Supplemental Jurisdiction

Supplemental Jurisdiction

Supplemental jurisdiction is the doctrine that allows a federal court to hear additional claims that do not independently satisfy the requirements for federal subject-matter jurisdiction, when those claims are sufficiently related to a claim over which the court already has original jurisdiction. The central statutory provision is 28 U.S.C. § 1367, which generally permits federal courts to hear claims forming part of the same constitutional “case or controversy” as claims already within the court’s original jurisdiction. Cornell Law School’s text of 28 U.S.C. § 1367 provides the statutory framework.

Supplemental jurisdiction is important because a single lawsuit frequently contains several legal claims arising from the same events. One claim may arise under federal law while another arises under state law. If federal courts could hear only claims independently satisfying federal jurisdictional requirements, many disputes would have to be divided between federal and state courts. Supplemental jurisdiction allows related claims to be handled together, while preserving important limitations based on federalism, statutory jurisdictional requirements, and judicial discretion.

The doctrine therefore occupies a middle ground: a federal court must have original jurisdiction over at least one claim, the additional claims must be sufficiently related, and statutory limitations or discretionary considerations may still prevent the court from hearing them.

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1. What Is Supplemental Jurisdiction?

Supplemental jurisdiction is federal judicial authority over claims that, standing alone, would not necessarily fall within the court’s original subject-matter jurisdiction but are sufficiently connected to claims that do.

For example, suppose a plaintiff brings a federal civil-rights claim against a city and also brings a state-law claim arising from exactly the same encounter.

The federal civil-rights claim may provide federal-question jurisdiction under 28 U.S.C. § 1331.

The state-law claim may not independently present a federal question, and the parties may not be diverse.

Nevertheless, the federal court may be able to hear both claims because they arise from the same underlying events.

That is the basic idea behind supplemental jurisdiction.

The doctrine is not an independent replacement for subject-matter jurisdiction. Instead, it supplements an existing basis of federal jurisdiction.

A useful way to conceptualize the relationship is:

Original jurisdiction gets the case into federal court. Supplemental jurisdiction may allow the court to keep related claims together.

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2. Why Does Supplemental Jurisdiction Exist?

The doctrine reflects practical and constitutional considerations.

A single factual dispute can generate several legal claims under different sources of law.

Consider a workplace dispute in which an employee alleges:

• discrimination under federal law;
• violation of a state employment statute;
• state-law wrongful termination;
• state-law defamation; and
• intentional infliction of emotional distress.

If the federal claim and the state claims arise from substantially the same events, forcing the parties to litigate them in separate courts could produce unnecessary duplication.

The parties might have to:

• present the same witnesses twice;
• introduce the same documents in two proceedings;
• prove overlapping facts before different judges;
• litigate similar factual disputes separately; and
• potentially obtain inconsistent findings.

Supplemental jurisdiction promotes judicial economy, convenience, and fairness by allowing sufficiently related claims to proceed together.

But efficiency is not the only concern.

Federal courts are courts of limited jurisdiction. The Constitution and Congress place boundaries around their authority. Supplemental jurisdiction therefore cannot simply be justified by saying that hearing all claims together would be convenient.

Congress has established a specific statutory framework in § 1367.

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3. The Statutory Foundation: 28 U.S.C. § 1367

Modern supplemental jurisdiction is primarily governed by 28 U.S.C. § 1367.

Section 1367 replaced and consolidated earlier judicial doctrines that had been described using terms such as:

• pendent jurisdiction;
• pendent-party jurisdiction; and
• ancillary jurisdiction.

The statute was enacted in 1990 as part of the Judicial Improvements Act.

The basic rule appears in § 1367(a).

It provides supplemental jurisdiction over other claims that are sufficiently related to claims within the court’s original jurisdiction so that they form part of the same Article III case or controversy.

The statute expressly states that supplemental jurisdiction may include claims involving the joinder or intervention of additional parties.

The statute then establishes important limitations in subsections (b) and (c), as well as a tolling rule in subsection (d).

Thus, § 1367 should not be read as a single unrestricted grant.

A complete analysis requires asking:

1. Does the federal court have original jurisdiction over at least one claim?
2. Are the additional claims part of the same Article III case or controversy?
3. Does § 1367(b) impose a limitation?
4. Does another federal statute restrict supplemental jurisdiction?
5. Should the court decline jurisdiction under § 1367(c)?
6. What happens to the statute of limitations if the federal court declines jurisdiction?

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4. Original Jurisdiction Must Exist First

Supplemental jurisdiction cannot exist in a vacuum.

There must first be an action over which the federal district court has original jurisdiction.

Original jurisdiction commonly comes from:

• federal-question jurisdiction under § 1331;
• diversity jurisdiction under § 1332; or
• another federal statute conferring original jurisdiction.

For example, suppose a plaintiff files a complaint containing only a state-law negligence claim between citizens of the same state.

There is no federal question.

