subsection (a) is broad, and subsection (b) takes part of that breadth back, but only in one kind of case. The trigger is in the opening words: the limit applies in a civil action "of which the district courts have original jurisdiction founded solely on section 1332."1 When the anchor claim arises under federal law, or when federal question jurisdiction stands beside diversity, the action is not founded solely on diversity and subsection (b) never comes into play. A plaintiff who sues under Title VII and adds a state-law wrongful-discharge claim, for example, can add further related claims and parties without meeting (b), because the original jurisdiction does not rest solely on § 1332.2 Only when diversity is the single support for the anchor claim does the court have to ask what (b) forbids.
The reason for the limit lies in the complete diversity rule, which requires that no plaintiff share citizenship with any defendant. That rule keeps diversity jurisdiction confined to cases where the parties are on opposite sides of a state line, and (a) alone would let a plaintiff slip around it. Imagine a Kansas patient who wants to sue four doctors for malpractice in the same heart surgery, one from Missouri and three from Kansas. Suing all four at once would destroy complete diversity. But the patient could sue only the Missouri doctor, which satisfies § 1332, and then join the three Kansas doctors under Rule 20. Their claims share a common nucleus of fact with the first, so (a) would appear to cover them, and the complete diversity rule would disappear.3 Subsection (b) closes that gap. The House Report described its aim as preventing plaintiffs from evading § 1332 by naming at first only the defendants whose joinder satisfies it and later adding claims against others brought in on a supplemental basis.4 The bar applies when supplemental jurisdiction "would be inconsistent with the jurisdictional requirements of section 1332," and those requirements are complete diversity and the amount in controversy.5
The statute names two groups of barred claims, and the next two sections take them in turn. The first group is claims against persons joined as parties, and the second is claims by persons seeking to enter the case as plaintiffs.
Claims Against Joined Parties
The first bar reaches "claims by plaintiffs against persons made parties under Rule 14, 19, 20, or 24."7 Two features of that phrase control the analysis. The claimant must be a plaintiff, and the target must be someone who entered the case through impleader, compulsory joinder, permissive joinder, or intervention. The heart-surgery hypothetical above is the Rule 20 version: the patient's claims against the three Kansas doctors are claims by a plaintiff against persons made parties under Rule 20, so supplemental jurisdiction is unavailable and each claim needs an independent basis.8
The paradigm is Owen Equipment & Erection Co. v. Kroger, in which the Supreme Court held that ancillary jurisdiction did not extend to a plaintiff's claim against a nondiverse party whom the defendant had impleaded under Rule 14.9 The plaintiff's claim against the impleaded party arose from the same events as the main claim, so it satisfied the common-nucleus standard. Relatedness was therefore not the problem. The problem was that allowing the claim would let the plaintiff acquire, through the defendant's act of impleading, a nondiverse opponent whom the plaintiff could not have sued directly. Subsection (b) is the codification of that rationale, and the House Report said so.10
The bar is aimed at plaintiffs because only a plaintiff chooses the forum and the parties. A plaintiff who wants to evade complete diversity can do so by controlling whom to sue first and whom to add later. A defendant, by contrast, was "hauled into court against his will" and has no such choice, so Kroger treated a defendant's reactive claims as presenting no comparable risk of manipulation.11 That is why a defendant's claims are generally permitted and a plaintiff's are restricted, a pattern sometimes summarized as the defensive-posture rule.
A matched pair shows which fact decides the outcome. Suppose Browning, a New York citizen, sues Blake, an Ohio citizen, for $100,000 over a car accident. Blake impleads Wordsworth, also an Ohio citizen, claiming contribution. Blake and Wordsworth share citizenship, so the third-party claim has no independent basis, but it is a claim by a defending party and (b) does not mention it, so supplemental jurisdiction supports it.12 If Browning then asserts his own claim directly against Wordsworth, the claim comes from a plaintiff against a Rule 14 party. Wordsworth is not diverse from Browning's co-party, but more to the point Browning's claim is barred unless it independently satisfies § 1332, which it does only if Wordsworth is diverse from Browning and the claim exceeds $75,000.13
The text produces one result that is hard to defend. When Blake impleads Wordsworth and Wordsworth asserts a claim against Browning, Browning must assert any compulsory counterclaim arising from the accident, and that counterclaim would be against a person made a party under Rule 14. Read literally, (b) bars it, even though hearing it would save effort. At least one court has applied the language as written while saying it wished it could do otherwise.14 The exam answer follows the text.