There is no diversity jurisdiction.

The plaintiff cannot invoke supplemental jurisdiction simply because the negligence claim happens to resemble a claim that might sometimes appear in federal court.

There must be an anchor claim within the court’s original jurisdiction.

This produces an important principle:

Supplemental jurisdiction supplements original jurisdiction; it does not create the original jurisdiction that the case otherwise lacks.

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5. Supplemental Jurisdiction in Federal-Question Cases

Supplemental jurisdiction frequently appears in cases involving federal-question jurisdiction.

Suppose a plaintiff sues a police officer under a federal civil-rights statute and also asserts state-law assault and battery claims based on the same incident.

The federal civil-rights claim may provide original federal-question jurisdiction.

The state-law claims ordinarily do not arise under federal law.

Nevertheless, the federal court may exercise supplemental jurisdiction over them if they are sufficiently related to the federal claim.

This situation reflects the traditional doctrine of pendent jurisdiction, which existed before § 1367 was enacted.

The Supreme Court’s foundational decision was United Mine Workers of America v. Gibbs, 383 U.S. 715 (1966).

The Court explained that federal courts could hear state-law claims when the federal and state claims derived from a common nucleus of operative fact such that a plaintiff would ordinarily be expected to try them all in one judicial proceeding.

The modern statutory formulation is expressed through the language of the same case or controversy under Article III.

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6. The Same Case or Controversy Requirement

The central requirement of § 1367(a) is that the additional claim must be sufficiently related to the claim within the court’s original jurisdiction.

The claims must form part of the same Article III case or controversy.

This requirement is constitutional as well as statutory.

The Supreme Court’s decision in Gibbs remains important to understanding the concept. The modern statute codifies and expands the earlier doctrines under a unified statutory framework.

Cornell Law School’s discussion of supplemental jurisdiction explains the relationship between supplemental jurisdiction and the requirement that the claims form part of the same case or controversy.

The question is therefore not merely whether two claims involve the same defendant.

The more important inquiry is whether they arise from a sufficiently common factual foundation.

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7. The Common Nucleus of Operative Fact

The phrase common nucleus of operative fact comes from Gibbs and remains one of the most useful ways to understand supplemental jurisdiction.

Imagine that a customer enters a store and slips on a wet floor.

The customer brings a federal claim based on a federal statute and also asserts a state negligence claim arising from the same fall.

The claims involve overlapping:

• witnesses;
• photographs;
• medical records;
• accident reports;
• factual allegations;
• causation issues; and
• evidence concerning the defendant’s conduct.

The claims therefore have a strong factual relationship.

By contrast, imagine that the same plaintiff has an unrelated state-law dispute with the defendant concerning a contract signed ten years earlier.

The fact that the claims involve the same defendant does not necessarily make them part of the same case or controversy.

The factual relationship matters.

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8. Supplemental Jurisdiction Is Claim-Based

It is important to distinguish supplemental jurisdiction from the court’s general power over the parties.

A federal court may have personal jurisdiction over every defendant in a case and still lack supplemental jurisdiction over a particular claim.

Likewise, the existence of supplemental jurisdiction over one claim does not automatically establish supplemental jurisdiction over every conceivable claim between the parties.

The inquiry is claim-specific.

The court asks whether the additional claim is sufficiently related to the claim or claims within its original jurisdiction.

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9. Supplemental Jurisdiction and Federal-Question Claims

In federal-question cases, supplemental jurisdiction is often relatively straightforward.

Suppose a plaintiff alleges that a defendant violated federal employment law and, based on the same conduct, also alleges:

• state-law wrongful termination;
• state-law retaliation;
• breach of an employment agreement; and
• state-law emotional-distress claims.

If the claims arise from the same employment dispute, they may form part of the same Article III case or controversy.

The federal court therefore may have supplemental jurisdiction over the state-law claims.

But the word may remains important.

Section 1367(a) provides the jurisdictional basis, but § 1367(c) permits the federal court to decline supplemental jurisdiction under specified circumstances.

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10. Supplemental Jurisdiction and Diversity Jurisdiction

Supplemental jurisdiction also operates in diversity cases, but the analysis becomes more complicated.

Suppose a plaintiff from State A sues a defendant from State B.

The plaintiff’s claim exceeds $75,000, satisfying the amount-in-controversy requirement for diversity jurisdiction.

The plaintiff also brings a second state-law claim arising from the same underlying events, but the second claim is worth only $20,000.

The fact that the second claim does not independently exceed $75,000 does not necessarily prevent the federal court from hearing it.

Section 1367 can provide supplemental jurisdiction over related claims.

The Supreme Court addressed this issue in Exxon Mobil Corp. v. Allapattah Services, Inc., 545 U.S. 546 (2005).

The Court held that when at least one plaintiff satisfies the amount-in-controversy requirement and the other requirements for diversity jurisdiction are satisfied, § 1367 can permit supplemental jurisdiction over related claims by other diverse plaintiffs that do not independently meet the jurisdictional amount.

See Exxon Mobil Corp. v. Allapattah Services, Inc. on Cornell Law School’s Legal Information Institute.

This case is particularly important because it demonstrates that the amount-in-controversy requirement must be analyzed together with § 1367 rather than mechanically applied to every claim in the complaint.

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11. Supplemental Jurisdiction Does Not Destroy the Requirement of Complete Diversity

A critical limitation must be understood.

Supplemental jurisdiction does not generally permit a plaintiff to use § 1367 to circumvent the basic complete-diversity requirement.

For example, suppose:

• Plaintiff is a citizen of State A;
• Defendant 1 is a citizen of State B; and
• Defendant 2 is also a citizen of State A.

If the plaintiff’s claims against both defendants are asserted in a diversity-only action, the presence of Defendant 2 may destroy complete diversity.

The plaintiff cannot ordinarily say:

“The claim against Defendant 1 is diverse, so supplemental jurisdiction allows the claim against Defendant 2.”

The problem is that complete diversity is an element of the original diversity jurisdiction itself.

Section 1367 does not provide a general mechanism for curing a lack of complete diversity.

Instead, § 1367(b) specifically limits supplemental jurisdiction in diversity-only cases.

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12. Section 1367(b): Special Limits in Diversity Cases

Section 1367(b) is one of the most important provisions to understand.

It applies when the federal court’s original jurisdiction is based solely on § 1332, the diversity statute.

In those cases, Congress restricted supplemental jurisdiction over certain claims involving additional parties when exercising supplemental jurisdiction would be inconsistent with the requirements of diversity jurisdiction.

The statute specifically refers to certain claims involving parties joined or intervening under:

• Rule 14;
• Rule 19;
• Rule 20; and
• Rule 24.

It also addresses certain claims by persons proposed to be joined as plaintiffs under Rules 19 and 24.

The purpose is to prevent supplemental jurisdiction from being used as a device to circumvent the statutory requirements of diversity jurisdiction.

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13. Why Section 1367(b) Matters

Suppose a plaintiff files a diversity action against a defendant.

The plaintiff and defendant are completely diverse.

The plaintiff then seeks to add another defendant who is a citizen of the same state as the plaintiff.

If the additional claim could simply be brought under § 1367(a) without restriction, the plaintiff could potentially use supplemental jurisdiction to accomplish indirectly what § 1332 does not permit directly.

Section 1367(b) limits that possibility.

The statutory structure is therefore important:

Section 1367(a) creates broad supplemental jurisdiction.

Section 1367(b) limits that jurisdiction in certain diversity-only cases.

Section 1367(c) permits courts to decline jurisdiction for discretionary reasons.

Section 1367(d) protects certain claims from statute-of-limitations problems when supplemental jurisdiction is declined.

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14. The Difference Between § 1367(b) and § 1367(c)

These two subsections perform very different functions.

Section 1367(b)

Section 1367(b) establishes a statutory limitation applicable to certain diversity cases.

If its conditions are satisfied, the court lacks supplemental jurisdiction over the specified claim.

Section 1367(c)

Section 1367(c), by contrast, gives the court discretion to decline jurisdiction even when supplemental jurisdiction exists under § 1367(a).

This distinction is essential.

A claim may satisfy § 1367(a), survive § 1367(b), and nevertheless be dismissed from federal court under § 1367(c).

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15. When May a Court Decline Supplemental Jurisdiction?

Section 1367(c) identifies four circumstances in which a district court may decline supplemental jurisdiction.

They are:

1. the claim raises a novel or complex issue of state law;
2. the state-law claim substantially predominates over the federal claims;
3. the district court has dismissed all claims over which it had original jurisdiction; or
4. exceptional circumstances provide other compelling reasons for declining jurisdiction.

These provisions preserve judicial discretion.

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16. Novel or Complex State-Law Issues

Federal courts sometimes encounter state-law claims involving unsettled or particularly complicated questions of state law.

For example, suppose a federal lawsuit contains a relatively straightforward federal claim but also asks the federal court to resolve an unusually complex issue concerning a state’s developing property or regulatory law.

The federal court may determine that the state courts should resolve that question.

This reflects federalism.

State courts are generally better positioned to interpret and develop their own state’s law.

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17. When State Claims Substantially Predominate

A federal court may also decline supplemental jurisdiction when the state-law claims substantially predominate over the federal claims.

Imagine a lawsuit containing:

• one relatively minor federal claim; and
• fifteen extensive state-law claims involving the central factual and legal issues in the litigation.

Although the claims may satisfy § 1367(a), the state claims may effectively become the real substance of the case.

A federal court may conclude that the state-law issues substantially predominate and that state court is the more appropriate forum.

This is not an automatic rule.

The court must consider the circumstances of the litigation.

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18. When All Federal Claims Are Dismissed

One of the most common supplemental-jurisdiction issues arises when the federal claims disappear.