Plaintiffs Joining or Intervening
The second bar looks at persons who want to enter the case on the plaintiff's side. Supplemental jurisdiction is unavailable for "claims by persons proposed to be joined as plaintiffs under Rule 19" and for claims by persons "seeking to intervene as plaintiffs under Rule 24."16 The abuse being blocked is the same as before, approached from the other side. Suppose a Kansas plaintiff sues a Missouri defendant, and two Missouri citizens then seek to intervene as plaintiffs with similar claims. The Missouri intervenors would be suing a fellow citizen, so their claims could never have been brought originally, and (b) refuses to let them ride the first plaintiff's diversity claim into court.17
Intervention under Rule 24 is barred whether it is of right or permissive. Before 1990 an intervenor of right could often use ancillary jurisdiction while a permissive intervenor could not, but the statute lists Rule 24 plaintiffs as a single category and no longer draws that line.18 So a would-be plaintiff who shares citizenship with the defendant cannot enter a diversity-only case by intervening, however closely the claim tracks the main one, unless the claim independently satisfies § 1332 or the person's claim raises a federal question.19
The list has an odd gap. It bars plaintiffs proposed under Rule 19 and Rule 24 but does not mention plaintiffs joined permissively under Rule 20, even though a Rule 20 plaintiff presents the same risk. The omission looks like a drafting error, and the Supreme Court addressed it in Exxon Mobil Corp. v. Allapattah Services, Inc., holding that a plaintiff added under Rule 20 may rely on supplemental jurisdiction without meeting the amount in controversy, so long as the addition does not destroy complete diversity.20 The Court's reasoning is taken up in its own section, but the practical consequence belongs here: the statute's text, not the bar's purpose, determines which plaintiffs are shut out.
The point can be shown with two plaintiffs. Suppose a Michigan citizen sues an Ohio citizen for $100,000 over a car crash, and a second Michigan plaintiff joins under Rule 20 with a $50,000 claim from the same crash. The second claim is not barred, because Rule 20 plaintiffs are not on the list and diversity remains complete.21 Change the second plaintiff to an Ohio citizen, and the claim fails for a different reason: the added plaintiff shares citizenship with the defendant, so complete diversity is gone and no original jurisdiction remains for the claim.22
What Subsection (b) Does Not Bar
Knowing the limits of the bar matters as much as knowing what it forbids, and three boundaries do most of the work. The first is the trigger already discussed: (b) governs only when original jurisdiction is founded solely on § 1332. If a federal-question claim anchors the case, a plaintiff may use (a) to add related state-law claims against new defendants, even nondiverse ones, and (b) never applies.24
The second boundary is that (b) restricts only certain plaintiff-side claims. Compulsory counterclaims, crossclaims between defendants, and third-party claims by a defendant against an impleaded party do not appear on the list, so they remain within supplemental jurisdiction if they satisfy (a).25 A defendant may therefore assert a compulsory counterclaim against a new, nondiverse party joined under Rule 13(h), even though a plaintiff could not have sued that party in the first place.26
The third boundary is that (b) limits supplemental jurisdiction and does not touch diversity jurisdiction that stands on its own. The statute's closing clause bars supplemental jurisdiction only where it would be inconsistent with § 1332, so a claim that independently satisfies § 1332 needs no supplement.27 A California plaintiff who sues one defendant and then joins an Oregon defendant cannot rely on supplemental jurisdiction for the second claim, but if the claim is for more than $75,000 and the Oregon defendant is diverse from every plaintiff, ordinary diversity jurisdiction supports the joinder.28 If instead the Oregon claim were for $20,000, it would fail, because the amount requirement is also part of what (b) protects.
Claims Against Joined Parties
The first group of claims that subsection (b) removes from supplemental jurisdiction is defined by who asserts the claim and by how the target entered the case. In a civil action whose original jurisdiction rests solely on diversity, the district court has no supplemental jurisdiction over "claims by plaintiffs against persons made parties under Rule 14, 19, 20, or 24" when exercising it would be inconsistent with the requirements of § 1332.30 Three features of that sentence control the analysis. The claimant must be a plaintiff. The target must have become a party through impleader, compulsory joinder, permissive joinder, or intervention. And the bar operates only to the extent that hearing the claim would defeat complete diversity or the amount in controversy.