Suppose a plaintiff files:

• a federal claim; and
• several related state-law claims.

The federal court dismisses the federal claim at an early stage.

The state-law claims remain.

The court then has discretion under § 1367(c)(3) to decline supplemental jurisdiction over the remaining state-law claims.

The result is often a remand or dismissal of the state-law claims, depending on how the case reached federal court and the procedural circumstances.

The important point is that the disappearance of the original-jurisdiction claims does not necessarily mean that the federal court must continue hearing the state claims.

Instead, the court must consider whether it should retain them.

The Supreme Court has repeatedly recognized the importance of this discretionary decision.

In City of Chicago v. International College of Surgeons, the Court explained that § 1367 codifies the principles of pendent and ancillary jurisdiction while preserving judicial discretion to decline supplemental jurisdiction in appropriate circumstances. The Cornell Law School version of the decision provides the relevant discussion.

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19. The Timing of Dismissal Matters

The procedural stage at which the federal claims disappear can affect the supplemental-jurisdiction analysis.

If federal claims are dismissed at the beginning of litigation, relatively little federal judicial resources may have been invested.

The court may therefore be more inclined to allow state-law issues to proceed in state court.

If the federal court has already conducted extensive discovery, resolved numerous motions, held a lengthy trial, or otherwise invested substantial resources, the practical considerations may be different.

The court may consider:

• judicial economy;
• convenience;
• fairness;
• comity;
• the stage of litigation; and
• the relationship between the remaining claims and the dismissed federal claims.

Supplemental jurisdiction is therefore not merely a mechanical statutory calculation.

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20. Federalism and Supplemental Jurisdiction

Supplemental jurisdiction reflects the tension between two important principles.

The first is judicial efficiency.

Related claims should often be resolved together.

The second is federalism.

Federal courts should not unnecessarily decide difficult questions of state law when state courts are the institutions primarily responsible for interpreting that law.

The doctrine attempts to balance both interests.

The existence of supplemental jurisdiction therefore does not mean that federal courts should automatically exercise it whenever they have the power to do so.

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21. Supplemental Jurisdiction and the Erie Doctrine

Supplemental jurisdiction should also be distinguished from the question of which law applies.

Suppose a federal court exercises supplemental jurisdiction over a state-law claim.

The fact that the claim is being heard in federal court does not transform the underlying state-law claim into federal law.

In a diversity case, and generally with respect to state-law claims governed by the Erie doctrine, the federal court may be required to apply the relevant state’s substantive law while using applicable federal procedural law.

Thus:

Jurisdiction asks whether the federal court may hear the claim.

Choice-of-law and Erie principles ask what substantive law the federal court should apply.

These are separate questions.

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22. Supplemental Jurisdiction and Removal

Supplemental jurisdiction can also become important after removal.

A defendant may remove a case from state court when federal jurisdiction exists.

Once the action is in federal court, the federal court must determine the jurisdictional status of the claims.

A case may contain:

• a claim within federal-question jurisdiction;
• related state-law claims within supplemental jurisdiction; and
• perhaps other claims that fall outside both original and supplemental jurisdiction.

The removal statutes contain additional rules governing such situations.

Therefore, supplemental jurisdiction should be analyzed separately from the question of whether removal itself was proper.

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23. Supplemental Jurisdiction and Remand

If a federal court determines that a removed state-law claim does not fall within its original or supplemental jurisdiction, the procedural consequences may depend on the removal statute and the circumstances of the case.

In some situations, a federal court may retain the federal claims while addressing unrelated claims differently.

In others, remand may be appropriate.

The important principle is that removal does not automatically place every claim in federal court within federal jurisdiction.

Each claim must have an appropriate jurisdictional basis.

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24. Supplemental Jurisdiction Over Additional Parties

Section 1367(a) expressly provides that supplemental jurisdiction can include claims involving the joinder or intervention of additional parties.

This was significant because earlier doctrines sometimes treated claims involving additional parties differently from claims between existing parties.

Congress created a broader statutory framework.

The Supreme Court’s decision in Exxon Mobil v. Allapattah emphasized the breadth of § 1367(a), while also recognizing the specific limitations Congress imposed in § 1367(b).

This means that the phrase “supplemental jurisdiction” should not be understood as limited exclusively to additional claims against an existing defendant.

Under the statute, additional parties may also become relevant.

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25. Pendent Jurisdiction and Ancillary Jurisdiction

Older cases often use terminology that can be confusing to modern readers.

Before § 1367, federal courts developed related doctrines called pendent jurisdiction and ancillary jurisdiction.

Pendent jurisdiction generally involved additional claims related to a claim within federal jurisdiction, particularly state-law claims accompanying federal claims.

Ancillary jurisdiction developed in connection with matters related to claims already properly before the federal court, including certain counterclaims, crossclaims, and party-related matters.

Congress consolidated these doctrines under the modern term supplemental jurisdiction.

Cornell’s explanation of pendent jurisdiction describes how the earlier doctrine developed and was ultimately incorporated into § 1367.

For modern practice, § 1367 should generally be the starting point.

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26. Compulsory Counterclaims and Supplemental Jurisdiction

Supplemental jurisdiction is especially relevant to certain counterclaims.

A compulsory counterclaim arises from the same transaction or occurrence as the opposing party’s claim.

Because of this close factual relationship, a compulsory counterclaim may fall within the same Article III case or controversy.

The jurisdictional analysis can therefore involve supplemental jurisdiction when the counterclaim does not independently satisfy federal subject-matter jurisdiction.

This demonstrates why supplemental jurisdiction is not simply a doctrine for plaintiffs adding state-law claims.

It can affect claims introduced by other parties as well.

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27. Supplemental Jurisdiction Does Not Cure Every Jurisdictional Defect

A common mistake is to treat § 1367 as a general “fix” for jurisdictional problems.

It is not.

Supplemental jurisdiction cannot ordinarily cure:

• the complete absence of original federal jurisdiction;
• a failure of complete diversity where complete diversity is required;
• a statutory prohibition on federal jurisdiction;
• a lack of Article III case or controversy; or
• another independent jurisdictional defect that prevents the court from exercising authority over the action.

The proper sequence is therefore important.

The court first identifies the basis of original jurisdiction.

Only then does it examine supplemental jurisdiction.

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28. The Relationship Between Supplemental Jurisdiction and Standing

Standing and supplemental jurisdiction are also distinct.

Standing concerns whether a plaintiff has suffered the type of injury necessary to invoke federal judicial power under Article III.

Supplemental jurisdiction concerns whether additional claims are sufficiently related to claims already within the federal court’s jurisdiction.

A plaintiff cannot use supplemental jurisdiction to manufacture standing that does not otherwise exist.

There must first be a constitutionally valid case or controversy.

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29. The Relationship Between Supplemental Jurisdiction and Personal Jurisdiction

Personal jurisdiction and supplemental jurisdiction answer different questions.

Personal jurisdiction asks whether the court has authority over the defendant.

Subject-matter jurisdiction asks whether the court has authority to hear the type of dispute.

Supplemental jurisdiction asks whether additional related claims fall within the court’s statutory and constitutional authority once original jurisdiction exists.

A court may therefore have:

• personal jurisdiction over a defendant;
• original subject-matter jurisdiction over one claim; and
• supplemental jurisdiction over another claim.

These concepts should not be collapsed into one general idea of “jurisdiction.”

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30. Section 1367(d): Tolling the Statute of Limitations

Section 1367 contains an important protection for plaintiffs whose supplemental claims are dismissed from federal court.

Under § 1367(d), the limitations period for a claim asserted under § 1367 is generally tolled while the claim is pending and for 30 days after it is dismissed, unless state law provides a longer tolling period.

This matters because a plaintiff may reasonably believe that a state-law claim can proceed in federal court under supplemental jurisdiction.

If the federal court later declines supplemental jurisdiction, the plaintiff should not ordinarily lose the state-law claim merely because the federal litigation consumed the limitations period.

The Supreme Court addressed the meaning of § 1367(d) in Artis v. District of Columbia.

The provision therefore creates an important bridge between federal procedural jurisdiction and state-law limitations periods.

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31. What Happens When Supplemental Jurisdiction Is Declined?

When a federal court declines supplemental jurisdiction over a state-law claim, several procedural possibilities can arise.

If the claim originally belonged in state court and the case reached federal court through removal, the court may remand the claim when the governing removal statute permits.

If the claim was originally filed in federal court, the court may dismiss it without prejudice so that it can potentially be pursued in state court.

The precise procedural result depends on:

• how the case entered federal court;
• the applicable removal statute;
• whether the federal claims remain;
• whether dismissal is with or without prejudice;
• applicable state law; and
• the court’s order.

The tolling protection of § 1367(d) can become especially important at this stage.

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32. Supplemental Jurisdiction Is Not Mandatory in Every Practical Sense

Section 1367(a) uses broad mandatory language: when its conditions are satisfied, supplemental jurisdiction exists.

But that does not mean every qualifying claim must ultimately be adjudicated in federal court.

Section 1367(c) gives district courts authority to decline jurisdiction in specified circumstances.

The Supreme Court has recognized that this discretionary component is an important part of the doctrine.

The result is a two-stage analysis:

First: Does supplemental jurisdiction exist?

Second: If it exists, should the federal court exercise it?

That distinction is fundamental.

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33. A Practical Example

Consider the following case.

Maria, a citizen of Florida, sues a corporation that is a citizen of New York.

She alleges that the corporation negligently manufactured a product that injured her.

Her damages are $150,000.

She also asserts a second state-law claim arising from the same accident involving $10,000 in additional damages.