The reason for aiming the bar at plaintiffs lies in who controls the shape of the lawsuit. A plaintiff chooses the forum and decides whom to sue, so a plaintiff can structure the case to satisfy § 1332 at the outset. Suppose a Kansas patient wants to sue four doctors over one heart operation, one from Missouri and three from Kansas. Suing all four together would destroy complete diversity, but the patient could sue only the Missouri doctor, which satisfies § 1332, and then join the Kansas doctors under Rule 20. Because all four claims grow from the same operation, subsection (a) would reach them, and the complete diversity rule could be avoided simply by choosing the order in which to name the defendants.31 Subsection (b) closes that route by denying supplemental jurisdiction over the patient's claims against the Rule 20 defendants, so each of those claims must stand on its own diversity and amount.32
The same logic governs the paradigm case, Owen Equipment & Erection Co. v. Kroger, in which a plaintiff asserted a claim against a third-party defendant whom the original defendant had impleaded under Rule 14. That claim arose from the same facts as the main claim, so it satisfied the Gibbs common-nucleus test, yet the Court held that there was no jurisdiction over it in a diversity case, and Congress took the same position when it wrote subsection (b).33 Relatedness was therefore not the problem. The danger was that the defendant's decision to implead would hand the plaintiff an opponent the plaintiff could not have sued directly without destroying diversity. The example is easy to state: P sues D, D impleads X, and P and X share citizenship, so P's claim against X must be dismissed.34 The same result follows when a person is joined under Rule 19(a), because neither a plaintiff's claim against that person nor that person's claim is within supplemental jurisdiction in a diversity-only case.35
The bar is lifted when the claimant is a defendant. A defendant did not choose the forum and was brought into court against his will, so a defendant's reactive claims carry no comparable risk of manipulating diversity. Imagine that Dana, an Illinois citizen, sues Everett, an Indiana citizen, for $200,000 after a collision, and Everett impleads Farid, also an Indiana citizen, seeking contribution. Everett and Farid share citizenship, so the impleader claim has no independent basis, and it is measured as a separate claim, which means that Farid's diversity from Dana does not help. Even so, the claim is a defendant's claim, subsection (b) does not list it, and supplemental jurisdiction supports it because it arises from the same accident.36 The same is true of a claim by the third-party defendant against the plaintiff, even though the amount requirement may not be met, because the claimant is a defendant and not a plaintiff.37
Now reverse the direction of the claim. If Dana asserts her own claim against Farid, she is a plaintiff suing a person made a party under Rule 14, and the bar applies. The claim survives only if it independently satisfies § 1332, since a claim with its own diversity jurisdiction never needs supplemental jurisdiction. Farid is an Indiana citizen and Dana is from Illinois, so diversity is present, and the claim is heard if it exceeds $75,000. If Dana's claim against Farid is for $60,000, the court has no jurisdiction over it.38 Had Farid also been an Illinois citizen, the claim would fail for want of diversity, whatever its amount. The same impleaded party and the same facts thus produce opposite outcomes depending on who asserts the claim, which is the pattern often summarized as the requirement of a defensive posture.39
Plaintiffs Joining or Intervening
The second group of claims removed from supplemental jurisdiction is defined by who is trying to enter the case on the plaintiff's side. In a civil action whose original jurisdiction rests solely on diversity, the district courts have no supplemental jurisdiction over claims by persons proposed to be joined as plaintiffs under Rule 19, or by persons seeking to intervene as plaintiffs under Rule 24, when exercising it would be inconsistent with § 1332.41 The first bar, discussed above, looks at plaintiffs who sue newly added defendants. This one looks at newcomers who want to become plaintiffs, and it exists for the same reason: the complete diversity rule would otherwise be easy to avoid.
The mechanism is easiest to see in a concrete case. Suppose a Kansas citizen sues a Missouri defendant for $100,000 in defamation, and two Missouri citizens with similar defamation claims then ask to intervene as plaintiffs. The Kansas plaintiff alone satisfies § 1332, so the case is properly in federal court. The two Missouri claims share a common nucleus of operative fact with the first claim, so subsection (a) would reach them if it stood alone. But the Missouri intervenors could never have sued their fellow Missouri citizen in federal court at the outset, and without subsection (b) they could simply wait for a diverse plaintiff to open the door and then walk through it.42 Subsection (b) shuts that door, so each intervenor's claim must stand on its own jurisdictional footing.
The bar applies whether intervention is of right or permissive. Before the 1990 statute, courts generally demanded an independent jurisdictional basis for permissive intervention under Rule 24(b) but not for intervention of right under Rule 24(a), because the intervenor of right was thought to have a stronger claim to be heard.43 The statute's text lists "Rule 24" as a single category, and the line between the two kinds of intervention no longer matters for jurisdiction.44 The same treatment extends to a person who should be joined as a plaintiff under Rule 19(a). In both settings the would-be plaintiff cannot enter a diversity-only case unless the claim raises a federal question or independently satisfies § 1332, meaning the claimant is diverse from every defendant and the claim exceeds $75,000.45
The bar does not exclude every intervenor. Return to the Kansas plaintiff and the Missouri defendant, and suppose a third person from Texas seeks to intervene as a plaintiff with a $90,000 claim against the same defendant. That claim needs no supplement, because it satisfies § 1332 by itself, and subsection (b) restricts only supplemental jurisdiction, not diversity jurisdiction that stands on its own.46 The same facts with a Missouri intervenor produce the opposite result, so the intervenor's citizenship is the fact that decides the outcome.
The list has an odd gap that the next major section takes up. Rule 19 plaintiffs and Rule 24 plaintiffs are barred, but plaintiffs joined permissively under Rule 20 are not mentioned, even though they present the same risk. The omission looks like a drafting error, and the Supreme Court addressed it in Exxon Mobil Corp. v. Allapattah Services, Inc., holding that a Rule 20 plaintiff may rely on supplemental jurisdiction without meeting the amount in controversy so long as the joinder does not destroy complete diversity.47 For now, the point to carry forward is that the text of subsection (b) sets the list, and an exam answer reads the list as written.
What Subsection (b) Does Not Bar
Subsection (b) is easy to over-read, because its list of forbidden claims is vivid and the lesson of the complete diversity rule is fresh. The provision is narrower than it first appears, and its limits come from three features of its text: the trigger that switches it on, the list of claims it reaches, and the closing clause that preserves ordinary diversity jurisdiction. Each limit has a reason rooted in the purpose of the bar, which is to stop a plaintiff from using the liberal joinder rules to evade the complete diversity requirement of § 1332.49 Where that danger is absent, the broad grant in subsection (a) operates untouched.
The first limit is the trigger. Subsection (b) applies only in a civil action whose original jurisdiction is "founded solely on section 1332."50 If any claim in the case rests on a federal question, the original jurisdiction is not founded solely on diversity, and subsection (b) never comes into play. The same is true when a case combines a federal claim with a diversity claim, because the original claims then are not based exclusively on § 1332.51 In that setting, a federal-question claim at the center of the case supports supplemental jurisdiction over any related claim, including claims that add new defendants or new plaintiffs.52
A concrete pair of cases shows how the trigger decides the result. Suppose Marta, an Ohio citizen, sues an Ohio lender in federal court under the federal Truth in Lending statute, and then adds the Ohio car dealer as a defendant on a related Ohio-law claim worth $20,000. There is no diversity and the amount in controversy is too small, yet the state claim against the dealer is heard, because it arises from the same transaction as the federal claim and subsection (b) does not apply to a case anchored in federal law.53 Now strip out the federal claim and let Marta sue the lender on state law alone, relying on diversity. If she then adds the nondiverse dealer, subsection (b) applies, and the same added claim is barred. The related facts are identical in both versions. What changed is the foundation of the original jurisdiction, and that foundation controls whether the bar is switched on.
The second limit is that subsection (b) lists only certain claims, and every listed claim is asserted by a plaintiff or by someone trying to become one. Claims by defendants do not appear. A compulsory counterclaim, a crossclaim by one defendant against another, an impleader claim by a defendant against a third-party defendant, and a claim by the third-party defendant against anyone else all remain available if they satisfy subsection (a).54 A crossclaim, for instance, must arise from the same transaction as the main claim, so it is part of the same constitutional case, and because a defendant asserts it, subsection (b) leaves it alone.55 The same reasoning lets a defendant bring a nondiverse outsider into a compulsory counterclaim under Rule 13(h). Imagine a New York plaintiff who sues a New Jersey defendant for $60,000 in diversity. The defendant counterclaims for injuries that arose in the same episode, and adds Y, another New Jersey citizen, as a counterclaim defendant. Neither the shared New Jersey citizenship nor the small amount matters, because supplemental jurisdiction covers the claim.56
The reason for the asymmetry follows from who controls the lawsuit. A plaintiff chooses the court and decides whom to sue, so a plaintiff who could manipulate jurisdiction by sequencing claims is the actor the complete diversity rule needs to restrain. A defendant has been brought into the forum involuntarily and needs a chance to resolve closely related claims in the same proceeding, and a defendant's reactive claims give no comparable opportunity to engineer diversity. That difference is often compressed into a rule of thumb about posture: in a diversity-only case, supplemental jurisdiction helps those in a defensive position, which means defendants and third-party defendants, and does not help plaintiffs who add claims.57 The rule of thumb is a shortcut and does not replace the text. It works because the text of the statute lists the same plaintiff-side claims, and the third-party plaintiff and third-party defendant stand in the defendant's shoes.
The third limit comes from the closing clause. The bar applies only when supplemental jurisdiction "would be inconsistent with the jurisdictional requirements of section 1332."58 A claim that satisfies § 1332 by its own strength needs no supplement, so there is nothing for subsection (b) to take away. A California plaintiff in a diversity case who joins a new Oregon defendant cannot rely on supplemental jurisdiction for the claim against that defendant, but if the claim exceeds $75,000, the claim stands on ordinary diversity jurisdiction and proceeds.59 The same new defendant sued for $20,000 produces the opposite result, because the claim then has neither a supplemental nor an independent basis. The difference between the two outcomes is the amount, and it shows that (b) leaves the requirements of § 1332 fully in force for plaintiffs' added claims and does not replace them.
The sequence matters because the steps filter in a fixed order. Steps one and three each end the inquiry early in the claimant's favor, step four narrows the field to the plaintiff-side claims the statute names, and step five rescues those claims that never needed supplemental jurisdiction.