The first claim satisfies diversity jurisdiction because:

• the parties are completely diverse; and
• the amount in controversy exceeds $75,000.

The second claim independently falls below the $75,000 threshold.

Nevertheless, the second claim may fall within supplemental jurisdiction because it arises from the same accident and therefore may form part of the same Article III case or controversy.

The court would then ask whether any limitation under § 1367(b) applies and whether any reason exists under § 1367(c) to decline jurisdiction.

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34. Another Example: Federal Employment Claim

Suppose an employee sues an employer alleging:

1. violation of a federal employment statute;
2. state-law wrongful termination;
3. state-law breach of contract; and
4. state-law defamation arising from statements made during the termination process.

If the claims arise from substantially the same employment dispute, the state claims may fall within supplemental jurisdiction.

But imagine the employee also adds a completely unrelated state-law claim concerning a business transaction with the same employer that occurred five years earlier.

The fact that the defendant is the same does not automatically establish supplemental jurisdiction.

The unrelated business dispute may not form part of the same Article III case or controversy.

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35. Another Example: Diversity and an Additional Plaintiff

Suppose two plaintiffs sue a defendant in federal court based on diversity jurisdiction.

Plaintiff A satisfies the $75,000 amount-in-controversy requirement.

Plaintiff B has a related claim worth only $30,000.

Under Exxon Mobil v. Allapattah, § 1367 may permit the federal court to exercise supplemental jurisdiction over Plaintiff B’s related claim, assuming the other diversity requirements are satisfied and no statutory limitation applies.

This is an important example of why the amount-in-controversy requirement should not be applied mechanically to every individual claim.

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36. A Structured Method for Analyzing Supplemental Jurisdiction

A useful exam and practice framework is to proceed in stages.

Step 1: Identify the original-jurisdiction claim

Ask:

What gives the federal court original jurisdiction?

Is it:

• federal question;
• diversity;
• another federal statute; or
• something else?

If there is no original jurisdiction, stop.

Supplemental jurisdiction cannot independently create the required original jurisdiction.

Step 2: Identify the additional claim

Determine exactly which claim lacks an independent federal jurisdictional basis.

Step 3: Compare the factual foundations

Ask whether the claims arise from substantially the same events, evidence, witnesses, transactions, or factual disputes.

Step 4: Apply the Article III case-or-controversy requirement

Determine whether the claims are sufficiently related to form one constitutional case or controversy.

Step 5: Examine § 1367(b)

If original jurisdiction is based solely on diversity, determine whether the specific claim or party relationship falls within the restrictions of § 1367(b).

Step 6: Consider other statutory restrictions

Another federal statute may independently limit federal jurisdiction.

Step 7: Consider § 1367(c)

Even if supplemental jurisdiction exists, determine whether the court may decline it.

Step 8: Consider procedural consequences

If jurisdiction is declined, determine whether the claim should be dismissed, remanded, or otherwise transferred according to the applicable procedural framework.

Step 9: Check the statute of limitations

Consider § 1367(d) and any applicable state tolling rules.

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37. Common Mistakes About Supplemental Jurisdiction

Mistake 1: Treating supplemental jurisdiction as original jurisdiction

Supplemental jurisdiction does not replace the requirement for original jurisdiction.

Mistake 2: Assuming every claim against the same defendant qualifies

The claims must be sufficiently related.

Mistake 3: Ignoring § 1367(b)

Diversity cases require special attention to the statutory limitations.

Mistake 4: Assuming supplemental jurisdiction is always exercised

The court may decline jurisdiction under § 1367(c).

Mistake 5: Confusing supplemental jurisdiction with personal jurisdiction

They concern different forms of judicial authority.

Mistake 6: Assuming a small claim can never enter federal court

A claim below the normal diversity amount may sometimes fall within supplemental jurisdiction when the statutory requirements are satisfied.

Mistake 7: Assuming dismissal of the federal claim automatically ends every remaining claim

The court must analyze § 1367(c), the procedural posture, and the circumstances of the case.

Mistake 8: Ignoring the statute of limitations

Section 1367(d) can be critical when supplemental claims are dismissed.

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38. Supplemental Jurisdiction and Judicial Economy

One of the strongest practical reasons for supplemental jurisdiction is judicial economy.

Suppose a federal court has already heard extensive evidence about an automobile accident.

If the plaintiff’s state-law negligence claim and federal claim arise from the same accident, requiring another court to hear the state claim could duplicate much of the work.

Supplemental jurisdiction can allow one court to resolve the dispute as a whole.

This can reduce:

• duplicative discovery;
• litigation costs;
• inconsistent factual findings;
• repeated testimony; and
• unnecessary judicial expenditure.

But judicial economy is balanced against federalism and the limited role of federal courts.

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39. Supplemental Jurisdiction and Fairness

Fairness to litigants is another important consideration.

A plaintiff may reasonably expect closely connected claims to be resolved in one proceeding.

A defendant may similarly benefit from avoiding multiple lawsuits involving the same facts.

At the same time, retaining a complicated state-law dispute in federal court may sometimes impose costs on the parties and the judiciary.

The discretionary nature of § 1367(c) allows courts to account for these competing considerations.

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40. Supplemental Jurisdiction and Comity

Comity refers broadly to respect for the authority and institutional interests of state courts.

Federal courts routinely interpret state law, especially in diversity cases.

But when a supplemental claim presents a novel or particularly difficult question of state law, a federal court may decide that the state’s courts should have the opportunity to resolve it.

This is one reason § 1367(c)(1) expressly identifies novel or complex state-law issues as a basis for declining jurisdiction.

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41. The Constitutional Dimension

Supplemental jurisdiction ultimately rests on Article III’s concept of a judicial “case” or “controversy.”

The Constitution defines the outer boundary of federal judicial power.

Congress then determines through statutes how federal courts may exercise that constitutional authority.

Section 1367 is therefore a statutory implementation of supplemental jurisdiction within constitutional limits.

The Supreme Court’s jurisprudence, including Gibbs and later decisions interpreting § 1367, explains the relationship between the constitutional case-or-controversy requirement and the statutory grant.

For a broader constitutional perspective, Cornell Law School’s Constitution Annotated discussion of supplemental jurisdiction provides useful background.

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42. The Historical Development of Supplemental Jurisdiction

The modern doctrine did not appear fully formed.

Earlier federal cases developed related concepts through judicial decisions.

In United Mine Workers v. Gibbs, the Supreme Court articulated the common-nucleus-of-operative-fact approach to pendent claims.

Later cases considered the extent to which federal courts could exercise jurisdiction over claims involving additional parties.

Congress eventually enacted § 1367 in 1990.

The statute brought the major doctrines together under one statutory framework.

This history explains why older cases may use terminology that differs from modern statutory language.

For students of civil procedure, however, the practical starting point is § 1367.

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43. Supplemental Jurisdiction After Exxon Mobil

Exxon Mobil v. Allapattah is particularly important for understanding how § 1367 operates in diversity cases.

The Court interpreted § 1367(a) broadly enough to permit supplemental jurisdiction over claims of additional diverse plaintiffs that did not independently satisfy the amount-in-controversy requirement, provided at least one plaintiff satisfied that requirement and the other jurisdictional requirements were met.

The decision illustrates an important methodological point:

Do not analyze § 1332 in isolation when multiple related claims or parties are involved.

A proper jurisdictional analysis may require reading §§ 1332 and 1367 together.

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44. Supplemental Jurisdiction in Class Actions

Supplemental jurisdiction can become particularly important in complex litigation involving multiple plaintiffs.

Exxon Mobil itself involved a class-action context.

In addition, the Class Action Fairness Act of 2005 created separate jurisdictional rules for many qualifying class actions.

Therefore, a class action should not automatically be analyzed under ordinary individual diversity principles.

When CAFA applies, the relevant statutory framework must be examined separately.

The existence of § 1367 does not eliminate the need to identify any special jurisdictional statute governing the case.

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45. The Difference Between Supplemental Jurisdiction and Joinder

Joinder and supplemental jurisdiction are closely related but distinct.

Joinder concerns whether parties or claims may be brought together in one lawsuit under the Federal Rules of Civil Procedure.

Supplemental jurisdiction concerns whether the federal court has subject-matter jurisdiction over those claims once they are joined.

A claim may be procedurally permissible to join but still lack an adequate jurisdictional basis.

Conversely, a claim may fall within supplemental jurisdiction but still have to satisfy procedural requirements for joinder.

Civil procedure therefore requires both analyses.

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46. The Difference Between Supplemental Jurisdiction and Venue

Venue determines the appropriate geographic federal district.

Supplemental jurisdiction determines whether the federal court may hear an additional related claim.

A claim can fall within supplemental jurisdiction but still raise a venue problem.

Likewise, proper venue does not establish supplemental jurisdiction.

These are separate procedural doctrines.

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47. Supplemental Jurisdiction and the Merits

Jurisdiction must also be distinguished from the merits.

A federal court may have supplemental jurisdiction over a state-law claim even if the plaintiff ultimately cannot prove the claim.

For example, the court may have jurisdiction over a state negligence claim because it arises from the same facts as a federal claim.

If the plaintiff fails to prove negligence, the court may enter judgment for the defendant.

The existence of jurisdiction does not imply that the plaintiff will win.

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48. A Useful Conceptual Formula

For practical purposes, supplemental jurisdiction can be remembered through the following conceptual formula:

Original federal jurisdiction + related claim + same Article III case or controversy + no statutory prohibition + no discretionary refusal = supplemental jurisdiction may be exercised.

The formula should not be treated as a substitute for reading § 1367.

But it provides a useful mental framework.

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49. Key Takeaways

Supplemental jurisdiction is one of the mechanisms that allows federal courts to resolve an entire dispute rather than dividing closely connected claims between federal and state courts.

The most important principles are:

1. Supplemental jurisdiction is primarily governed by 28 U.S.C. § 1367.
2. There must first be original federal jurisdiction over at least one claim.
3. The additional claims must form part of the same Article III case or controversy.
4. The traditional “common nucleus of operative fact” formulation from Gibbs remains highly useful.
5. Supplemental jurisdiction can include claims involving additional parties.
6. Section 1367(b) imposes special limitations in diversity-only cases.
7. Section 1367(c) permits federal courts to decline supplemental jurisdiction in specified circumstances.
8. The dismissal of all original-jurisdiction claims often creates a reason to reconsider supplemental jurisdiction.
9. Section 1367(d) provides important tolling protection for certain claims when supplemental jurisdiction is declined.
10. Supplemental jurisdiction is different from personal jurisdiction, venue, standing, and the merits.
11. A related claim does not automatically belong in federal court simply because it involves the same defendant.
12. Diversity cases require especially careful analysis of §§ 1332 and 1367 together.

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50. Frequently Asked Questions

What is supplemental jurisdiction?

Supplemental jurisdiction allows a federal court to hear additional claims that do not independently satisfy federal subject-matter jurisdiction requirements when those claims are sufficiently related to claims already within the court’s original jurisdiction.

What statute governs supplemental jurisdiction?

The primary statute is 28 U.S.C. § 1367.

Does supplemental jurisdiction require original federal jurisdiction?

Yes. A federal court must have original jurisdiction over at least one claim before supplemental jurisdiction can operate.

What does “same case or controversy” mean?

The additional claim must be sufficiently related to the claim within the court’s original jurisdiction to form part of the same constitutional Article III case or controversy.

What is the common nucleus of operative fact?

It is the traditional formulation associated with United Mine Workers v. Gibbs. Claims generally satisfy the concept when they arise from substantially overlapping facts and would ordinarily be expected to be litigated together.

Can supplemental jurisdiction apply to state-law claims?

Yes. This is one of its most common applications.

Can supplemental jurisdiction apply in diversity cases?

Yes. However, § 1367(b) imposes important restrictions in cases where original jurisdiction is based solely on diversity.

Can a claim worth less than $75,000 be heard in federal court?

Potentially. A claim that does not independently satisfy the diversity amount-in-controversy requirement may sometimes fall within supplemental jurisdiction if the statutory requirements are satisfied.

Can supplemental jurisdiction cure a lack of complete diversity?

Generally no. Supplemental jurisdiction does not provide a general method for circumventing the complete-diversity requirement of § 1332.

Can a federal court refuse supplemental jurisdiction?

Yes. Section 1367(c) identifies circumstances in which a federal court may decline to exercise supplemental jurisdiction.

What happens if the federal claim is dismissed?

The federal court may decline supplemental jurisdiction over remaining state-law claims, particularly when all claims supporting original jurisdiction have been dismissed. The court must consider the circumstances and the factors relevant to § 1367(c).

Does declining supplemental jurisdiction mean the state claim is permanently lost?

Not necessarily. Depending on the procedural circumstances, the claim may be pursued in state court. Section 1367(d) may also toll the applicable limitations period while the claim is pending and for at least 30 days after dismissal, subject to the statute’s terms and any longer state tolling period.

What is the difference between supplemental and personal jurisdiction?

Personal jurisdiction concerns the court’s authority over a defendant or other party. Supplemental jurisdiction concerns the court’s subject-matter jurisdiction over additional claims related to claims already within its original jurisdiction.

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Conclusion

Supplemental jurisdiction is one of the central doctrines connecting the constitutional limits of federal judicial power with the practical realities of modern litigation.

Federal lawsuits frequently contain multiple claims arising from the same transaction, occurrence, or factual dispute. Some may arise under federal law, while others arise under state law. Some may independently satisfy diversity jurisdiction, while others may not. Without supplemental jurisdiction, many such disputes would have to be fragmented between separate courts.

Section 1367 provides a framework for keeping related claims together when they form part of the same Article III case or controversy. At the same time, Congress has preserved important safeguards. Section 1367(b) restricts supplemental jurisdiction in specified diversity cases, while § 1367(c) allows federal courts to decline jurisdiction when state-law issues predominate, become unusually complex, or otherwise make federal adjudication inappropriate.

The most important conceptual distinction is therefore between power and discretion. A claim may fall within supplemental jurisdiction without necessarily being retained in federal court. The court must first determine whether supplemental jurisdiction exists and then determine whether exercising it is appropriate.

For civil procedure, the essential sequence is straightforward:

Original jurisdiction first. Relatedness second. Statutory limitations third. Judicial discretion fourth.

Understanding that sequence makes supplemental jurisdiction much easier to analyze—and provides the foundation for understanding how federal courts manage lawsuits containing both federal and state-law claims.

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